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I cleaned the MAS, the throttle body and waited 100 miles. The RPMs still go from 650 to 900 every 40 seconds for 10 seconds, then drop back down. Has an associated hum from the engine. Happens at stop lights and just idling in park in the driveway. Not a big deal, just might be a symptom of something else. Any ideas?
A Vacuum Leak after the MAS ... use a water spray bottle filled with water ... and (stream) spray around any junctions while the engine is running ... if there is a vacuum leak, the engine will immediately stumble and stall.
Issue clearly happened after MAF maintenance. What changed ? That is the question that needs to be investigated ... not A/C cycling. Slow and consistent RPM cycling points to a minor vacuum leak downstream from the MAF ...
A Vacuum Leak after the MAS ... use a water spray bottle filled with water ... and (stream) spray around any junctions while the engine is running ... if there is a vacuum leak, the engine will immediately stumble and stall.
I was going to say vacuum leak, based on experience with other vehicles, in that case it was the intake manifold gasket. But it could be a lot of things.
Issue clearly happened after MAS maintenance. What changed ? That is the question that needs to be investigated ... not A/C cycling. Slow and consistent RPM cycling points to a minor vacuum leak downstream from the MAS ...
Got it, not sure if it was similar issue that lead to the MAF cleaning/maintenance
Could also be an air leak downstream of the MAF in the intake path. Basically unmetered air is entering somewhere after the MAF.
My point exactly ... unmetered air entering the system downstream from the MAS sensor ... so the closed-loop system is attempting to reconcile via adjustment to the air-fuel ratio ... hence the "RPM Hunting" ...
I was going to say vacuum leak, based on experience with other vehicles, in that case it was the intake manifold gasket. But it could be a lot of things.
OP stated the MAF Sensor was cleaned. The problem started immediately after this maintenance ... so why would you go outside of that by suggesting anything that in no way related ? Sorry ... but no logic whatsoever ...
OP stated the MAF Sensor was cleaned. The problem started immediately after this maintenance ... so why would you go outside of that by suggesting anything that in no way related ? Sorry ... but no logic whatsoever ...
Because you have to remove several things in order to gain access to the MAF and the TB. If you don't put it back right or a gasket is missing you get a vacuum leak. Also if the MAF got contaminated, used the wrong cleaner, bent the TB plate you get all sorts of issues. We cannot guess what happened during the cleaning, the OP needs to go back and re-check everything, if still has issues can try to disconnect the battery, smoke test the system, start throwing parts at it eventually.
Wen quality gas is used and air filter is replaced regularly cleaning the TB or the MAF is completely unnecessary in my opinion. I have vehicle with 170k miles and while visually checked the TB for excessive deposits it was not once cleaned. it has no issues of any kind.
OP stated the MAF Sensor was cleaned. The problem started immediately after this maintenance ... so why would you go outside of that by suggesting anything that in no way related ? Sorry ... but no logic whatsoever ...
Have you ever cleaned your MAF? Are you saying there is no possibility of an air intake leak caused by doing the MAF cleaning? Please enlighten me with your "logic", Mr. Spock.
03-16-23, 11:52 PM
Idle speed rises every 45 seconds, then drops
