Car Revs On it's Own While in Cruise
 

So, my car is pretty mint. It's a 94 z28 and I only have 35k miles on it. The body and interior are in perfect condition and the engine is very clean and strong. It's been really cold for the past few months and it doesn't hesitate to start even in the worst of conditions. It also drives beautifully.


The only issue I seem to have is that occasionally the car will literally start to rev itself up when I come to a light or am stopped. RPM moves and all. It will start to jump and when I take my foot off the break it will start driving on its own. It doesn't take off at high speed or anything, but it would probably get to 20 mph on its own if I just let it go. It's basically driving itself. It really only seems to do it when cruise control is on, which is a feature I couldn't care less about anyway, but still. I don't drive it on cruise and didn't realize it was even on before, so I'm just doing without and that's fine; but does anyone have any idea what the issue could be? It may have done it once or twice with cruise off. I’m not sure, but it definitely isn’t common if so and I can’t say for sure if it has even done this while not in cruise… I just think it may have a little.


Thanks in advance everyone.

You're welcome!
Are you getting a check engine light? My first thought (if it only happens when cruise is not on) would be it's idle air control valve (IAC) related. Paying close attention to exactly when it does and doesn't happen would be helpful. If the IAC valve itself were bad though, high idle would happen separate of cruise control. Could still be the IAC, and when it happens to you (cruise on or off) might be a coincidence.

You know, it did it yesterday on my ride home from work, with cruise off. So I suppose it's happening regardless. It wasn't as bad, but it did do it.

Could it be a leak in the vacuum hose maybe? I feel like it does it more often when it's really cold out, didn't have the problem until the weather changed. Maybe the hose got a bit brittle with the cold and caught a crack.

It's really annoying me. The thing looks and drives amazing, and this sort of dampens the ride.

try cleaning the iac it may be sticking. does it hold the rpms after speeding up or does it rise on its own? have you changed or oiled the air filter recently?

for the low coolant light look at 13 and 14 here 4th Gen LT1 F-Body Tech Aids

Thanks Craby, I'll make sure to clean out the iac. Haven't done it yet, been freezing and I'm only driving it 2 days a week for a total of about 28 miles all together. I'm getting an Eldorado on Monday as my all season ride and I'll probably be storing the Camaro until June or July, and then I'm taking it off the road in August. I'm really adamant about preserving this car with low miles. 2-4 months a year is all I plan on driving it, aside from the odd clear day in winter, just to keep it loose.

I'm not too sure what you mean as far as asking if the rpm holds, I've always been into cars, but I'm now just getting into their inner workings and such. I'm still new to some terminology, sorry. Once I start driving it's fine, it's just when I come to a complete stop that the engine starts to rev and rpms will oscillate, sometimes more than others. I hope I didn't screw anything up. I had it on cruise control for probably a few thousand miles and didn't realize. When I was getting to 50mph it was kicking, because I was essentially fighting with the cruise control and had no clue. That may have somehow caused it, since it wasn't doing it for the first few thousand miles I had it. My mother took it a few times, she had a 68 Camaro, so I let her, and I'm pretty sure she put it on, but regardless of who put it on, it was on for some time.

I also haven't changed or oiled the air filter, it may have been done by the previous owner, but not since I got it last June. I've had it serviced, had the fluids checked, but no one mentioned anything other than that it was a great car. I will look into it though. I want to start doing something’s on my own, so an air filter may be a good place to start.

change your pcv valve, cheap and may be it.

once you put the brakes on the cruise control disengages. i doubt its got anything to do with it.

the iac would be one way it could raise.

another is a vacuum leak. if its doing it when the brakes are applied i would check the power brake assist to see if its leaking. maybe pinch off the assist vacuum hose when the idle is up and see if rpm drops.

for the heck of it check egr valve to see if its dirty.