Ross Posted February 8, 2006 Share Posted February 8, 2006 When slowing down in gear, for some reason the engine surges as it goes between 1500-1400ish rpm. Feels like the throttle is being opened slightly, but its not! Seems to do it fairly consistantly. No ecs light. Idle switch is adjusted correctly. Any ideas? Maybe a sticky VAF sensor? Link to comment Share on other sites More sharing options...
hatchsub Posted February 8, 2006 Share Posted February 8, 2006 Im going on my experience with fuel injection from my IROC camaro seeing as how ive never owned a fuel injected suby. It "could" be the IAC (idle air control) valve. When mine was messed up it caused my camaro to surge coming to a light. Link to comment Share on other sites More sharing options...
naru Posted February 8, 2006 Share Posted February 8, 2006 When slowing down in gear, for some reason the engine surges as it goes between 1500-1400ish rpm. Feels like the throttle is being opened slightly, but its not! Seems to do it fairly consistantly. No ecs light. Idle switch is adjusted correctly. Any ideas? Maybe a sticky VAF sensor? I would play w/the dashpot adjustment.It slows throttle closure after all. Link to comment Share on other sites More sharing options...
Ross Posted February 8, 2006 Author Share Posted February 8, 2006 I would play w/the dashpot adjustment.It slows throttle closure after all. Yes, but this happens even after decelerating from say 3500 rpm at closed throttle - feels totally normal except for a half second long surge as it goes through 1500rpm, then its fine again. I'll check it out though. IAC valves can certainly cause strange problems on some cars, but the valve on the ea81t is a simple temperature controlled unit, and i don't think it could open/close quickly enough to cause this problem. Link to comment Share on other sites More sharing options...
carfreak85 Posted February 8, 2006 Share Posted February 8, 2006 I would check the throttle cable for fraying. I remember that after I reinstalled my engine I also had to replace the throttle cable. If it has to make any tight bends it can wear out. Link to comment Share on other sites More sharing options...
Ross Posted February 9, 2006 Author Share Posted February 9, 2006 Hmm, just noticed another oddity - if its idling, and i pump the brake pedal, the engine will speed up by about 200rpm for a second or so.......If i hold the brake pedal down, the idle doesn't seem to change though. Leaking booster or something?? Link to comment Share on other sites More sharing options...
naru Posted February 9, 2006 Share Posted February 9, 2006 Hmm, just noticed another oddity - if its idling, and i pump the brake pedal, the engine will speed up by about 200rpm for a second or so.......If i hold the brake pedal down, the idle doesn't seem to change though. Leaking booster or something?? Every time you pump the pedal you are emptying the booster vacuum chamber into the manifold.This is unmetered air.Since RPMs increase you must be a liitle rich.Monitoring the O2 sensor output voltage could prove entertaining. Link to comment Share on other sites More sharing options...
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