I have a GT V6 Eclipse. Bolt on Weapon R Short Ram. a Noisy Cannon Muffler. and I recently replaced the thermostat in the cooling system.
The problem that I am having is that while the engine is idling, it rolls up to 9000 RPMs and then down to 4000 RPMs. It does not seem to affect the car -- merely annoy the heck out of me!!!
Thank you in advance for your advice.

 

well i dont think you motor will rev up to 9k but its probably from 900 to 400 and flucating, its probably your idle air control that might be going bad.

 

Any cel's?

 

Now the idle is worse and finally a CEL has come on...

P0455 came up twice...
The PCM has determined that a large leak exists in the evaporative emission control system

I have not gone under the engine to see where the leak may be coming out-- looking for loose bolts etc.

I appreciate any input you might have. THanks.

 

Sounds like a vac line or EGR type leak...

 

another problem could be that the evaporative emission control system valve is stuck open.

 

Agreed. If the problem started when intake was installed chances are maybe somewhere in that area

 

I misunderstood it to mean that there might be a leak in the exhaust...
Are there any tricks to finding an EGR (what does this stand for?) leak?
Or a Vacuum line leak?
thanks,