Long term fuel trims maxed at+25%, what does this mean? - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 69 Old 07-10-2002, 01:46 AM Thread Starter
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Question Long term fuel trims maxed at+25%, what does this mean?

Was looking at something with the autotap tonight and I noticed that my long term fuel trims are both maxed at +25%. My short term trims are fine, hovering right around 0% like they should. I'm wondering why my long terms are so outta whack (maybe this is why my gas mileage sucks right now, like 10mpg).

I've been dyno tuned and all, so my a/f is good, but this problem concerns me. I wonder if it's related to my other problem (fuel pressure surges erradically unless my fan switch is on, see thread here).


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post #2 of 69 Old 07-10-2002, 09:13 AM
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Re: Long term fuel trims maxed at+25%, what does this mean?

Quote:
Originally posted by 99SaleenS281
Was looking at something with the autotap tonight and I noticed that my long term fuel trims are both maxed at +25%. My short term trims are fine, hovering right around 0% like they should. I'm wondering why my long terms are so outta whack (maybe this is why my gas mileage sucks right now, like 10mpg).

I've been dyno tuned and all, so my a/f is good, but this problem concerns me. I wonder if it's related to my other problem (fuel pressure surges erradically unless my fan switch is on, see thread here).
Can't say for sure if it is related to your fuel pressure fluctuation problem BUT as far as the LTFTs being 25% Rich (by the way 5% more STFT and you'll be throwing the "Bank X Too Lean" codes), this is an easy one. The answer is in your signature...........C&L 80mm MAF. Here's what I posted in another thread here on the Corral:

"Exactly BadBud! Just to recap, here's what happens:

1. OEM Meter is calibrated to take into account the ratio of the sampling tube cross-sectional area to main bore cross-sectional area (among other things).

2. C&L effectively alters the ratio between the sampling tube and bore area. The desired effect is that this new ratio (which isn't very accurate) makes the PCM think that it's getting less air so the PCM leans out the mixture at WOT. However, during adaptive operation, the PCM notices that the reported airflow always causes the mixture to be lean so it has to up the fuel trims (enrichen) in order to maintain stoichiometric (14.7:1 air-fuel ratio).

3. The real problem occurs after the PCM has fully adapted to the C&L meter after some miles of driving. When you finally go to test the car on a dyno you run RICH! How is this possible? Open-loop works like this more or less: the PCM looks at the mass-air meter to read air-flow, it then goes to a table and picks the correct injector pulse-width to use to yield some predetermined air-fuel ratio (also in a table). Now, it also has this thing called the Open Loop Fuel Modifier which is essentially a history of how far off the mass-air meter has been when running adaptive. Different model years do different things here BUT they are all based off of the Long-term fuel trims (LTFTs). In general, if the meter is always causing you to be lean by 8% when in closed-loop, your LTFTs will be close to +8% (RICH). Then when you go WOT and your PCM goes open-loop, 8% fuel will be added to the computed injector pulsewidth in order to get the right air-fuel ration. The BIG PROBLEM is that this +8% actually causes you to be RICH by 8% because the LTFTs have adapted to a modified and inaccurate signal!"


So, you should check your LTFTs and STFTs across the rpm/load range by logging them with an OBD-II scanner during different driving conditions. The LTFTs are not just two data values but an array of data with RPM/load as indexes.

You say you were dynotuned. What is the time relation between installation of the C&L meter and the dyno tune? IOW, was the C&L already on your car before you went to get tuned OR did you install the meter after the tune? Did you or the shop tune kill the battery power anytime right before tuning your car (clear the KAM)? If you answer yes to either of these questions, there is a chance that you are running really rich at WOT now. If not, then you are probably OK at WOT. However, when the LTFTs get pegged (25% is maximum) the system tends to behave funny when running in closed loop. Check for posts here on the Corral by "onerichrunner" where he talks about how he used the MAFterburner to correct his out of whack LTFT problems caused by his new cams. Once he started getting the fuel trims down, the PCM started doing the right thing. Until then, the PCM was doing all funky stuff with fuel and timing to get the car to idle (unsuccessfully).

Anyway, a short-term fix is to ditch the C&L and go with another meter like an 80mm or 90mm LMAF. However, this will require a retune. You could also purchase a MAFterburner (my product) and use it to correct your LTFT issue caused by the C&L meter and further optimize your WOT air-fuel curve if necessary. You can also do a search here on the Corral for "MAFterburner". There are a lot of people who have successfully used it here.

For more tech information, see: www.seanhylandmotorsport.com/mafterburner

Or, you can join our tech forum at: www.seanhylandmotorsport.com/forum

Finally, if you have any other questions, you can email me at: [email protected]

In summary, the LTFT problem you have is caused by the C&L meter. I'd bet lunch on it! It happened to me and I've seen it many other times!

Mark Chiappetta


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post #3 of 69 Old 07-10-2002, 09:22 AM
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One more quick test that you can do is the following:

1. change back over to your stock meter

2. disconnect battery (+) for at least 30minutes to kill the Keep-Alive Memory.

3. Reconnect the battery (+) and do the idle relearn procedure(idle 5min with accesories off and 5min with AC on, I think)

4. Hook up the OBD-II scanner and recheck your idle trims and your fuel pressure.

5. Do the test that you do with flipping on the FAN and see if the fuel pressure continues to fluctuate wildly.

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post #4 of 69 Old 07-10-2002, 12:32 PM
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mjchip is almost right. A MAF reports X voltage. The EEC tansfer function translates this to an airflow value. The transfer function matches the stock MAF (unless changed with a chip, etc.). You swapped MAF's, and now the transfer function doesn't match. I'm not sure if you mean the long term trim is adding 25% fuel, or pulling that much. Either way, the MAF is not reporting the correct airflow to the EEC. Because the long term trim is correcting for the problem, the short term trims appear normal. You can fix this with a chip, a maf adjuster, a MAFterBurner, etc. If you are OK at WOT you could also drop fuel pressure a few psi to get the LTFT's back within the acceptable range. THIS COULD CAUSE A LEAN CONDITION A WOT!!!!

The cross section really isn't important. It's the MAF electronics that determine what voltage to report based on the temp differential of the control wire and the hot wire.

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post #5 of 69 Old 07-10-2002, 12:45 PM
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Quote:
Originally posted by David Posea
mjchip is almost right. A MAF reports X voltage. The EEC tansfer function translates this to an airflow value. The transfer function matches the stock MAF (unless changed with a chip, etc.). You swapped MAF's, and now the transfer function doesn't match. I'm not sure if you mean the long term trim is adding 25% fuel, or pulling that much. Either way, the MAF is not reporting the correct airflow to the EEC. Because the long term trim is correcting for the problem, the short term trims appear normal. You can fix this with a chip, a maf adjuster, a MAFterBurner, etc. If you are OK at WOT you could also drop fuel pressure a few psi to get the LTFT's back within the acceptable range. THIS COULD CAUSE A LEAN CONDITION A WOT!!!!

The cross section really isn't important. It's the MAF electronics that determine what voltage to report based on the temp differential of the control wire and the hot wire.

David
David is almost right also, right up until the point where he says, "The cross section really isn't important....."

Actually, the *ratio* of the sampling tube cross-sectional area to the overall meter cross-sectional area DOES MATTER. Yes, the MAF electronics is what determines how to convert air-flow to voltage, however, the MAF electronics converts the air-flow in the sampling tube only to voltage. The transfer function in the PCM actually takes into account the ratio of both areas to determine how much mass-air flow there is through the entire meter. This is how C&L alters the MAF signal, by changing the ratio of the two cross-sectional areas.

I stand by everything that I said earlier.

Cheers,

Mark

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post #6 of 69 Old 07-10-2002, 04:27 PM
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will be running that rich on a blower car be good or bad.i have been getting codes p0171 and p0174 for a while now.i'm waiting for my scanner to get here so i can look at my fuel trims.i have a prom77 calib for 36 lb inj.i know pro m calibrate the blower aplications on the rich side,so i'm lost as to why i get system lean bank 1 and 2.i only get the codes when i turn on the ac and it happens only in close loop.i have a jms chip,but it threw codes with and without the chip.i replace the o2 sensors,but i never disconected the battery.the car is running so strong i dont want to mess with it until i get the scanner.i've my prom77 for 4 years now and it just started throwing codes the last couple months.
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post #7 of 69 Old 07-10-2002, 04:58 PM
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Mark, I thought if the OBD2 device reads +25% that was a lean condition, and -25% was a rich condition?
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post #8 of 69 Old 07-10-2002, 04:59 PM
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Quote:
Originally posted by vortech gt
will be running that rich on a blower car be good or bad.i have been getting codes p0171 and p0174 for a while now.i'm waiting for my scanner to get here so i can look at my fuel trims.i have a prom77 calib for 36 lb inj.i know pro m calibrate the blower aplications on the rich side,so i'm lost as to why i get system lean bank 1 and 2.i only get the codes when i turn on the ac and it happens only in close loop.i have a jms chip,but it threw codes with and without the chip.i replace the o2 sensors,but i never disconected the battery.the car is running so strong i dont want to mess with it until i get the scanner.i've my prom77 for 4 years now and it just started throwing codes the last couple months.
Well, on a supercharged car, rich is better than lean from a safety standpoint.

If you are getting "Bank 1 Too Lean" and "Bank 2 Too Lean" 4 years after making any other changes to your setup, the first thing I would suspect is graceful degradation of the EGO sensors. However, since you already replaced the O2 sensors (I would've disconnected the battery because the fuel trims are no longer completely accurate with new O2s) that rules out my first instinct.

There is a good chance that the Pro-M meter was calibrated lean causing your fuel trims to be very positive but not so positive that a DTC was thrown. Then, as your system normally aged, the limits were reached (+25% LTFT and +5% STFT on some model years) and the codes were thrown.

You need to get your hands on that OBD-II scanner.

Mark
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post #9 of 69 Old 07-10-2002, 05:02 PM
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Mark you have have been typing same time as me. See my question above yours.
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post #10 of 69 Old 07-10-2002, 05:03 PM
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Quote:
Originally posted by TxSnakeCharmer
Mark, I thought if the OBD2 device reads +25% that was a lean condition, and -25% was a rich condition?
You are correct. If the STFTs/LTFTs are positive, that means that the PCM needs to add fuel in order to compensate for a mass-air signal that results in a lean air-fuel ratio when monitored with the O2 sensors.

Likewise, if the STFTs/TFTs are negative, the PCM is pulling fuel out to compensate for a maf signal that causes the air-fuel ratio to be rich when monitored with the O2 sensors.

Mark

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post #11 of 69 Old 07-10-2002, 05:05 PM
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OK, just wanted to check. I follow all these A/F posts so I need to keep myself straight. So his LTFT is running super lean, not super rich.
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post #12 of 69 Old 07-10-2002, 05:06 PM Thread Starter
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Well, what you see in my sig is how I was dyno tuned. I was tuned by the Onerichrunner you mention in your post, and I even bought the C&L from him, hehe.

Hrm... what to do what to do. I don't have any money right now to buy a new meter or the MAFterburner (which I've followed closely, looks like a great product). I guess this is why a lot of people don't like C&L meters and go with ProM, since the ProM calibrated electronics report to the PCM corrently.

I'll can't swap my stock meter back in because I have 30lb injectors. The old superchip that came from vortech compensated for the stock meter w/larger injectors, however, my current chip is set-up for matched injectors and maf. I guess I can reset the pcm and see if that does anything...

Any other idea? Tell me a little about how the MAFterburner fixes LTFTs. Shawns post was regarding STFTs. I guess once you get your STFTs stable (like I said, I've only checked mine at idle, not under load), your LTFTs 0 out as well.
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Let me try to understand something else: the PCM only uses the LTFTs to adjust fuel at WOT? Is this correct? I rarely, if ever, drive WOT. 95% of my driving is below 3000 rpms.

The +25% LTFT on my car tells me it needs to add +25% fuel, which would explain my god-awful gas mileage.
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post #14 of 69 Old 07-10-2002, 05:16 PM
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Quote:
Originally posted by 99SaleenS281
Well, what you see in my sig is how I was dyno tuned. I was tuned by the Onerichrunner you mention in your post, and I even bought the C&L from him, hehe.

Hrm... what to do what to do. I don't have any money right now to buy a new meter or the MAFterburner (which I've followed closely, looks like a great product). I guess this is why a lot of people don't like C&L meters and go with ProM, since the ProM calibrated electronics report to the PCM corrently.

I'll can't swap my stock meter back in because I have 30lb injectors. The old superchip that came from vortech compensated for the stock meter w/larger injectors, however, my current chip is set-up for matched injectors and maf. I guess I can reset the pcm and see if that does anything...

Any other idea? Tell me a little about how the MAFterburner fixes LTFTs. Shawns post was regarding STFTs. I guess once you get your STFTs stable (like I said, I've only checked mine at idle, not under load), your LTFTs 0 out as well.
Wow, small world. Shawn is a good guy and he is very familiar with the MAFterburner. The best thing to do is give him a call or email him about your situation and see if he thinks that a MAFterburner will help. Tell him about the fuel pressure fluctuation and every detail. Remind him about the C&L meter too.

In your case, you would use the MAFterburner to "recalibrate" the meter to match the current MAF transfer function that is in the chip. It's similar procedure to what Shawn did with his car to get the thing to idle with the new cams. Call him.

Mark

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post #15 of 69 Old 07-10-2002, 05:24 PM
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Quote:
Originally posted by 99SaleenS281
Let me try to understand something else: the PCM only uses the LTFTs to adjust fuel at WOT? Is this correct? I rarely, if ever, drive WOT. 95% of my driving is below 3000 rpms.

The +25% LTFT on my car tells me it needs to add +25% fuel, which would explain my god-awful gas mileage.
1. The LTFTs/STFTs are used in closed-loop adaptive strategies only, NOT WOT. However, history from the LTFTs is used in the form of the Open Loop Fuel Modifier variable during WOT. Basically, if the PCM knows from evaluating the LTFTs that your MAF signal always results in an air-fuel ratio that is 10% too lean during closed-loop, it will set the OLFM = +10% so when you go WOT, you get the calculated injector pulse-width + the OLFM. In some model years the PCM takes the LTFT at 3000rpm and uses that as the OLFM. In other years, I believe, it uses an average of LTFTs between a certain rpm range as the OLFM. Either way, the system has some non-ideal characteristics that can be inadvertently be exacerbated by otherwise well-intentioned mods.

If the MAF transfer function is off 10% lean at low to mid flow rates but is accurate at high flow rates, then your air-fuel ratio may end up being 10% too rich when you at at high rpms in open-loop.

2. The +25% LTFT means that the PCM is adding 25% fuel to the calculated injector pulsewidth. Like I said earlier, if the MAF is incorrectly reporting the mass-air flow which results in this erroneous 25% rich correction, your car will run extremely rich when the PCM goes open-loop.

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Last edited by mjchip; 07-10-2002 at 05:42 PM.
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post #16 of 69 Old 07-10-2002, 10:26 PM
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So with a EEC tuner you could limit these closed loop offsets by decreasing the adaptive strategy to 5 or 10%?????

Thanks,

Shannon

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post #17 of 69 Old 07-10-2002, 11:27 PM
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Great thread!

My question: Do *all* EEC V's allow the reading of long/short term trim values? I didn't think any EEC IV's had that capability.

My comments:
1) About the gas mileage: As it is now, your misadjusted MAF does *not* affect your gas mileage *when the car is warn*. Once in closed loop, it seems like your EEC is able to run at stoic.

2) At least for the EEC IV's, RPM is used along with the MAF for calculating injector pulse width at WOT. I also thought that for the EEC IV's, the RPM is the major factor in determining the injector pulse width at WOT. That seems to contradict what I read on the MAFterburner forums.

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post #18 of 69 Old 07-11-2002, 01:14 AM
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Quote:
Originally posted by stangPlus2Birds
Great thread!

My question: Do *all* EEC V's allow the reading of long/short term trim values? I didn't think any EEC IV's had that capability.

My comments:
1) About the gas mileage: As it is now, your misadjusted MAF does *not* affect your gas mileage *when the car is warn*. Once in closed loop, it seems like your EEC is able to run at stoic.

2) At least for the EEC IV's, RPM is used along with the MAF for calculating injector pulse width at WOT. I also thought that for the EEC IV's, the RPM is the major factor in determining the injector pulse width at WOT. That seems to contradict what I read on the MAFterburner forums.
1. You are correct about mileage as the PCM should still be able to maintain stoich in closed-loop adaptive mode.

2. Here is a quote from EEC-IV notes: "The EEC does 4 point interpolation on all tables. There is a minimal number of
cells in the fuel lookup tables. The EEC doesn't look up 'injector on time', it calculates the injector pulse width by looking at the desired Lambda and then, using the mass of air entering the engine and the injector size, it calculates the duty cycle needed to get the desired A/F ratio. (Lambda is an engineering term where stoich is 1, anything smaller than 1 is rich, anything larger than 1 is lean. To get A/F numbers from Lambda, multiply lambda value by 14.64. For example, an A/F ratio of 14.05:1 is a lambda of .85 lambda.)"


Hope this helps,

Mark

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post #19 of 69 Old 07-11-2002, 02:35 AM Thread Starter
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Quote:
Originally posted by stangPlus2Birds
1) About the gas mileage: As it is now, your misadjusted MAF does *not* affect your gas mileage
My maf isn't misadjusted, it's just not accurate apparently.

Hrm, where to get $300 really quick...

Come to think of it, my first dyno pull (last month) we were lean, so we added fuel. Maybe these LTFTs are left over from my previous lean condition... how often do LTFTs get updated?
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post #20 of 69 Old 07-11-2002, 04:22 AM
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Sorry to hit the thread so late Mike. You still have that inconsistent surging fuel pressure deal?? We need to get a handle on that PITA FIRST. Remember, cure any known problems first or we can just chase our tails.

Sorry to get to the thread so late Mike. Give me a call sometime and lets try to get a handle on that fueling issue. I have 2 dynos tomorrow morning and trying to finish up the T56 in the late afternoon.

Shawn
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Quote:
Originally posted by onerichrunner
Sorry to hit the thread so late Mike. You still have that inconsistent surging fuel pressure deal?? We need to get a handle on that PITA FIRST. Remember, cure any known problems first or we can just chase our tails.

Sorry to get to the thread so late Mike. Give me a call sometime and lets try to get a handle on that fueling issue. I have 2 dynos tomorrow morning and trying to finish up the T56 in the late afternoon.

Shawn
Mike, you' re in good hands now! I'm outta here!

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Quote:
Originally posted by onerichrunner
You still have that inconsistent surging fuel pressure deal??
I'm narrowing in on it, check out the thread in EEC tech "HDEF/EDF Relays"...
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post #24 of 69 Old 07-11-2002, 05:44 PM
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Today when I was checking out Rev2 of the Autotap software , I noticed that my LT trims were +24% at idle. Using a gauge in the Windows software I noticed that it quickly went to 2% if I brought the revs up slowly. Now I know that the LT trims used to show around 2-5% at idle for the ProM75 silver bullet the last time I checked 6 months ago.
Hunted around for an air leak and found one. The hose for the PCV oil catch can was off as I bumped it loose when I emptied the PCV oil catch can last week. The air leak was into the passenger's side valve cover , through the engine, and back out the driver's side valve cover to the air intake tube. Pushed the hose back on and the idle trim numbers slowly drifted back down to 2-3%.
You may want to check for an air leak.
Winston.
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post #25 of 69 Old 07-11-2002, 09:20 PM
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I'm going to chime in here.

I have a 96GT with a DOHC motor. I am using the GT wiring harness on the engine and the GT PCM. I also have a twEECer and run a C&L 80mm MAF. Recently the car began running really horrible. I pulled the chip and it immediatlly ran better. Took the car to a Ford tech buddy of mine. I had a bad hego. With the chip in, the LTFT was 25%+. w/o the chip the LTFT began to drop. We replaced the bad hego and the LTFT with and w/o the chip came back into range.

So C&L MAF's can't be all that bad!

what?
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post #26 of 69 Old 07-11-2002, 09:42 PM
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Winston,

You need to delete the KAM when looking at the STFTs. Disconnect the battery, turn the key to the run position and tap the brakes a few times. Unless you do that the STFTs will be based upon the tweaks from the LTFTs.

Chris Yates
96 Cobra
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post #27 of 69 Old 07-11-2002, 10:39 PM
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i didn't realize there were so many people that don't know that much about what seems like they know alot about. First stft is a mirror image or the upstream hegos. if the hego is reading lean by say 5% then the stft will goto +5%. long term fuel trim is what modifies the fuel tables not the short term. 99.99% of the time a fuel trim that is out in left feild is the result of an air leak or a bad maf. i hate the c&l meter as most people that make real power do. it cost me a crank and rod on a cust. 96 cobra motor. it detonated the rod bearing out of one rod. not a oiling issue either. a + on a fuel trim says that the pcm is adding fuel and a - means it is subtracting fuel. 99saleens281 be careful who you listen to on here as i have read this complete post and most of these guys don't know as much as it looks like. to everyone else if you really know what you are doing then you shouldn't be offended. i am a ford senior master tech and a expert in drivabilty and i see this type stuff in the dealer every day, and i 99% of the time fix their cars with one part, the bad part not by replacing everything until i fix it. i have 42#ers in my 5.0 ranger with a 90mm maf and absolutly no drivabilty problems. the pcm is very smart in ways and also very stupid in other ways. aslong as you give it the input that it wants to see for the situation that is hapening then it will run like factory. plus my cam has 544 lift and 228 int and 238 exh at .050 yes it cams hard but no drivablity problems from the cam so i say B.S. to most of the post on this fourm. most anyone can tune for max power at wot but the real tunners make max safe power and also tune for the everyday drivablity. so 98saleen i will not reply to this thread again so if you want my advise then e-mail me. Tim
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post #28 of 69 Old 07-11-2002, 10:50 PM
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Quote:
Originally posted by Chris Yates
Winston,

You need to delete the KAM when looking at the STFTs. Disconnect the battery, turn the key to the run position and tap the brakes a few times. *** Unless you do that the STFTs will be based upon the tweaks from the LTFTs. ***

Chris Yates
96 Cobra
Hey Chris,

Could you clarify this (the phrase surrounded by asterisks)? It's a little cryptic.

Mark
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post #29 of 69 Old 07-11-2002, 11:40 PM
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Mark,

I might have it wrong but I was under the impression that as the LTFT are established the STFT's would get closer to zero. For example, let's say the car is running STFT's of 25%, over time I though the LTFT would work towards 25% as the EEC works out the lean condition. Then the STFTs will get closer to 0. I'm following the directions posted here: http://www.iwantperformance.net/cgi-...c&f=1&t=000020

They recommend you disable adaptive control and kill the existing LTFTs by unhooking the battery.

Thanks,

Chris Yates
96 Cobra
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post #30 of 69 Old 07-12-2002, 03:46 AM
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Originally posted by v8ranger
i didn't realize there were so many people that don't know that much about what seems like they know alot about. First stft is a mirror image or the upstream hegos. if the hego is reading lean by say 5% then the stft will goto +5%. long term fuel trim is what modifies the fuel tables not the short term. 99.99% of the time a fuel trim that is out in left feild is the result of an air leak or a bad maf. i hate the c&l meter as most people that make real power do. it cost me a crank and rod on a cust. 96 cobra motor. it detonated the rod bearing out of one rod. not a oiling issue either. a + on a fuel trim says that the pcm is adding fuel and a - means it is subtracting fuel. 99saleens281 be careful who you listen to on here as i have read this complete post and most of these guys don't know as much as it looks like. to everyone else if you really know what you are doing then you shouldn't be offended. i am a ford senior master tech and a expert in drivabilty and i see this type stuff in the dealer every day, and i 99% of the time fix their cars with one part, the bad part not by replacing everything until i fix it. i have 42#ers in my 5.0 ranger with a 90mm maf and absolutly no drivabilty problems. the pcm is very smart in ways and also very stupid in other ways. aslong as you give it the input that it wants to see for the situation that is hapening then it will run like factory. plus my cam has 544 lift and 228 int and 238 exh at .050 yes it cams hard but no drivablity problems from the cam so i say B.S. to most of the post on this fourm. most anyone can tune for max power at wot but the real tunners make max safe power and also tune for the everyday drivablity. so 98saleen i will not reply to this thread again so if you want my advise then e-mail me. Tim
I don't think people are offended with your posts in this thread and everyone would also certainly welcome a "master tech and expert" in this forum. However, you shouldn't come into the thread mandating you being a one hit wonder because it reflects poorly on you. May be what you do not know about Mikes car is that he had wired a fan switch to ground to the eec wire and coincidentally had fuel pump surging issues at part throttle when the high speed fan switch was not engaged. Last I knew anyway. As a master tech I am sure you would agree that it could raise hell with the computer fuel trims chasing fuel pressure variations of 20 psi or more at part throttle. As far as I am concerned it is all speculation and irelevant until that issue is remedied. I am not a huge fan of C&L meters in higher hp applications but find it premature to blame the meter when you have other issues staring you in the face.

Shawn

Last edited by onerichrunner; 07-12-2002 at 03:58 AM.
post #31 of 69 Old 07-12-2002, 06:36 AM
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Chris Yates,

I do not disconnect the battery anymore for my KAM purges I do it in diffferently.
Believe me that the first thing I did before I fixed anything was purge the KAM only to watch it step its way back up to 25%. At idle it only took around 20 secs to go from 0 to 25% LT trim.

Winston.
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post #32 of 69 Old 07-12-2002, 09:05 AM
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Originally posted by onerichrunner


I don't think people are offended with your posts in this thread and everyone would also certainly welcome a "master tech and expert" in this forum. However, you shouldn't come into the thread mandating you being a one hit wonder because it reflects poorly on you. May be what you do not know about Mikes car is that he had wired a fan switch to ground to the eec wire and coincidentally had fuel pump surging issues at part throttle when the high speed fan switch was not engaged. Last I knew anyway. As a master tech I am sure you would agree that it could raise hell with the computer fuel trims chasing fuel pressure variations of 20 psi or more at part throttle. As far as I am concerned it is all speculation and irelevant until that issue is remedied. I am not a huge fan of C&L meters in higher hp applications but find it premature to blame the meter when you have other issues staring you in the face.

Shawn
Well put! What's up Shawn? Here are my thoughts directed at no one in particular:

1. No one claimed to be an expert. Well, except for the "expert master tech" who popped in for one post. I would hope that we are all here to learn from one another. For that to be the case, sometimes we learn, sometimes we teach, and other times we should just STFU and stay out of it (obviously ME included).

2. FACT: I've seen at least 4 or 5 cars lately with F'ed up LTFTs from installation of a C&L meter (my old Bullitt included). Some of them were throwing P0171, P0174 "System too Lean - Bank No. X" codes, others were not but all of them had idle LTFTs that were either saturated at 25% or damned close and the fuel trims in other cells anywhere from 25% rich to 10% rich.

3. I missed the fan switch mod in the original post, doh! However, if it were my car, I'd take a step back and review ALL mods that I made to debug the cause of the fuel pressure/fuel trim symptoms.

4. If the PCM was chasing fuel pressure fluctuations while in closed-loop operation, I would imagine that the LTFTs would not be affected by any substatial amount in one specific direction (i.e. biased toward enrichment) since they are the "average" or integration of the STFTs. I *would* expect the STFTs to be all over the place though. Do I understand correctly?

Cheers,

Mark

Last edited by mjchip; 07-12-2002 at 09:08 AM.
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post #33 of 69 Old 07-12-2002, 10:08 AM
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Wow, a real good thread!!!

mjchip, I see what you meant about cross section now. The C'L has those swappable sample tubes for calibration.

Yes, and eec-tuner can be used to limit the amount of trim, but the correct fix is to dial in the MAF function so the trims stay in a reasonable range.

Almost all drivability issues are MAF related. You swap the MAF, and it doesn't match the EEC any more. No company can provide a perfect maf calibation sheet because the intake ducting plays a big role there. Luckily the EEC can correct up to 25% (stock) so it's not usually an issue. If it is you have to modify either the MAF signal or fix the transfer function.

David

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post #34 of 69 Old 07-12-2002, 12:26 PM
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Mj-
My "master tech" post was directed one way. You, Chris Yates, and all with input is always well recieved from this corner.
I certainly am not an eec genious or "master expert" or whatever but do try to keep things as simple as possible especially when troubleshooting anything mechanical as well as electrical or electronic (eec). That is why I want Mike to take care of the "known" existing problem before tackling anything else. Like I mentioned in the above post, I am not a huge fan with C&L's in supercharged applications in particular but for simplicitys sake would want to see the fueling issue addressed first.

Mike- You never had that fueling problem until the KB BAP..??...Is that correct?
post #35 of 69 Old 07-12-2002, 12:39 PM
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Mj-
My "master tech" post was directed one way. You, Chris Yates, and all with input is always well recieved from this corner.
I certainly am not an eec genious or "master expert" or whatever but do try to keep things as simple as possible especially when troubleshooting anything mechanical as well as electrical or electronic (eec). That is why I want Mike to take care of the "known" existing problem before tackling anything else. Like I mentioned in the above post, I am not a huge fan with C&L's in supercharged applications in particular but for simplicitys sake would want to see the fueling issue addressed first.

Mike- You never had that fueling problem until the KB BAP..??...Is that correct?
Hey Shawn,

I understand how your post was directed and I too appreciate your input. I also thought that you hit the nail on the head so to speak. Even though your post was not directed at me, I AM NO EXPERT nonetheless, not even close. I'm just a guy who tries to keep an open mind and learn as much as possible from all sources. As others have pointed out, there is a lot of misinformation on message boards and the challenge is filtering valid information from the incorrect data provided by usually well intentioned but misinformed folks (this includes me from time to time).

When I debug problems in my day job or my night job, Zone-5 stuff, I try to be as methodical as possible. Maybe I was a little overzealous in claiming that the C&L was the culprit for the fuel trim issue BUT I still think that it is VERY possibly the cause. Whether or not it is related to the fuel pressure fluctuation problem is TBD by someone who has more information and possibly even access to the car (i.e. yourself). I really have no other input to offer than what I already posted.

Anyway, hope all is well and when you get break in the action, give me a call. I'd love to chat some more!

Thanks and take care buddy,

Mark Chiappetta

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