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What issues would my car have without a tune

2K views 31 replies 8 participants last post by  BKKSW 
#1 ·
On my 03 Mach 1 I’m starting to think maybe my issues are because the car needs a tune. Some times it feels and smells like it’s getting to much gas, or other times it is running great then just bogs down and starts popping, also sometimes feels like it’s not getting enough fuel.

I’ve checked for leaks, I’ve checked all the hoses, checked the plugs, made sure the gap was correct.

So what would issues be if things have been done to the car and never got a tune.

I was thinking it’s either needs a tune or a fuel pump.

Regardless if it’s the pump I still would like to get a Dyno tune. So I’m calling tomorrow to a few shops that do that. Plus I would like to know if the cars going on full power if not I’m guessing it would tell me that there is a problem if it only pulls 200hp.
 
#2 ·
If it is stock and acting up, you don't need a tune. You need to find the issue and resolve. Are you getting any codes? Have you cleaned the MAF? How old are the O2s?

Throwing it on a dyno before it runs as it should would be a waste of money as you will be spending valuable dyno time trying to figure out why it won't run right.
 
#5 ·
I don’t know what’s all done to it. I’ve checked lines, looked for leaks, plugs and stuff like that.

It has no O2 sensors. Original owner took them out. It has off road x pipe, no cats, magnaflow mufflers also has kn air filter. That’s what I can 100% confirm.

Was told it has 373 gears. Was told it has a bama internal chip.

Also yes I did clean the maf. I had codes ran about 2 weeks ago. One came back as a sensor right by the maf and the maf itself. When I changed the sensor I noticed the maf was completely unhooked. I cleaned it and reconnected it. I did all this with the battery unhooked.

The reason I said either a tune or fuel pump is sometimes feels like it’s getting to much fuel and sometimes not enough and bogs down.

Reason I was asking about the tune was I didnt know if the little things that were done to the car would effect the computer.


I talked to a performance shop and they told me he could dyno it but wouldn’t recommend me getting a tune with them because they charge 600 for the tune and 399 for the sct tuner. So 1000 and he said all they do is use the tuner and write a tune for it and it would be cheaper for me to get the tuner an a custom tune.

So is that how dyno and tunes are all done, or is that just the way that shop does it.
 
#6 ·
Thats just the way that shop does it. I charge a set rate of $550 to dyno tune cars here at my shop in new orleans. It costs me $60 for a chip on the older cars 1983-1995 and nothing to direct flash the 1996 and newer cars. I chalk up the $60 as being a minor expense. Oddly enough 90% of the remote/online tunes I do is on older vehicles and 90% of the shop work I do is newer vehicles so the costs cancel out on my end.

Getting back to it you have some major problems.

First a vehicle cannot be properly tuned without o2 sensors. Put new ones in immediately and they are required before you can tune it.

If the maf was unplugged when you got it then chances are something is wrong with it. With no correctly functioning maf and no o2s that engine could very well run like crap.

The sensor right by the maf is the inlet air temp sensor which is a global fuel multiplier. That sensor being disconnected could case fueling issues as well.

You need to unfuk what the previous owners have done. First thing first remove that chip it should be obvious if you have a rear end gear change since the speedo will then be off.

Get the o2s installed, chip removed, pull codes and go from there.
 
#12 ·
Stock O2s are fine. You need to put some catalytic converters back in or ditch that mid pipe for a stock one otherwise, you will throw codes once you pull the chip out. Check up high on the mid pipe to see if you are actually missing the upstream O2s. If you are, it is not surprising the car runs like poo.
 
#13 ·
The car has no chip, I took the panel off and gently pulled the wires until I got to it and it looked normal like one I found on google images.

So that means there are no 373 gears either.

How many o2 sensors are on the car I only thought it was 2, I’m guessing 4.
 
#15 ·
There's another way to look at this. It may require more work in the beginning, but save you more time and money in the long run.

You don't necessarily need to return the car to ground zero, unless ground zero is where you want the car to be. If you had plans for this car you haven't otherwise stated it may be possible to skip some steps getting there by learning where you are and mapping out how to get to where you want to be.. if that makes sense?
 
#16 ·
Eventually I want to rebuild the engine with forged internals, different cams, supercharger, I want to get the heads with the More threads, want to get head work and intake work done, long tube headers and want to get the body repainted and fixed. It’s my 5 year plan, hoping to have it done long before then but had to sell the wife on all the work some way.
 
#17 ·
Without MAF and/or O2 sensors hooked up, the computer has no idea how much air is coming in or how much fuel is being mixed. So, it's running in "limp" mode with a rich fuel mixture and I'd imagine retarded timing. If I looked at a car and the MAF was not connected, or it had no O2s, I'd already be done looking.
 
#20 ·
I didn’t know the o2 sensors meant that much, I had a 95 an took them out and it was fine. But I’m learning with the 4v and appreciate all the stuff you guys are telling me.

As for the maf unhooked I’m pretty sure it was the shop that I took it too, to have the head fixed. Just never hooked it back up, because when I bought the car it was hooked up. Either they unhooked it for some reason or it wasn’t connected properly and came undone.
 
#18 ·
It comes from the factory with 2 upstream and 2 downstream O2s. The upstreams monitor the A/F ratio and adjusts trims accordingly. The downstreams monitor the catalytic efficiency. They basically look for a voltage variance from the upstream O2s to determine is there is a catalytic converter present and functioning. You can have the downstream O2s turned off in most tunes without impact to performance.
 
#21 ·
Your car can't go into closed loop without O2 sensors. Same thing for the 95. Without O2s, it can't make corrections. So, if it runs rich, there's no way for the computer to know that in order to compensate.

The MAF provides communicates load, and without it, the computer reverts to base tables in either alpha-n or speed-density (not sure MAF cars even have a MAP sensor for this). Those tables are "limp mode," and they effectively pull timing (maybe) and add fuel (definitely) in order to protect the engine. Result? Lots of unburned fuel making it into the exhaust. Not sure about the Mach 1, but modern cars have wide band O2s, whereas the 95 had narrow band O2s and less adjustment in the tables.
 
#24 ·
Indy, It's possible, I suppose, but unlikely. Unless there are chips I'm unaware of, "Bama" does mail order tunes only, which they'll update generally based on part installations, but not on the dyno and not truly custom to your vehicle. Not the kind of place that's going to put a street car in open loop. He'd be better off ripping that crap out of there and going back to stock, in my opinion.
 
#25 ·
Yeah, Scott. As long as you're sure that your speed and RPM are accurate. Your car is probably better, but the old foxes that I'm familiar with are notoriously inaccurate. Also, if you swapped gears, it's possible that your speedometer might be off. Use GPS. Google speed gear calculator or give me your info and I'll put it in an excel calculator I made. Need your tire size, trans gear ratio (which I probably already have if you tell me what gear you're in), speed, and your RPM.

Alternatively, jack up the rear (remember jack stands), get under your car. Mark the driveshaft. Mark your wheel/tire. Watch the driveshaft. Spin your tires 10 rotations. Count the number of times the driveshaft turned, and divide the # of driveshaft turns by 10.
 
#27 ·
To determine the gear ratio, you need a little math. First, get the revs per mile of your tire (Calculator).

Then, run the car in a 1:1 gear (4th Manual, 3rd Auto, turn off OD to hold 3rd) at 60MPH and record RPM. I would get speed from a GPS app; the speedometer may not have been corrected for the rear gear (if it isn't stock). Note: By doing 60 in a 1:1 gear you remove most of the math involved. I can provide the full equation if you want.

You can then divide engine RPM by the tire revs per mile to get the gear ratio.

Example: If 60MPH in 4th = 2900 RPM and you're running 245/27/15s (786 revs per mile) 2900 / 786 = 3.69, which is a 3.73 gear. It'll be off a hair due to the fact that you're reading an analog gauge, round to the nearest available gear ratio (3.27, 3.55, 3.73, 4.10 and so on).
 
#28 ·
Rear gear = RPM * pi * [(tire width * aspect ratio/1270) + wheel diameter] / (1056 * trans gear * Velocity)
Tire width and aspect ratio are the first two numbers on the side of your tire and wheel diameter is the 3rd. i.e. 245/45/17

Or provide the data and I'll let the excel do the work.

or just use an online calculator...
 
#29 ·
eBay has a set of o2 sensors for 50 dollars for all 4. I don’t even know if they have a brand name, I spent more on the ones I bought, but they haven’t shipped yet. Does it matter as long as they fit, or should I stay away from those eBay China made ones.
 
#30 ·
No experience, as I always go with known good brands. In the past, when I've gone with the cheap brands, I've ended up regretting how unreliable a collection of cheap parts has made my car. Haven't done that since the early '00s. I'll always end up with OEM or Bosch on O2 sensors. Or, perhaps on a rare occasion when multiple sources agree, I'll take a recommendation from the forums.
 
#31 ·
Sorry been really busy with grad school and grading papers for the end of the semester.

But last night I finally put the O2 sensors in, and the check engine light is finally gone. Car doesn’t pop and runs really smooth.

I also changed the c&l cold air intake to a jtl. Not really sure if it it was worth the money or not.

Noticed while changing the set up my MAF was aluminum and not plastic like the stock one. I couldn’t find a name on it or a part number so I’m a little confused.

Also with the o2 sensors are they all the same. Because when I got the NGK ones they were all the same and boxes had no part numbers or anything. Only difference is 2 of them had about a 1/4 inch longer wire.

I’m happy it’s running better but now I noticed other issues lol. That’s the game, fix something and something else is more visible.
 
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