need help diagnosing problem
need help diagnosing problem I have an issue that I think is either a vacuum leak or a IAC going bad. I thought it was electrical, but maybe not. I used Autotap and a Snap On scanner...no codes at all. BUT, when I did a test on the IAC with the scanner it would idle up to 1200+rpm's, but would not go to the lowest seting (270 rpm), would only go down to about 680 rpm or so. Does this mean the IAC is bad?? My car is idling a little high, and when in gear it will idle up to 45 mph by itself (it shifts to third and keeps at 45 mph with no gas applied). The car runs like **** at WOT, not nearly as powerful as before. It surges as well, and if I brake, it surges and comes to a normal idle.
I have done the following:
disconnected the timing tuner
disconnected the battery
Autotap'd (no codes)
Snap On scanner (no codes)
checked plugs
wires are 1 yr. old
Coolant system pressure test (to check for leak at manifold), perfect
car was running great, then I replaced plugs, fuel filter, cleaned nitrous filter, oil and filter, tranny fluid and filter, front brake pads, new 160 amp alternator, put a breather in valve cover, removed voltblaster (was unhooked so it was not used)
...seemed to run great afterwards. I was runing the nitrous that was left in the line, ran hard, then the fuel got it too rich. It set a check engine light, then I drove it a few minutes and it went off. Next time I ran it two days later, it started and ran fine until I went WOT, it was down on power (on and off the bottle).
Any ideas? I will buy some carb cleaner and spray to try to find some potential vacuum or gasket leaks...
SDB
I have done the following:
disconnected the timing tuner
disconnected the battery
Autotap'd (no codes)
Snap On scanner (no codes)
checked plugs
wires are 1 yr. old
Coolant system pressure test (to check for leak at manifold), perfect
car was running great, then I replaced plugs, fuel filter, cleaned nitrous filter, oil and filter, tranny fluid and filter, front brake pads, new 160 amp alternator, put a breather in valve cover, removed voltblaster (was unhooked so it was not used)
...seemed to run great afterwards. I was runing the nitrous that was left in the line, ran hard, then the fuel got it too rich. It set a check engine light, then I drove it a few minutes and it went off. Next time I ran it two days later, it started and ran fine until I went WOT, it was down on power (on and off the bottle).
Any ideas? I will buy some carb cleaner and spray to try to find some potential vacuum or gasket leaks...
SDB
TECH Enthusiast
Joined: Apr 2004
Posts: 749
Likes: 0
From: Chandler, Arizona
My car started idling like it was possessed. It would accelerate on it's own, etc. I also was not getting any codes. I pulled the IAC valve and cleaned the heck out of it and the throttle body with WD40. Fixed all my problems.
I would most definately check for a vacuum leak. After installing my LS6 intake i ended up having a vacuum leak. My car would idle around 1300 rpm and it ended up throwing a code that was like Idle speed high or something and on the scanner it was running really lean. If i had it in gear it would idle up to 45mph or so. First I would make sure the IAC is plugged in completly then take it out and clean it and if that doesnt fix the problem take some carburator cleaner and spray around the intake while it is running like you said. Good Luck.
thanks, thats what I was thinking...good to hear that is is probably related to IAC and/or vacuum leak. Hope I can just clean IAC instead of getting new one ($126). Will do this and see if it works.
SDB
SDB
