Hesitation on Acceleration and Stalling Idle

[Jon89le]

For the past year or two i have been having idle issues with my 3.1 as well as delayed acceleration. Sometimes when i accelerate slowly, it feels as if the car is choking. I'll stay at a consistent throttle and the car will accelerate faster or slower. The idle issue is even worse. Now, this does NOT happen all the time. Whenever there is a load on the motor the idle will become rough and at times stall. As soon as i put the car in park or neutral, idle stabalizes right out.

 

Today however the both issues have become worse. Accelerating the car feels like its choking and wants to stall until i pretty much am cruising in second gear. At idle, well, there is none. Engine idles very low and rough, then will shut off. When my ECM went i had a similar problem but when it would shut off, i couldnt start the car until it cooled down and once started, it would shut off as soon as it went into open loop like clock work. I should also note that today, this roughness was felt even w/o the tranny engaged. Became rough around 2k rpm.

 

The motor has been rebuilt; cam, pistons, heads, etc. and has a FFP chip. Like i said, the ECM was replaced about 2 summers ago. IAC and TPS were done this past summer. The TPS was replaced 3x since the first two were defective (what are the chances). Anyone have any idea what the issue is? Im almost sure that both issues are related. I have checked all my vacuum lines already. It almost feels like my spark is cutting in and out on the acceleration and the timing being incorrect at idle. The ICM was around the same time as the ECM. Any help is REALLY appreciated. I have a 3hr drive home for Thanksgiving through the Jersey Turnpike and for those who have been on it, there are spots that if you get stuck, you're up shits creek w/o a paddle.

[19Cutlass94]

You can try some stuff like a fuel filter or the coils. Also, if you have a cat. check that because it may be clogged. I was gonna say maybe look at plugs or something that would indicate you have lost a cylinder, but if it idles smooth in park or neutral, that kinda throws that out the window.

 

It may very well even be your tranny?

[Jon89le]

Forgot that one, when the ICM went i replaced the filter and the cat is brand new. Just did my custom exhaust this summer. Coils is a possibility. I will have to ohm them out once I go home. Or rather, if I make it home.

[lakefxgp96]

I want to say its possibly the MAP. Sounds like a fueling issue to me. Cant completely rule out a bad coil or an ICM yet though

 

First question I have is do you have an SES light either now, or ever?

 

Assuming you do not have an SES light, it lowers the chance that its the MAP or the TPS and increses the chance that its a bad coil, fuel injectors, fuel filter, bad coil, ICM...something to do with a misfire.

 

Now here is the real kicker, how certain are you that the cam is correctly timed? has it been like this exactly since the rebuild?

 

i couldnt start the car until it cooled down and once started

 

Because that is PRECISELY what overly advanced timing will do to you.

[Jon89le]

Ban this guy!!

 

We cant physically control ignition timing but once i replaced my ECM that issue went away. When i first built the motor everything was fine. This only developed a year or two ago. I built the motor back in HS, early 2002. And of course there is no damn SES light. By the time an SES light comes on with these POS OBD1 cars, you're on your last breath. OBD2, damn bad gas triggers that sucker.

[lakefxgp96]

Yeah obd1 SES doesnt tell you anything unless a sensor breaks. they are more concered with your engine putting out the right amount of co/co2/no2 than a piston trying its hardest to put a valve back in the head.

 

the Cam can be timed incorrectly (like a tooth off for example)...and a common symptom of that is hard warm starts. I learned this the hard way on the DOHC, you get 4 cams to screw up any way you want!! lol.

 

My first impression was the TPS, but having been replaced a number of times, and no SES, then its probably not it. MAP probably not since there is no SES (not completely impossible though)

 

Im leaning toward coil pack, maybe even crank position sensor. god this is a tough one. If you had obd2, it would have been fixed 2 years ago

[Jon89le]

Hell, ill replace all of them. My machinist did my crank timing and set it straight up. But if that was an issue i'd have known about it right away. MAP was replaced at one point after the rebuild when my ECM went. My Service Manual said it was the MAP or ECM so i obviously tryed the cheaper of the two first.

[Jon89le]

Oh, and i did replace the Crank sensor. Im loosing track of everything..

[lakefxgp96]

yikes yer killing me!

 

coil pack(s) maybe? perhaps you had one set go bad and now another one did. but is it really feeling like a misfire? or is it just hesitation and sputtering?

[Jon89le]

I might end up taking a vid of this. It could be a coil, but I was under the impression that once a coil goes, it goes. With regard to the acceleration, it feels like it wants to shut off, like i need to fight the throttle to get it through 1st and that 2k rpm range. After first im never that low in the rpm band due to my Torque Convertor so it drives somewhat fine, but still with a slight roughness.

[lakefxgp96]

My grand am from way back when, a 92 2.3 SOHC, had a messed up coil. The car would hesitate, the Tach was out of wack and the car would fail to start when wam... The dealer i took it to (yeah i was dumb back then) replaced the computer, fuel pump, fuel injectors, and an ICM....they gave up and took it to another dealer who then replaced a coil and re-flashed the ECM because the other dealer used the wrong code...everything was fine after that!

[slick]

Injector's ohming out OK? I'd pick up a set of coil packs and try that. I'm sure you've checked your plugs and wires, that they are fine. Intake gaskets good? Fuel pressure regulator?

[Jon89le]

Yea, wires and plugs are fine. My meters are at home and im at school until thanksgiving. Gaskets seem fine but im not so sure its a vacuum issue since the problem isnt consistent.

[JoroCorona]

Sounds to me like you might actually have some transmission engagement problems. It almost sounds like the TQ isn't multiplying properly. Almost like the stator is stalled.

 

But go for the coils first. Could be the problem and is FAR cheaper then a TC.

[Jon89le]

What makes you say transmission?

[JoroCorona]

If the stator is caught in the locked position inside the Torque converter, the TC wont multiply the torque. No torque multiplication == weak off the line with idle problems until late 1st gear or early 2nd.

 

However, now that I've re-read your first post, if your still haveing idle problems without the transmission engaged. Nix that. Its the ICM and Coils. Goto the junkyard and get them off of a 3400.

[Pabz]

Coils! Two of mine went, i could still drive but major hesitation, probably icm went too!

[Jon89le]

But if the problem comes and goes, can that be a coil? Can a coil slowly go bad?

[lakefxgp96]

But if the problem comes and goes, can that be a coil? Can a coil slowly go bad?

 

Mine worked out that way.

[Pabz]

Take em off and check for cracks.

[Jon89le]

To check the ohms on the coils, is there a way do to it while they are on the car? And the range, is it 5000-8000?

[92 GP]

It sounds like a manifold pressure problem. Either a reading (bad MAP) or there's a leak somewhere

 

Things that could cause this - leaks, bad gasket (throttle body, EGR), missing EGR bolt (since it goes all the way through)

 

When i took my engine apart for a topend rebuild, i lost a bolt to the EGR. I said fuck it, and left it off. But when i went to take off, it did the EXACT same thing. Put it back on, then it ran smooth as hell. Check all your bolts for your manifolds, as well as gaskets before you go spend a shitload of cash. Otherwise i've got a spare brand new MAP you can have for a good price if you haven't gotten a new one

[92 GP]

also WILL cause stalling at idle

[Jon89le]

Well i finally got a break from work and looked the car over. Sprayed a few things down and theres no leaks. Anyone know if its possible to test a sensor while its off the car? There are a few sensors I could replace but I would like to know IF what im replacing is the culprit. Would the GM service manual have the correct readings (if its possible)? If so, I could just check mine out at home.

[Pabz]

Let me know which ones you are checking and i will send you a snapshot outa my gm manual. Its for the 2.8 but sensors should be the same no?