RPM fluxuation?

[eversio11]

Hey there, I was having some problems with my engine lately. Just sitting in park, the RPMs would flux between 300-1000, then as it got close to stalling, would skyrocket to about 2500 RPM. Repeat. Sometimes it would go to the point of flat out stalling, especially when I went from drive to park.

I'm thinking the engine is not getting the fuel it needs, but I'm really lost. I tried to short out the engine lights but nothing came up, and the service engine light never comes on. Anyone have any thoughts?

[slusmiles]

It's a good possibility one or more of your fuel injectors need to be replaced. Does it idol rough?

[Slade901]

First, it would help if we know what kind of vehicle, year, model, engine type, etc. Put it in your signature.

Anyway, the two possibly candidate is the IAC (Idle Air Control solenoid) $29 and the second one is the TPS (Throttle Position Sensor) $19.

I would take out the IAC and clean it with a throttle body cleaner and use some brush to clean it. Clean the spot where the IAC goes in the throttle body. Test it to see if the IDLE is stable. If not, IAC maybe bad.

The TPS is known to cause that problem too. The TPS has a minimum voltage that it sends to the computer when it is IDLE and at WOT (Wide Open Throttle). If the TPS is bad and giving very low voltage past the IDLE minimum voltage then the RPM would go down and if the TPS gives out more voltage while at IDLE then the RPM would sky high. The TPS can't be cleaned and you just have to replace it.

Don't forget to check for some leaking vacuum. Spray some throttle body cleaner around the intake manifold and around the throttle body and the IDLE will change if you find a leaking vacuum.

[Cutlass Lover]

You know it is possible that there might be some ari bubbles in the fuel lines. That happened to my brother in his car after he rebuilt the engine. But since we don't know the specs about your car it could be a lot of things.