94 3.4 rough idle and accel when cold

hey i have a 94 3.4, and i have noticed recently that it has cold running problems, serious ones. the other day, the car took a bit to start (it was about 45 degrees outside, and i havent had the car long enough to know how it runs on cold days), and everytime i start the car in the morning, regardless of outside temp, the car runs like absolute shit until it gets up to operating temp and stays there for a bit. every time i let off the gas, the tach drops to 500 and acts like its gonna kill, and when i come to a stop, the engine stumbles all over itself, first dropping to the 500 mark, and then spiking a few times to 1000 (normal idle) until about 3 minutes later the idle will level off at 1000. then when i accelerate, there is almost no power, and the car jerks really bad. i have also noticed at operating temerature, a slight lack in power, and every now and then it wont accelerate smoothly. i have been advised that this sounds like a vacuum leak, but i cannot find one, and just before this started, i replaced all the vaccum hoses. recent repairs include a new upper intake manifold and gasket (the car ran fine after this repair for about 2 days until i replaced the vacuum hoses). i do know that the egr is bad, but it has been bad for months, and this problem just started.
please help as i am a delivery driver and i need this car to make money!

please help as i am a delivery driver and i need this car to make money!

Hey! Where you workin at man? I'm at Domino's myself. Sounds like you have a misfire man. I had a similiar problem a while back. Does the whole car seem to vibrate and shake really bad? If so then it is most likely a misfire, if you havent already, change out the plugs and wires. And make sure you stay with the ACDelco plugs, they're cheap and work great. There's no need to waste you money on the other overpriced mumbo jumbo NGK stuff.

it doesnt shake that bad (no more than normal) and i just fixed a misfire problem (a blown fuel injector fuse) so i know how it feels. plus would a misfire only happen when cold?

P.s. i work at pizza hut:grinyes:

my thinking right now is that one of the coil packs is goin out (since i just replaced all plugs and wires) and it is making a weak spark that cant ignite the mixture when cold, but is enough to ignite it when hot. anybody think this is possible? and if so, how do i check the primary and secondary coils?

my thinking right now is that one of the coil packs is goin out (since i just replaced all plugs and wires) and it is making a weak spark that cant ignite the mixture when cold, but is enough to ignite it when hot. anybody think this is possible? and if so, how do i check the primary and secondary coils?

It could possibly be your coils, they're pretty cheap at autozone, somewhere around $20 a pop. I'm not sure how exactly to check them to see if they're still good, but I'm sure there is a simple remedy that someone here knows of. That's a good idea though, might be why mine misfires after it hasn't been driven for a while. I know you can find out which cylinder is misfiring by checking the plugs, if you find one or more that have alot of carbon build up on it, then that would be the cylinder misfiring. Have you changed the fuel filter by any chance also?

btw, I used to work at pizza hut til they fired me after I had already quit.

changed the coils today, waiting for tomorrow to check if its still screwy. never changed the fuel filter, but i didnt consider it because of the fact that the problems pretty much started overnight, and the filter wouldnt have gotten clogged that quickly... i have a few friends (ex co-workers) with the same story.

Does it have a mass airflow sensor?

Does it have a mass airflow sensor?

Nah, 3.4's have speed density sensors.

changed the coils today, waiting for tomorrow to check if its still screwy. never changed the fuel filter, but i didnt consider it because of the fact that the problems pretty much started overnight, and the filter wouldnt have gotten clogged that quickly... i have a few friends (ex co-workers) with the same story.

Eh, still couldn't hurt. Only takes like 5-10 minutes to do. Might help?

problem solved! the coils did it, no more rough acceleration. thanks for the input though. yeah the 3.4 doesnt have a maf but is it a speed density sensor? i thought it was a throttle position sensor. one more question while i have this thread open... my horn/cigarette lighter fuse keeps blowing, and i figured it was the cig lighter because i wired them in myself (the car came without them) but i cant find a short anywhere, i was wondering if there is a common problem spot on this car or something, anything to make my life easier ive gone through like 5 fuses in the last month. they usually dont blow right away, it could take anywhere from an hour to a week, which tells me that the short is on a wire that moves and the fuse blows when it makes contact to ground. any input?

problem solved! the coils did it, no more rough acceleration. thanks for the input though. yeah the 3.4 doesnt have a maf but is it a speed density sensor? i thought it was a throttle position sensor. one more question while i have this thread open... my horn/cigarette lighter fuse keeps blowing, and i figured it was the cig lighter because i wired them in myself (the car came without them) but i cant find a short anywhere, i was wondering if there is a common problem spot on this car or something, anything to make my life easier ive gone through like 5 fuses in the last month. they usually dont blow right away, it could take anywhere from an hour to a week, which tells me that the short is on a wire that moves and the fuse blows when it makes contact to ground. any input?

Yeah, speed density, you know.. that little sensor that plugs in your intake elbow. It has a throttle posistion sensor, but that for your computer so it can know how much you have the throttle presssed so it can compensate and add more fuel. Speed density lets the computer know how hot or cold it is, so it can adjust the mixture of fuel needed. As for your cig. lighter. I'd have to say check all the wires in full detail. There could be a short in your ground somewhere. And make sure you're using the right sized fuses.

ok i understand that speed density thing now ( i learned it was an intake air temp sensor). the fuse is right so i guess im gonna have to find a short...thats what i was afraid of.

ok i understand that speed density thing now ( i learned it was an intake air temp sensor). the fuse is right so i guess im gonna have to find a short...thats what i was afraid of.

It is an IAT (Intake Air Temperature) sensor. Speed density is just the name given to the syetem. I just used the IAT sensor as an easy way to tell the type of system you have. I suck at explaining things :licka:

I was beginning to wonder...Speed density and IAT aren't even close to the same thing. I had to go study on it. It's basically and older style MAF, right?

I was beginning to wonder...Speed density and IAT aren't even close to the same thing. I had to go study on it. It's basically and older style MAF, right?

Yeah, it was out before MAF's were as far as I know. But it's still being used in some cars today. It does have it's advantages and disadvantages.