Idle bouncing?

[Erik]

When i start my car (93 pontiac sunbird) it bounces around 300-500 rpm. Once i start driving, the bouncing stops wether it is coming to a stop at a light, or about to turn the car off, it doesnt bounce anymore, it is only after starting the car up. Is that anything that is serious? If confused, just ask..i suck at explaining. Maybe ill post a video.

[Erik]

8:45 bump for some help :rolleyes:

[Metalhedd]

that sounds really low for idle to me. most cars idle around 900-1000

[Erik]

ohh sorry, i mean it bounces from around 900 to 1200, 1400. I didnt mean idling at 300-500...thats the range its moving. Sorry i didnt even catch that.

[QCs_R4_Girls]

If there's no CELs, more than likely it's just because of the cold weather we've been having.
When the car starts up, it doesn't run on its default operating settings. Instead, it's on an open-loop warm up program that is monitored by coolant temp, MAF, rpms, and throttle position. In short, it's trying to get the operating temperature up as fast as possible. It's also sucking gas fast, so I bet your mileage is going down. (At any throttle position during the winter, the air that is sucked in contains more molecules/sq in so the fuel ratio needs to be adjusted (upped) to compensate, or else the mixture leans out.) Still with me?
If there are codes, however, it could be a faulty O2 sensor, leaky manifold gasket, clogged throttle body, or bad TPS. But since you didn't mention the car throwing codes, so you probably don't have to worry about any of those.

[cburwell]

Most cars have something that controls the cold idle. It sounds like there may be a problem with that unit since the problem disappears after a while.

The information that QCs provided is a really good explanation. It's worth checking those items out first.

[Metalhedd]

could be throttle position sensor, or like was said before, it could be normal for your car to warm up that way

[DPancoast]

- vacuum leak
- coolant temp sensor
- air in the coolant system
- TPS out of calibration
- sticky throttle cable/sludged up throttle plate....
- O2 sensor may be dirty....

could be a laundry list of things. Start with checking the simple things first.

[S4toSTI]

If there's no CELs, more than likely it's just because of the cold weather we've been having.
When the car starts up, it doesn't run on its default operating settings. Instead, it's on an open-loop warm up program that is monitored by coolant temp, MAF, rpms, and throttle position. In short, it's trying to get the operating temperature up as fast as possible. It's also sucking gas fast, so I bet your mileage is going down. (At any throttle position during the winter, the air that is sucked in contains more molecules/sq in so the fuel ratio needs to be adjusted (upped) to compensate, or else the mixture leans out.) Still with me?
If there are codes, however, it could be a faulty O2 sensor, leaky manifold gasket, clogged throttle body, or bad TPS. But since you didn't mention the car throwing codes, so you probably don't have to worry about any of those.

Haha nice what she said. Oh and since when do most cars idle around 1k??

[lagos]

Pop the hood with the motor running at look around for anything hissing. It sounds like you have a cracked hose creating a vac leak and thats whats making your idle bounce.

[Erik]

alright. Ill do a propane test and let you know.

[DPancoast]

either that or brak kleen...or however the **** the spell it. Red bottle.

Also.. My car idles at 1500....should be at 850 LOL.

[95naSTA]

It's probably a bad or sticking IAC valve.
Is it a 3.1 MPFI?

[SovXietday]

Pull off the IACV and clean the screen. If that doesn't help look for a vacuum leak.

[lowbri21]

could be an evap charcoal canister clogged up seen the same thing happen to a 92 legacy