My buddy has a 97 TA with LE2 setup, OBD I conversion and all the bolt on's.

He hasn't driven the car much at all in the past year, and now that he is driving it again its starting to act up.

The short term fuel trim cells are going through the roof at idle, then the car has a bad miss, till it cleans out. They start at 128 then they clime to 185 at 190 the car starts acting up then at 200 the car starts bucking and wont respond to the Throttle .

I took a 20 minute log in Datamaster i can post up, in Data, or export to Excell, if any one wants to look at it.

It didnt have this problem before, not sure what has changed, we did change the ICM out with a new gm one and did the same thing. Maybe the O2's are out , not positive, they seam to still be reading ok.

I have read that on big cam's with alot of overlap, the pcm thinks their is a lean condition from the fresh air passing through the chamber out the exhaust valve to the o2 sensor. The pcm tries to compensate by adding fuel when really it doesnt need too. On my solid roller , Moe programmed the pcm to stay in open loop for this reason.

Thanks for any help, let me know if i need to post the tune or the data log


Brady

 

Post it up, i'll take a peep at the log. What sort of exhaust setup does it have on it. Do the plug wires have any burns and are they secured properly. I would think it would either be a misfire, or an exhaust leak. Also blms should not climb higher than 160 max unless you guys changed something in the tune. It also might have a clogged injector unless its doing this on both sides? How does it act under open loop conditions like cold start. How are the trims looking on the highway at cruise.

 

I sent it to your registered email address.


Pace long tubes, y-pipe, open cut out, durring logs, with a flow master and tipps.
Plug wires are msd, pretty sure no burns, he changed the plugs after it started acting up, thinking that was the problem.
Also change the header gaskets on both sides, it did have an exhaust leak, all fixed now.
The long terms dont go past 160 but the shorts do all the way to 200!
We haven't messed with the tune much , it was a mail order from PCMforless, but its old and i doubt we can get a free retune 3 years later.
Not sure on open loop conditions it was a hot day and the car was already warmed up , so it didn't stay in open loop long. It acted up toward the end of the log and i had him kill the car and start it back up and it still had problems, and the Short terms were lower then.
Cruzing around its fine, just at idle , at a traffic light it acts like it is loading up on fuel , its spits and stumbles and runs very , very poor.


One small detail i left out because i know as soon as i say this everyone will say this is the problem and i dont think it is. The car just rolled 100K on the stock opti, lol..

WOT is good, drive ability is great, just at long idle conditions it start to act up when the Short Fuel Trim cells clime above 185

 

Your friend has more problems that at idle Brady, most of his fuel trims are up near 160. I am guessing this car has stock injectors from the looks of the base pw time (looks good for 24lb inj), which makes me think maybe it also has a stock fuel pump and probably regulator. I would check the fuel pressure at the valve on the rail and make sure it was in the 40is range. If its below that it could be a few things, the pump the filter or the reg. My advice is to start easy/cheap and get more complex. You might also check the fuel lines etc and make sure nothing is kinked or has a hole in it.

My take is that your fuel psi is not adaquite, and because of that at idle you're getting really poor fueling and atomization. Basicly fuel is dribbling out of the injector with the short open time it has to supply fuel in. This will lead to poor combustion from poor atomization. The net result is rich places immediately around the large droplets or puddles which makes it smell rich and loaded up. It also leads to lean plockets in the chamber which makes it burn your throat and gives you a nasty little soup out of the exhaust. Its probably just as bad while cruising but you dont notice it because you cant stand behind the car and smell it, and also the temps are higher on the piston and the globs of fuel evaporate more readily at those cyl temps, plus the number of cycles has increased and problems like that are less noticeable at higher rpm. I would not drive the car hard or really at all until i found out why it was having such a hard time supplying fuel.

If thats not it, your o2 sensors are junk or you have some badass exhaust leaks.

Report back here what you find. Also make sure the cutout is shut for testing at idle after you fix whats wrong. Make it harder for air to come up the pipe just to eliminate that. I can give you a couple of suggestions on the tune but i'd like to see what it does after the issue is resolved before i say anything.

Best of luck.

 

Walbro 255 in tank, Ford 30 lb red top injectors. I checked the fuel pressure it was 42, at idle no vacume, so i swapped out the FPR with another stock unit and now its at 44 psi at idle no vacume.

We didn't stand behind the car to see if it smelled like it was loading up on fuel, thats just what i was guessing from looking at the data.

O2's are old, but like i said, he had a horrible exhaust leak on both sides, so we replaced the header gaskets, no leaks at all now.

The tune is programmed for 31.65 IFR

 

Hey I took another look at it, your iac may be reading a high unless this was one hell of a hot day you logged on. It shows your idle air temp being in the 105-140*F range. If it was really 70*f out that day that would throw the maf calibration off quite a lot. A good test for that is to see if it agress with the coolant temp reported by the cpu.

Also you might check the hose from the maf to the tb, but your idle readings for maf look ok if not just a hair low but its an m6 so it wont use as much air to idle with.

Your o2 sensors are switching correctly everywhere except idle, we'll worry about that later, right now your biggest problem is your cpu is adding as much fuel as it possibly can everywhere. tps is also a little high for my taste but no enough to trip a code, I like to see them set about 0.67 but it shouldnt be a problem.

I'd like to take a look at the flash you guys are running if you have the tools to pull it off the pcm and email it to me.

 

I took a look at the tune this morning, dont see anything wrong there. I think you either have some sort of electrical or mechanical failure. You said it has fuel pressure so that either leaves a miscalculation of airflow by the computer or a problem actually supplying the fuel. Try trading out the idle air temp sensor and see if that helps the trims unless it really was over 100 that day. Another test you could do is unhook the maf and run it in speed density to see if its any better to eliminate the maf as a problem.

 

I swapped out the IAT sensor with mine and it was 89* that day but his car is a 97 WS6, so i think its pulling a lot of engine bay heat through the air filter.

We are going to try a cold start in open loop and see if maybe its the O2's

 

I am also running rich at idle (and a bit of a high idle) but haven't yet done a full data log - that should happen on Monday. I am interested to see how your situation works out.

Bryan at PCMforless (who did my tune) suspects it may be the combination of IAC and TPS in conjunction with my new 58mm TB. Have you checked out those elements?

Good luck.