Bouncing Idle - How to correct?
#1
Bouncing Idle - How to correct?
How do I correct a bouncing idle? On a cold start the engine goes immediately to about 1,900 rpm, as soon as it warms up it drops to around 1,200 and then to around 800 and begins to bounce between 800 and around 1,400 rpm. It does not stay at the high or the low end for even a second - just keeps bouncing.
The car ('90 5.3L) has been laid up for months while working on an ABS problem (ABS Warning light continuously on), the only time it has been driven in months has been a couple of test drives to check the brake progress. Only the ABS system has been apart.
I have tried to do some searching in the archives and i have found a lot of information related to the AAV, but that all seems to be about high idle and not "bouncing" idle? Anyone with any ideas appreciated?
Greg L.
The car ('90 5.3L) has been laid up for months while working on an ABS problem (ABS Warning light continuously on), the only time it has been driven in months has been a couple of test drives to check the brake progress. Only the ABS system has been apart.
I have tried to do some searching in the archives and i have found a lot of information related to the AAV, but that all seems to be about high idle and not "bouncing" idle? Anyone with any ideas appreciated?
Greg L.
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What happens is the RPM climbs until the fuel (injector) cut-off kicks in. Then the RPM drops. Then the fuel is turned on again, and the RPM increases....and the cycle repeats and repeats.
The high RPM is caused by extra air coming from....somewhere. A stuck open AAV is common but it could be a vacuum hose having come off, air cleaner housing bolts loose.....
Remove the LH air filter but leave the base in place. Put you thumb over the (approx. 1-inch) hole in base for a few moments. Does the cycling stop? if it does, your AAV is stuck.
Cheers
DD
The high RPM is caused by extra air coming from....somewhere. A stuck open AAV is common but it could be a vacuum hose having come off, air cleaner housing bolts loose.....
Remove the LH air filter but leave the base in place. Put you thumb over the (approx. 1-inch) hole in base for a few moments. Does the cycling stop? if it does, your AAV is stuck.
Cheers
DD
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Greg
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