94 3.4 auto high idle????

[Strangler]

Hello, lurked for a while and now I need some help. My wifes daily driver is a 94 Camaro Coupe with the 3.4 and an auto. The car has 100k on it. Within the last week she started telling me that as she tipped into it to leave from a stoplight or while in traffic that the encine would stumble once... drop to 200rpm.... and then regain normal throttle input. I drove it yesterday in an attempt to diagnose, but all I noticed is that its ideling at 2100....

So, any chance the TPS went bad and its running in limp mode or something? Its not showing any codes, and performance seems as lackluster as always, So what controls the idle speed? Thanks guys, I didnt feel the need to tear it apart before asking around. Its great to see a site dedicated to the baby engines..... there are a million of them out there. -Scott

[cam98aro]

it could be the mass airflow sensor, or the IAC

[FunkZ]

Well it's definitely not the MAF, 3.4's don't have one. Could be the IAC. Or a vacuum leak.

[cam98aro]

Originally posted by FunkZ:
Well it's definitely not the MAF, 3.4's don't have one. Could be the IAC. Or a vacuum leak.

heh.. sorry about that one, i was thinkin of my dads 3.4L impala [img]redface.gif[/img]

[Strangler]

I changed the IAC today and it cured the off idle tip-in problem, but the car is still ideling at over 1000 rpm. Hosed every visiable conection with brake cleaner and recieved no increase in RPM, so I dont think its a vaccum leak. Any other ideas? At least its better...

[vallentinerocks]

I just had a similar issue in my 94. i removed and inspected the IAC first, and checked it with a meter. seemed OK, so my next step was to reset the computer. disconnect the battery lead for 10 minutes or so and reconnect. Know that you may have some things to reset like the radio presets and such. the computer reset took care of my high idle. try this before replacing anything else. hopefully it will cure the idle. normal idle is around 800-900 rpms. good luck. if not, you may have to check some of the other sensors.

[vanbibber]

just throwing this out there. but check fuel pressure to see if its fluctuating when the rpms drop down like that. maybe the fuel pump is on the way out. not sure if thats the problem but its worth checking.

also check around the intake and the plenum for vaccum leaks.

[vallentinerocks]

Stranger, well here we go again. So i suggested to disconnect the battery and reset the computer,(still go ahead and try it if you havent done so yet), however, my idle issues are back as of this morning. so i reset again, and idle was back to normal for a while, but its not always dropping back down to normal idle. sometimes up 100-600rpms over normal idle. So i took IAC off and cleaned it this time and see if that would help. still, its idle is changing at random times. guess im gonna go ahead and put a new IAC in and see if it is the issue. this time was worse because after i put it back on and was test driving, my SES light would go on and off randomly as well. thank god it didnt do that two weeks back with i got my smog done, they would have failed me maybe (SES light right now does not go on and off when sitting, only when driving). I'll let you guys know how it goes after putting a new IAC in. Let me know how your situation turns out as well.

[vanbibber]

yours sounds like a bad EGR /\/\

[vallentinerocks]

Bad EGR? crap! i know they are sorta pricey. My car just did pass smog two weeks ago. gonna try the IAC first. Also decided to invest in an OBII scanner to read codes. will these things tell me IF it is a bad EGR or bad IAC an so On??? I have a Chiltons manual and it has several code tables in that book. will they cross reference with the OBII scanners? Please see my post on scanners if you know a little about them. thanks.

[MattM450]

i got my egr valve on ebay for 100 bucks

[vallentinerocks]

put in new IAC this morning. everything seems like it should so far. idles smoothly at around 900rpms and so far no more momentary SES light. i was wondering if the cleaner i used on the old IAC was causing the SES light to come on. i did not let it dry completely before putting it back on, and i read that oil on K&N filter recharged can cause SES light to go on and off, and was wondering if a cleaning spray agent could cause this as well. anyways, so far so good with the new IAC. drove it about 20 minutes and got on the freeway too. no high idle issues and no SES light. let you know if it messes up again. if it does, i will get diagnostics done first or buy my own code scanner before replacing any other parts. havent checked for vacumm leak, just had tune up and just passed smog. hope the EGR valve is not the problem.

[T-Tops3511]

Make sure you check your gasketts... Intake manifold gaskett, Throttle body gaskett. I was idling over 3000rpm.. Changed all my old gaskets and I was good to go.. Idling now at around 800-1000ish. I can almost guarantee that's your problem... JUst a pain in the but to do...

[vallentinerocks]

Day 2, still no more high idle issues. IAC may have been it. idling right at 900. ill keep in mind about the gaskets.

How 'bout you Strangler? figure out your idle problem?

[vallentinerocks]

Re: 94 3.4 auto high idle????

so it was an OBD I/ OBD II scanner.... hahaha. oops.

MAP sensor was problem.