Odd problem with RPMs

I have an '01 Malibu with just under 77,000 miles on it.

Here's the symptoms: in the past two weeks, my engine suddenly decided that a proper idle speed was not 700rpm, but somewhere between 2500 and 3000rpm. This happened while I was driving; the rpms just climbed, even after I took my foot off the accelerator pedal (which didn't go down, by the way).

Automatics don't like shifting, but through keeping it in low gear or neutral I was able to make it to a place where I could pull off. I turned the car off, got gas (it happened to be a gas station), and it still went wacky when I turned it back on. Found a parking spot, turned it off again, did it several times; each time, same problem. Then I left it off for the half an hour it took for my dad to arrive. When he got there, I turned it on to show him what it did and - you guessed it - nothing. It idled just like normal.

The same thing happened yesterday as I was pulling into the parking lot at the apartment complex I call home; it just started accelerating, making it rather dicey to park. But this time, I turned it off, and turned it back on, and it was fine.

Several days ago, my car had some trouble starting, and the revs were wacky in a different way - varying by around 500 or so rpm in either direction without me touching the gas pedal. Or I'd be holding it steady, and it would alternately jerk forward slightly or fall slowly back. At the first red light, I shifted to neutral and turned it off, then back on again. No further problems that night.

My B-mobile's had weird electrical problems since I got her; one morning last January, the AC and fan, radio, clock, and display backlights died. Mysteriously, the headlights still worked fine, as did the accessory 12V outlet. Later that night, I turned the car off at a drive-through, and when I turned it back on all was well. This in spite of the fact that I'd run several errands during the day with everything staying dead when I turned the car back on.

So, what gives? I can make enough trading it in or selling it to pay off the rest of my loan, and at this point I'm thinking I'll do that and buy a Civic or Corolla that may have more miles, but will be more reliable.

I had that happen to me and my 99 Malibu from time to time. If I am correct, I think it had something to do with my intake manifold gasket when the valves started to go bad.

Thing is, I just had the lower intake manifold replaced a thousand miles or so ago. Any other possibilities before I decide to write off this car? Or can you tell me how this weird problem relates to the valves and the intake manifold?

Its like a power surge thing. The RPMs go crazy etc. but there is still drivability.

I drive a fair bit (238 city miles per week, non-commuting, averaged over three months), and this has only happened those three times. But when it does happen . . . this isn't the 4-cyl Malibu we're talking about. 170hp, 190lb-ft of torque at 2500-3000 rpm is a pain to stop. And dangerous if it were to happen as I was approaching a light - the area I live in, most of the roads have a speed limit of 45-55mph (non-interstate).

EDIT: I found that the nice fat tube running from the air filter to the engine wasn't clamped at all! Probably been that way since I got the intake manifold replaced - it cost me $550, you'd think they'd care enough to clamp the hoses. I have no idea if it could be at all related to my problem.

You problem sounds more advanced but my cam position sensors' wires became frayed from the hot coolant leaking out of my intake manifold gasket.

It caused my RPMs to jump around but not the problems you described.

Your original statement was correct "trade it in for a Honda or Toyota" and take a bath on the payments or negative equity.

I have had the same problem for some time on my 99. I have researched it and found it to be the low throttle sensor. I plan on replacing this weekend.

check the iac motor..it might be screwed up ...