I've had this problem ever since i bought this car. It's a 2000 cavalier w/3spd. automatic.
It does the following bizarre things:
1. idle is unsteady, goes up and down, sometimes in an alternating pattern, sometimes intermittently. i can feel the rpms pulsing in the steering wheel and by the engine noise.
2. When letting off the gas at low speeds, the engine rpm's drop. If i'm in park, and i tap on the pedal, the engine revs, and when it goes back to idle it dips far below idle speed and almost dies.
3. At 75-80mph, or otherwise working the engine hard at any speed, the rpm's pulse slowly. the rpm fluctuates about 100rpm in a cycle lasting about 2 seconds per high / low pulse. ( does that make sense? )
This problem gets *really bad* when the spark plugs are going out. When i changed my coil packs to msd blasters, the situation improved, but this still troubles me.
I disconnected the front oxygen sensor and drove around a bit and that seemed to help too.. the rpm's were still pulsing, but not as hard.
any clues? fuel pump? fuel filter? something else? I've been dealing with this issue for over a year now and it's really frustrating.. two mechanics have already told me they 'don't know'.. grr
Sadly, no more..
May be a vacuum leak. You should check to make sure you have nothing loose under the hood. Also, check to make sure your injectors are sealing properly. A buddies civic did some funny stuff because one of his injectors wasn't sealed. In his case it would rev from idle to about 2,000 rpms whenever he wasn't driving. So at every stoplight everyone thought he was trying to race. Quite embarrassing.
Hey, I got the same odd off-idle speed 200-400 rpm wide rev flutter during off-pedal low speed coasting with my '94 2.2 auto-trans while in gear. Anybody got a clue why?
Go beyond the "bolt-on".
Sean McCoy wrote:May be a vacuum leak. You should check to make sure you have nothing loose under the hood. Also, check to make sure your injectors are sealing properly. A buddies civic did some funny stuff because one of his injectors wasn't sealed. In his case it would rev from idle to about 2,000 rpms whenever he wasn't driving. So at every stoplight everyone thought he was trying to race. Quite embarrassing.
Had this issue with mine. It was my air flow sensor that was shot. Made the engine rev for nothnig bad sensor making the engine think its starving from air.
