Sometimes dies when slowing down.. - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 66 Old 06-14-2019, 12:03 AM Thread Starter
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Sometimes dies when slowing down..

This is a long running problem and I think there are two other threads I've started and got no where with 2 and 3 years ago. But I really would appreciate any suggestion you think may help.

Not all the time, but lets say 3-5% of the time, if I'm accelerating as you would from a normal stoplight speed, and then let off the gas, or even if going roughly 40mph you just let off the gas, the rpms drop and bounce around 600/500/400/300 until dies. Not fun having 305's with no power steering and brakes while in traffic.

Normal operation happens the rest of the time, in that the RPM's slowly fall to 1000/11000 and then more slowly fall to 800/850 as the final idle speed.

So far I've checked all the vacuum lines, ran a smoke test looking for vacuum leas, checked grounds and all connections, and replaced the idle speed motor and the EGR valve. It used to do it more, but changing the EGR valve helped it not happen as often.

Anyone have any ideas?


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post #2 of 66 Old 06-14-2019, 11:42 PM
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needs more dashpot simply fix it in the tune

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post #3 of 66 Old 06-15-2019, 09:29 AM
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you never posted results of the data you logged 3 years ago.

that is why those threads never went anywhere

you keep saying you have looked for air leaks, and bad electrical connections, but never mention what is actually happening that the ecm is seeing.

with data streaming, you dont even have to lift the hood to get direction

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #4 of 66 Old 06-15-2019, 09:48 PM Thread Starter
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Our tuner added more in the tune and it didn't change. He also went through the data stream and didn't find anything but I'll catch it again and post it.

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post #5 of 66 Old 06-15-2019, 10:03 PM Thread Starter
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I have two other thoughts, one I think you debunked a few years ago. The first one is this started right about the time I found a BBK 62mm twin throttle body and added it. Would the difference between a factory or BKK gasket or the TB itself cause this, assuming the TB is defective somehow? And the next thing is I relocated my battery to the trunk and only ran a positive to the trunk, and connected a negative to the interior metal of the trunk. Our tuner had some issues with something, I think flashing the ECU, and he claimed he's seen the same issues when a ground wasn't run all the way back. He claimed the thing metal of the body couldn't carry the same current a proper cable could.. I did measure resistence using a megger I borrowed and the body did exhibit more resistance.

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post #6 of 66 Old 06-16-2019, 12:50 AM
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your tuner must have tuned for a different TB

if you think you have a voltage drop, load the body with current and measure for it.

Your tuner added more of what in the tune?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #7 of 66 Old 06-17-2019, 02:04 PM Thread Starter
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I went to my storage and found my SCT x4. It has my original tune and my other tunes. I ran it through the updater on my PC and it said running the updater will erase 'your original tune." Does anyone know for sure what is erased if anything? And is the update feature on the SCT itself undfer the settings tag the same thing or different?

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post #8 of 66 Old 06-22-2019, 05:43 PM Thread Starter
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I am absolutely new to doing anything with my x4 other than changing tunes. I think I've saved the datalog properly though I can't make out much from it looking in the Link software. I attached the file.

I've long suspected the BKK 62mm TB so I changed back to the stock Ford TB (I know I'll need to get my tune updated to reflect this) and a new Ford TPS I had.. and the car ran better than ever. The idle reacted like it should. You take your foot off the gas and the RPM's drop to 1100-1200 and over the next 15-20s slowly drops to 800. With the other TB almost every stop the rpm's would drop to 600-500-600-400-300-800 or in other words they'd be all over the place. Now it's not. Though, when I first brought it out of the garage after the TB change the RPM's dropped down to o400-600 that one time, and then worked perfectly for about 20 minutes with maybe 100 cycles between 0-30/40mph-0 All perfect except for one instance where it dropped and died like it did before. The first time out of the garage I attributed to the computer re-learning.. possible? But the second time? I drove for another 5-7m after the last drop and everything was fine.

Any help would be greatly appreciated. I've been afraid to drive my car during hours of traffic for several years now, wasted hundreds at the Ford dealer, and not really enjoyed the car like i should. Thank you.

Apparently I can't directly attach this file.. so I put it on one of my servers. Just use this as the URL and you can then download and save it. http://bangkokimages.com/log.csv

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post #9 of 66 Old 06-22-2019, 07:52 PM
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did you disconnect the battery when you threw parts at it?

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post #10 of 66 Old 06-22-2019, 08:40 PM Thread Starter
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No. I know better and just forgot to do it. I'll go flip the switch and let it simmer for a hour or so and then try again.


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post #11 of 66 Old 06-22-2019, 09:48 PM
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that is not why i am asking

you are jumping ahead of this systematic process, this leads to misdiagnosis.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #12 of 66 Old 06-23-2019, 02:41 AM Thread Starter
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Understood and I'll refrain from doing so again.

Changing back the TB while not part of this logical process, was part of a process I've been running in the back of my mind for a while and I was hoping to rule out the TB before starting this new process of collecting a datalog.

I bought the BKK used and from a guy who in retrospect I didn't feel good about. His reasoning for selling. At the time I made a mental note and didn't install it or piece together the correlation for nearly a year. Throughout my ownership of this car I've often taken assignments overseas for months to years at a time so keeping the pieces of information in order can be a chore at times. And by the time my suspicions grew my stock TB became lost. I found it while looking for the x4 and thought I'd swap it out and take it out of the equation and record a log on my test ride just in case..

And the car ran much better. Before the rpm's would waver but most of the time not die, but occasionally it would. With the stock TB, gasket, and a new TPS (bought to fix my 2002 5.4l FX4 Crewcab)I had waiting to go into another repair but put it in to rule it out. Anyway, the rpm wavering has stopped. It works like it should other than when pulling out of my drivie where it wavered and didn't die, and the one time it died in thie last few minutes of the log.

l've got the battery disconnected with the neg shorted to ground, and will connect and repeat the test tomorrow. Maybe I'll get lucky.

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post #13 of 66 Old 06-23-2019, 09:29 AM
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I think you will understand a little better if you know

Idle is learned over run time, and a number of starts

When you erase the Kam, you erase the learned corrections

When you changed TB, you most likely changed how much air if flows when closed

you would have seen this while logging idle short and long corrections

are you able to log corrections?

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post #14 of 66 Old 06-23-2019, 09:36 AM
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i looked at your CSV, can you get one with the stalling?

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post #15 of 66 Old 06-23-2019, 04:18 PM Thread Starter
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That was the one with the stalling. Once in the first maybe 20% and another int he last 10% of the file.

I don't understand what logging corrections means. Is there a link where I can learn more about how to use these files with my software?

I left the battery disconnected all night and this afternoon when I started it, the idle quickly stabilized and I drove for about an hour with zero issues. Actually the idle has stopped surging and the car is running great. I stopped and erased that log and started a new one to keep the size manageable and soon after when I stopped the idle fell down to 400-450 and then corrected. I noticed at the time, when I had my foot on the brake I was also rolling the window up to turn on the A/C. I drove around again and about 5m later turned the A/?C on while braking, and it again dropped down to 400-450 before correcting. Is this the ECU learning to handle increased electrical load? I attached the new log file, one more in a link: http://bangkokimages.com/log1.csv

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post #16 of 66 Old 06-23-2019, 06:44 PM
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there isn't anything that suggests the engine is running in that first log

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post #17 of 66 Old 06-23-2019, 07:04 PM
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so i graphed the last log

do you blip the throttle when rpms are dropping?

I can see it in the log just as rpms lose control to a stall

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #18 of 66 Old 06-23-2019, 08:15 PM Thread Starter
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That's strange, no idea why it wasn't showing a running engine.

Second graph: I don't blip the throttle. I just let off the throttle and move my foot to the brake.

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post #19 of 66 Old 06-23-2019, 11:02 PM
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are you able to graph it?

it is easier to see things

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #20 of 66 Old 06-24-2019, 08:29 PM
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?

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post #21 of 66 Old 06-24-2019, 09:54 PM Thread Starter
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The first graph that didn't show a running engine was: http://bangkokimages.com/log.csv and then the second graph where you said you could see the blip is here: http://bangkokimages.com/log1.csv I'm trying to keep them sequential but I could have numbered then better.

Do you need me to capture another log?

Thank you.

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post #22 of 66 Old 06-25-2019, 08:53 AM
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I have graphed the second log

I want to point out the stalling on it, and what i see

are you able to graph it, and follow along?

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post #23 of 66 Old 06-25-2019, 09:41 PM Thread Starter
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By graph it you mean bring up the file in LiveLink Gen II and find the RPM low points? Yes. I'm not familiar with the interface yet but I'll can try picking it up as we go.

Really curious what you found.

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post #24 of 66 Old 06-25-2019, 11:55 PM
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yes, a graphical display of the data

each PID as a function of time

so you can see what the ecm is commanding at each point in time

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post #25 of 66 Old 06-26-2019, 01:17 AM Thread Starter
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Isolating the RPM on the graph I see two low points in RPM, both at 400rpm at 6:50 and 12:10.. The coolant temp is a flat at 180, vehicle speed looks pretty much correct, both fuel, 1&2 and short/long trims follow, I'm not understanding the "desired idle rpm", everything seems at it should except Engine load?

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post #26 of 66 Old 06-26-2019, 09:01 AM
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desired idle rpm, is just a target rpm, it changes depending on conditions

graph

spark
rpm
idle speed valve duty cycle
throttle position


spark is used for idle rpm
speed valve makes gross air changes for decel cruise and loads

look closely how spark and speed valve react during transition into idle

during stalling and non stalling points

tell me what you think?

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post #27 of 66 Old 06-26-2019, 06:23 PM Thread Starter
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First, as I decrease the resolution of the graph I can see that the idle speed dropped to roughly 300rpm @6:45 and 6:48 and then again 400 at 12:03 and 500 at 12:06.. so it's not one straight fall in idle, but like a fall/rise fall in a 3s period. Not sure if that means anything.

It appears as the throttle is lifted rpm falls, advance increases, and the speed valve at first falls and then it rises again for a short period at the 12:03/12:06 period before smoothing out with a few oscillations. During the 6:45/6:48 period the spark is oscillating more than it was a the 12:03/12:06 set, while the speed valve is falling more.

About the spark and speed valve association.. between the two sets they're very different. If you look at the fall of the throttle position on both it's straight down and then horizontal for right at 10-12s, while the spark increases and the speed valve decreases.. wiht the bigger differences being the amplitude and variations of the speed valve and spark.. guessing it looks like the speed valve is wonky and the feedback it gives causes the spark to fall which the rpm follows. The Idle Air Control Motor (CX1654) was the first thing I looked at when this started thinking I needed to clean it out. When it looks pretty clean I thought the motor itself might be at issue so I changed it.

Am I way off in left field somewhere?

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post #28 of 66 Old 06-26-2019, 06:43 PM
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you are getting the hang of it

have you compared what is happening during the stall compared where it returns to steady idle without stalling?

another thing is spark is wacked

it goes to 9 deg out of no where

are you able to log idle state flags?

there is a reason for the low spark, speed valve seems a little low, like the throttle is open too much.......

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post #29 of 66 Old 06-26-2019, 07:01 PM Thread Starter
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Flags = Bookmarks? I can place and move between bookmarks.

At the moment of recover the speed valve is now rising. And when it rises it's smooth. When it falls it's jagged like it's sticking. Does this sound right? Isn't the speed valve designed to react to the RPM? React and keep it in the desired ballpark. And the speed valve gets it's marching orders from what, the timing? Or more accurately from the ECU which is reacting to the timing? Or does the speed valve work right off the idle signal?

Looking at the timing and speed valve and other signals.. are they supposed to be so jagged? What is that a function of, time or is something interfering? I'm curious if the ground I've been thinking about is allowing something to make the signals like this?

Everything is fine until something happens. So a timing curve or setting isn't the issue. It would have to be something interfering and reacting when tolerances are exceeded, or something is worn or broken like the speed valve.

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post #30 of 66 Old 06-26-2019, 08:11 PM
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flags

I mean actual PIDs to log

there are 4 strategies for idle, depending on state

i would like to know what idle strategy is using coming out of part throttle

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post #31 of 66 Old 06-26-2019, 08:13 PM
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the jagged is from sample rate, when you log

zoom out it will be smooth

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post #32 of 66 Old 06-26-2019, 11:53 PM Thread Starter
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What is PID?

How would I find the idle strategy?

After dinner I pulled off the speed valve and its as clean as when I put it on. But looking it over carefully there are no manufacturer marks on it. Motorcraft parts normally have their marks. With all the counterfeiting and since I got it off ebay it makes me wonder..

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post #33 of 66 Old 06-27-2019, 09:27 AM
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pids are those items you logged over time

ie, spark, tp, fuel trims...........etc

is there a list of pids you can log?

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post #34 of 66 Old 06-27-2019, 04:35 PM Thread Starter
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Yes. I attached an image file of them.
Attached Images
File Type: jpg PIDS.jpg (60.6 KB, 7 views)

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post #35 of 66 Old 06-27-2019, 07:56 PM
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is that all of them?

we need the throttle flags

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