Idle issue
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 2,604
Likes: 0
From: Phoenix, Arizona
Idle issue
Driving home from work today my idle suddenly went to ****. Had the a/c on and every time I'd come to a stop my once normally idling (around 900rpm) LT4 would barely maintain an idle. Turn the a/c off, a little better but not much. Seems the idle was searching and, although it didn't stall, it was struggling to stay above 500. Car has some mods as listed but has been tuned and has run great for months, a/c on or off. This problem seems related to the a/c somehow because when I turn it off it idles better, yet still not the way it did before the problem. other than the idle issue the car runs fine. When I got home I checked for a vacuum leak but found nothing. Also thought it may be alternator related but the digital gauge is reading between 13.7 & 14.0 - pretty steady. Not sure really where else to look especially since I'm getting no codes.
Any ideas?
Thx,
Jeff
Any ideas?
Thx,
Jeff
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 2,604
Likes: 0
From: Phoenix, Arizona
Man, I just put in a couple of new .02's (NGK's) & I have been seeing a PO1153 & PO1133 (02 related) on occasion. The idle has never been affected before when these codes pop up but obviously something is up.
IAC is also a possibility but w/ no codes pointing that way, who knows?
Well at least I have someplace to start now. Keep the ideas comin'....
Thx
IAC is also a possibility but w/ no codes pointing that way, who knows?
Well at least I have someplace to start now. Keep the ideas comin'....
Thx
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
A place to start would be to clean the TB/IAC if it hasn't been done in a while. If it only happens after the engine is warm it could point to O2 sensors. How does it idle when first started? (hunting, surging)
Instructor
Joined: Jun 2006
Posts: 143
Likes: 0
From: Plano Texas
Originally Posted by RRT vette
A place to start would be to clean the TB/IAC if it hasn't been done in a while. If it only happens after the engine is warm it could point to O2 sensors. How does it idle when first started? (hunting, surging)
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Originally Posted by BlueMonster94
I have a 1994 Vette with a similar idle issue. When cold the engine idles okay, but when hot the engine idle surges to over 1500 rpm then drops down and back up again. I did have a vacuum leak, fixed it, but it didn't help the problem. Concurrent with this problem is the cruise control does not work although the speed sensor is new.
You may have a bad O2 sensor(s) which would only cause your idle problems when engine is hot. Could also be your IAC sticking or slow to react. If it hasn't been done in awhile, I would remove TB, remove TPS and IAC from said TB, clean the heck out the TB with TB cleaner, then carefully clean the spring and plunger section of your IAC.
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Instructor
Joined: Jun 2006
Posts: 143
Likes: 0
From: Plano Texas
Originally Posted by MikeC4
Did you dump your error codes to see if you have O2 sensor errors. O2 sensors are ignored by ECM during initial startup(open loop operation), and don't come into play until they have reached a certain temperature(closed loop operation).
You may have a bad O2 sensor(s) which would only cause your idle problems when engine is hot. Could also be your IAC sticking or slow to react. If it hasn't been done in awhile, I would remove TB, remove TPS and IAC from said TB, clean the heck out the TB with TB cleaner, then carefully clean the spring and plunger section of your IAC.
You may have a bad O2 sensor(s) which would only cause your idle problems when engine is hot. Could also be your IAC sticking or slow to react. If it hasn't been done in awhile, I would remove TB, remove TPS and IAC from said TB, clean the heck out the TB with TB cleaner, then carefully clean the spring and plunger section of your IAC.
