ive had this nasty idle problem with the car, its an 86 2.8L A4 sport coupe. doesnt run too bad at all, we just fixed the distributor oil leak. we start the car and it barely idles and we need to keep the RPMs a little up for it to idle, if we shift it into gear too quick it will stall out and die. once it warms up we can shift it into gear fine and it runs really good. its just before it warms up when its bad. it feels like its a dead spot in the low rpms when its cold. the car isnt registered since we just started working on it, so we cant drive it to go get codes taken from it, if its throwing any.

does this sound like something framiliar to anyone? vacuum leak? some kind of sensor? any help appreciated, thanks!

 

you can check the codes right in your drive way. Just use the search button and you'll find instuctions on it. In the Tech section on the main page of this site you can find a list of all the codes. Sounds like you may have a bad Cold Start Valve or even(more likly) some f'ed up sensors. Check the TPS Sensor witha digital voltmeter...oh wait, go out and buy yourself a Haynes manula or even better, TomP's bible (ray of light out through parting clouds, angels singing, etc.), the chevy repair manual. Both of those will run you through some basic checks and crap to do to get the car running better. Also do a search for the TomP tune-up here in this forum...makes the car run like new. Damn, Seems like Tom is the V6 ThirdGen ***.

 

anyone know if the 3rd gen codes are the same as 4th gen?

 

No they aren't. The 4th gen cars are all OBD2 as far as I know, and you have to use a special code reader to get them out...or go down to autozone and have them pulled.

There are A LOT more 4th gen codes, but they are way more specific. It'll tell you if one cylinder is misfiring and under what conditions it happened. They are WAY WAY WAY better that way, but unfortunatly, you have to have ht e reader to use it.

 

oh thanks for the info, makes me mad, my SES light comes on constantly

 

if I remember correctly, OBDII is 96 and later so the first few years of 4th gen should be readable.

 

mine has the pin thing in the same place as a 3rd gen, i figure ill try it, but i need a code list to see what im gettin, il probably try it with the 3rd gen codes tomorrow to see what comes up. im thinkin o2 sensor, ive recently been gettin bad mileage and kinda low power too, not sure if low power has anything to do with o2 though...

 

89cmrodriver - Grab the haynes manual for 4th generation. It will have the code list in there. I have looked at the 4th gen book before (my bro has a 97 camaro) but it has been a couple of years so it is foggy so I can't remember the test method off hand.

good luck!

 

i was plannin on doin that too...ill borrow it from the library...now wonder how id get a library card...lol

 

the check engine light is never on if that helps at all, does that mean that no codes are going to be there, or will they be stored or something? i always thought they were being thrown when the light is on, but this is confusing me now.

where is the cold start injector/system thing located? ive read about it but never actually saw it...

im going to check the fuel pressure and filter within the next week hopefully, can that be a cause of running bad when cold, but completely fine when cool? could this be a timing problem?

thanks!

 

my dad doesnt think its the fuel pressure, but now i read somewhere it might run bad wen warming up if it has low pressure, but can fix itself once warmed up? or did i read it wrong? it was in a post in the tech/general engine forum.

i was lookin around outside today, trying to see what this is, and all i know is there are no codes being thrown, so would that mean its something fairly easy to fix? could it be the 02 sensor, or would that trip the SES light? neighbor tested the TPS and it worked out fine, but how do i check for the cold start injector/valve thing? any help appreciated, thanks!

this car has been sitting for a while too, could it also be that?

 

there is a gm bulletin on this problem if i remember right it calls for changing to a new PROM(chip) and a new ignition module.

 

the bulletin # is 87-108

 

where do i go with that number to find out what to do?

or am i supposed to just get a new prom chip and ignition module and thats it?

 

you can go to your GM dealer they can pull up the bulletin and depending on which #PROM you originally had they can match it with the new #PROM. there is actually a few things the bulletin has you check beforew replacing those parts such as air leaks after the mass air. if they can't help you i will try to write up the whole bulletin

 

is there any place to do this online, or would a GM dealer still have the records if the bulletin has been around for over 10 years?

thanks a lot for the help though, woulda never thought. if anything, cant i just find a parts car and swap proms?

 

I think the online website alldata.com has what you are looking for perhaps. I might be wrong, but it might be worth a look or a start.

 

i searched around the boards, and thats exactly what i found. worked nicely, although it just verified the service code, it didnt tell me what to do. i dont know if a GM dealer would have records from that long ago, but im probably wrong hehe are there any reference prom #'s i can get on this site so i can compare it to mine, or is it more complicated than that? like do they varry according to year?

 

if you take your ecm down and pop the PROM cover off you will probably see a code on the top of the chip write it down and post it and i will see which one you need to replace it with

 

ah, i will do so tomarrow. i was searchin around tryin to figure out wether or not the prom code was on the prom itself, or if it was listed on the computer, or anything like that, but it was simpler than i thought, right on the prom itself. ill see what i can scavange up from it, thanks!

 

i should be able to get the code by the weekend or tomarrow hopefully. just got all our tools and stuff back, we had 99% of the garage in temporary storage at my grandmothers house while we redid some stuff around here.