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Idle drops 200-300 rpms

S

splicer7

PM 2024
Full Member
Joined
Dec 14, 2020
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2007 chevy avalanche 5.3 flex. Hello, I reticently replaced my x over with two catalytic converters and all 4 oxygen sensors. I was throwing codes for bad converter and or oxygen sensors quite a bit. Replaced all of it because it is 17 years old. Plugs changed 2 years ago and you should know i only drive it 6 months out of the year. Was hoping this would solve the problem when in drive and stopped. Idle drops say 200 to 300rpms intermittent. never stalls and when driving you never notice the problem. Gas mileage is still 15mpg same as it was when I bought it 12 years ago. Cleared the old codes out (Why the mechanic didn't is beyond me) hasn't thrown any codes for about a day now. Is it possible there is a re learning process for this.
 
Last edited:
are you sure tach gage is accurate?

DO you hear and feel it stumble to such low RPM.
I have seen them drop to low RPM but bounce back up to 500-600rpm like when at stop light and AC kicks on or off.
 
If the throttle body and mass airflow sensor have not been removed and cleaned with the correct cleaners, I would suggest doing this first to address wandering idle speeds.
 
ygmn said:
are you sure tach gage is accurate?

DO you hear and feel it stumble to such low RPM.
I have seen them drop to low RPM but bounce back up to 500-600rpm like when at stop light and AC kicks on or off.
Click to expand...
What I feel and what I see from the tach go hand in hand.
 
ygmn said:
are you sure tach gage is accurate?

DO you hear and feel it stumble to such low RPM.
I have seen them drop to low RPM but bounce back up to 500-600rpm like when at stop light and AC kicks on or off.
Click to expand...
Its when I'm at a stop light this happens. my ac never kicks on or off
 
Still sounds like throttle body Air Idle to me, MAF could be, Air leak after the MAF, Intake leak? If it were carbureted I would say the float was miss adjusted and sloshing fuel but a vacuum leak can have the same symptoms.
 
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