Anonymous asked in Cars & TransportationMaintenance & Repairs · 7 years ago

1999 z24 cavalier idle/rpm problem?

been having problems with my rpms system in my cavalier (2.4 liter dual cam)

- in park it idles at 1000 rpm when it should be at 700

- when i release gas rpm Gauge jumps up and down but ok at higher speeds

- i replaced the iac( idle air control ) ran a lot better than it went bad to were it was before

- cleaned out this gross thick orange junk from near my oir air separator

- checked throttle body positioning sensor

-did a hot oil change and replaced oil filter

?could it be the oil air separator need to be replaced? or is the map sensor gone?

the issue about the same in hot and cold weather (seemed to be a little worst when there was snow out)

almost out of possible Solutions next to getting rid of car gonna. go to the Chevy dealer soon see if they can diagnose the issue

any Solutions would be great

1 Answer

  • 7 years ago
    Favorite Answer

    First do you have a check engine light? If so you should follow a flow chart for that code first before anything. If not, you should check for vacuum leaks. Being it idles around 1000rpms it seems like a small one. A few easy tests you can do. While the engine is running, press the brake while looking at the tach. Does it change rpm when you do? If so you may have a bad brake booster, if not, then check for other vacuum leaks. Get a can of brake parts cleaner and spray around the intake, throttle body, or vacuum lines. Be careful around the exhaust, brake clean will catch fire. If you have a leak from one of those locations it will change idle speed. If not, check the throttle body. Sometimes dirt and sludge can hold the throttle blade just a little open to where the IAC motor is trying to compensate for it. Carb cleaner and a old tooth brush works great for this. Also remove the IAC and clean in that area too. Try not to clean too close to the TPS because sometimes the cleaner can get into the sensor and mess it up. The best way to clean the throttle body is to remove it. Disconnect the battery first or you will have codes for tps, iac, or whatever in the system.

    Source(s): 14 Years Certified Mechanic
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