rough idle

hifooy07 · Posted: Sun Nov 15, 2009 10:17 am Post subject: rough idle

my car idled kinda high before around 850 to 900rpm but i recent changed the rocker arms to the 1.6 ones now it doesnt want to idle, just stall out sometimes or it will idle really high about 1100rpm then like 2min later it will jump up to 1300rpm if i touch the gas it will drop back down to 1100rpm. check engine light comes on when it goes to 1300rpm i checked the code, says its the iac so i changed it out with a spare it still does it. so i grab my other spare it does the same thing. any ideas?

SuperDave · Posted: Sun Nov 15, 2009 10:54 am Post subject:

did you take off the TB or the upper intake when you changed the rockers?

Sounds like a vacuum leak to me...

scott0999 · Posted: Sun Nov 15, 2009 11:57 am Post subject:

pmaniac69 · Posted: Sun Nov 15, 2009 3:28 pm Post subject:

did you hook up all vacuum lines? I did the same thing just yesterday, was going down the road and noticed my cruise or my heater controls didn't work

I kind've forgot the big fat vacuum hose

you must've forgot something, cause after I put mine on, the car starts easier, revs smoother, and idles like a dream

hifooy07 · Posted: Sun Nov 15, 2009 5:33 pm Post subject:

ill check the vacuum lines i thought that at first so i sprayed starting fluid around all the vacuum lines and intake gasket. i did take off the tb and upper intake bought new gaskets and stuff. ill just have to really search it just sucks all the vacuum lines go under the plenum...

hifooy07 · Posted: Mon Nov 16, 2009 9:12 pm Post subject:

checked everywhere grabbed a can of starting fluid sprayed the entire intake manifold got nothing sprayed all the vacuum lines under the intake manifold nothing... im lost. noticed today it didnt want to idle at all stayed at about 500rpm till i got it warmed up then it went to 900rpm idled fine then moved back up to 1100rpm. when it gets colder its harder to keep it running. seems like when it gets warmed up its not as bad.

hifooy07 · Posted: Tue Nov 17, 2009 11:26 am Post subject:

looked again today. soaked everything with starting fluid nothing. its a vacuum leak for sure at 750rpm i only have about 10" of vacuum im having hard time tracing it out everything seems fine. maybe my spare iac is bad too is this possible? anyway to test them?

pmaniac69 · Posted: Tue Nov 17, 2009 5:46 pm Post subject:

IAC doesn't run off of vacuum, MAP sensor is the only one I can think of that you might have damaged, but I doubt it

hifooy07 · Posted: Tue Nov 17, 2009 6:58 pm Post subject:

took the upper intake manifold back off. found that it was leaking really bad the rubber gasket ripped. replaced it, started it up it still does it... only when its cold, it will not idle. once it warms up, it will idle at 850rpm but shows like 14" of vacuum maybe 15" then moves up to 1100rpm. i cant figure this out i tried another map sensor no changes. i sprayed starting fluid kinda under the intake manifold no changes im going nuts it is seriously a pain in the balls to keep running when its cold. will the egr effect this? when the motor is cold it would richen the mixture so that should kind of make up for a vacuum leak wouldnt it? therefore it would be running a decent mixture so i should be able to rule that out.

would it be possible to buy rubber vacuum hose and run them on top of the plenum? ill just replace all the lines just to rule it out. im gonna try to do it with out taking the upper intake manifold off. dont feel like going through that pain again.

hifooy07 · Posted: Sun Nov 22, 2009 10:08 am Post subject:

changed all the vacuum lines and it still does it... i need a gasket what is the gasket that is on top of the throttle body where the vacuum lines come into and the iac is connected too. i went to napa and dude had no idea what it was. he came out and looked and still didnt know what it was. i looked on line and couldnt find it either what is this called? any other suggestions? still will not idle when cold. when its cold it tries to idle at 450rpm and surges up and down. i swapped out the map sensor with a spare it didnt effect it.

pmaniac69 · Posted: Sun Nov 22, 2009 11:09 am Post subject:

be silly and see if there are any codes stored in the computer

I wonder if maybe you CTS is going bad, your o2 sensor, or a combination of both

scott0999 · Posted: Sun Nov 22, 2009 11:43 am Post subject:

have you tried disconnecting the battery and doing a idle relearn?

hifooy07 · Posted: Sun Nov 22, 2009 10:02 pm Post subject:

yep disconnected the battery for 10min. hooked it back up and same thing low idle about 400rpm keeps surging 60rpm 450rpm up and down till it warms up a little then it will idle at 1064rpm if i let it sit for like 2min the check engine light comes on and idle moves up to 1300rpm. checked the code it says iac. im tempted to buy a new iac but its $50 dont want to buy it if theres nothing wrong with it. im just going nuts with this my gas mileage sucks its hard to drive. i have a new o2 sensor and cts maybe ill try throwing them on just to try and eliminate things. my vacuum is kinda low when its idling at 1100 rpm its like 12"
any idea what the gasket is called that sits on top of the tb? where the iac connects too and the vacuum lines

hazez24 · Posted: Mon Nov 23, 2009 10:47 am Post subject:

I know what you're talking about but not sure what it's called. It's basically like the main vacuum connector with the 3 or 4 lines going into it and then it all connects to the iac on the TB. Might just be a junk yard part. try puting a little silicone around the edges and what not if you think that's what it is. My brother went through two of those turned out his ecu was junk so he had to change out the ecu and prom chip.

jrh7535 · Posted: Mon Nov 23, 2009 5:20 pm Post subject:

i had the exact same problem. the piece is a junk yard part. got mine for five bucks. they get dri rotted easily. i went to the dealer and there is only one out there and they only would sell the whole assembly, its the piece and all the lines connected to it. it was 45 bucks and in South Carolina. F that.

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