I recently got a 91 gs and when you first start it, it jumps up to 3000 rpms then after maybe 30 secs, it will start jumping from 2500 down to 1200 to 1500 rpms, after a few minutes it used to idle at 750 but it hasn’t been doing it recently, I have been told that it could be the iacv but didn’t want to dish the money out if it wasn’t that. I’m only 16 and don’t know very much about cars, so explain in detail if you can think of anything. Also I think its the pcv valve hose going into the intake manifold but if not it was one of the hoses closer to the right side of the manifold and it had a hole in it and I was wondering if that could have something to do with it
Yeah, replace any hoses with holes in them first. You can also clean out the iacv. Google it, pretty easy stuff.
I’ve googled it, just thought you guys are pretty much specialists on these cars and could lead me in a good direction on what to do
be specific. what exactly is the idle doing? bouncing? loping? completely erratic? idling fast? is this only on a cold start? does the problem go away with time/temp? details are key
If it does it only when it’s cold, it might be the Fast Idle Thermo Valve (FITV). Here is an example: https://www.youtube.com/watch?v=YLvLO8dVyhg
well it basically just goes up and down in a rhythmic manner and it used to stop after about 5 minutes but now it wont and now sometimes after you’d drive for awhile and then start it again it would go up to almost 4k rpms and then go back to going up and down from 2500 to about 1200.
that sounds like you have a vacuum leak, or the fitv is stuck/sticking. with the vehicle at operating temp, remove the air cleaner duct. there should be 2 holes in front of the throttle valve, in the bore. iirc, the top hole is iac passage, lower is fitv. with the vehicle running and condition ocurring, block the the lower hole with your finger. hold it there for a minute or so. let the iacv do its thing. if the idle smooths out, the fitv is at fault. if so, you can try servicing it. if problem continues, with ducting still removed, cover the entire throttle bore with your hand. if the engine does not stall out quickly, you have a vac leak. there are multiple methods to finding it. but let’s see what we have first. try those 2 procedures and report back
Thanks a lot man! I’ll hopefully get around to trying that tomorrow.
Alright so after plugging the bottom hole the idle was normal
service the fitv. or replace if it’s too far gone
I found a good tutorial to clean it, thanks so much for the help!
no problem. happy you got it sorted