85f-bird

alright, has anyone had a problem with this, it's hard to explain so please bare with me. Alright, the issue comes with acceleration. When the pedal is placed slightly more than say eh....1/4-3/5's of the way down the car begins to hestitate and does so from roughly 2900-4500 rpm's. This doesn't happen if the vehicle is in neutral, only in the drive gears, and i haven't tested it in the reverse gear but I assume it'd be the same, but i'll test that just to make sure. So, the car does this only in gear, also, the idle is very speratic, and bounces around a lot, normally it settles at about 500rpm (probably need to bump that up) and the car has recently been dying while it's stopped. I had changed the MAF a couple days ago, and everything seemed worse, (the problems didn't exist until then) afterwards i swapped MAF's back, the problems slowed but were still there and the car didn't die nearly as much. I think that's about it, oh, that and a friend of mine hooked his OBDII Scan Tool up to my car and it came back saying the engine's running lean and that there was a problem with the EST, but i had the EST connection unplugged earlier that day, so the code might have still been in there. Since then i've cleared the code and the problems persist. Thanks in advance for any help, and ill be away for a little while over the weekend, so i might not be able to respond right away. Thanks again.

Nixon1

Ok...Yes, if you had the EST connected at all and had the car started during that time any time during the past 50 starts, it will show up. I assume the OBD-II scanner was using an OBD-I program in memory for reading your car right? Because our cars don't have OBD-II..I wish they did!! *** what a genius system. 500 rpms is way too low of an idle, so that could explain a lot of the rough idle and bouncing. Should be more around 750 I believe. How's all your ignition components? Plugs, wires, cap and rotor... How's your fuel filter? Clogged filter will cause starvation and stalling coming to a stop. Also, a sticky IAC valve will cause stalls coming to a stop as well. Btw...you said it's running lean? If that's correct, then it could be a bad fuel filter. And how is your O2 sensor? If the oxygen sensor is getting old, instead of throwing a check engine code as malfunctioning, the comp won't know it's acting up...the O2 sensor starts to give incorrect readings..usually the O2 sensor will indicate a false lean condition when it's failing, causing the computer to compensate by adding fuel, thus making you actually run rich. If you haven't replaced your O2 sensor recently, like within the past year or two, I would do it. For the $20, it's definitely worth a shot and can save you some money on gas if the old one is failing. I kind of led you in 500 directions there...but I was trying not to leave any possibilities out. Now, for the narrowing down!

Gumby

Time for a tune up, plugs,wire, cap rotor, even if you dont think its time. been there, tried everything else first, wasted time and money and a good tune up did the job.

CaliCamaroRS

Pull the fuel filter off and blow through the inlet side. You'll know if it's plugged.

Check the resistance of all plug wires. About 3,000-4,000 Ohms/foot is normal.

Also, when O2 sensors go bad they tend to get "stuck" lean and the PCM ends up dumping a ton of fuel in. If you have a lean code and the O2 sensor is black, the sensor is junk.

KED85

Mine does that and then it'll throw a code 32.
I say yours is the EGR, also.
Plug the line & see what happens.
My EGR valve likes to "stick" then cooperate.
My car hesitates upon partial acceleration, but if I floor it, smooth power.
When the EGR does cooperate properly, not a problem nor a code

CaliCamaroRS

Karl, the EGR won't cause hesitation from "2,900-4,500 rpms" as he stated. If it were stuck open, the engine would actually run OK at high RPM's.

firebird/intrep

you should try un pluging the negative terminal and leave it off for a few mins this will allow the cpu to reset and the problem should stop then yo will have to go out for a drive to let the cpu learn again

i guess all our cars are smaller versons of kitt

Nixon1

True, disconnecting the terminal resets the ECM and clears all trouble codes..but doing that is only really good for clearing codes. That and it's a good idea to do after installing new sensors to avoid confusing the hell out of the ECM......it's smart, but not THAT smart. But other than that, it won't really solve much. Doesn't take much of a drive to get it to learn again either..it learns extremely quick. Well, at least mine does. As soon as I start it up and let it stall because it's learning the IAC valve position, then it runs normal after that...doesn't even take a drive for mine..just idle.. Guess it runs exactly how it's supposed to? Lol..

TomP

I'd definately check out all of the items under the major tuneup... could be something as dumb as a plug with a gap that's opened up too wide, or a bad plug wire, dirty rotor, old air filter, timing, etc etc...

HALENAZ1

I had the same exact problem with my 87 2.8. It drove me nuts.... I though EGR..nope.. o2....nope.... plugs etc.... nope... then i unplugged my MASS air sensor... and there it was full power no hesitation. good idle. It seems that it was bad and it was leaning out my fuel too much.. I hope this is your problem also.

good luck

85f-bird

hey guys thanks for all the advice, i'll do some looking into the major tune up items and see what i need to check out, along with the other items on the list as well, being that none of them extremly difficult to do. The O2 sensor was replaced roughly a year ago i guess, as was the Fuel Filter (same time). Engien's still relitevely new, and has about 30,000 on the clock, was running alright until a few days ago, and with the MAF unplugged the car was running at about 900rpm (which is much nicer than eh, 500) but i didn't drive it, so i don't know if the problem with hestitation would have continued, but i'll test that tomorrrow also. Thanks again guys and i'll keep you posted....


P.S.
That LS1 third gen pix i've got are still on the freakin camera, think i've got like 3-4 pix left and once i waste them, i'll have the pix developed and on the computer.