High idle when I start my car?

[JEDI]

i have a 2002 chevy prizm. in the past when i start my car, my engine is at 1600 rpm. today in the afternoon, i noticed it was 2000 rpm. The temp this afternoon was 50 F.

Is this normal? If not, what could be wrong? (yes, i took it to the dealer a couple of weeks ago because my gas milage went from 32mpg to 25mpg. they said diagostics reported everything normal, and have no idea why my milage dropped 20%. it's been like that for 2 months )

so if i take it back to the dealer, and they still say the diags check ok, what could i tell them to check? (for both the high idle and gas milage problems)

 

[JeffreyLebowski]

check compression, clogged fuel line, idle, may just need adjusting.

 

[WinkOsmosis]

My 240sx decides what it idles at. Sometimes it changes on its own at a light, with the AC off or on, it always fluctuates between 600 rpm and 1000 rpm. Sometimes 1500 when I start.

 

[JeffreyLebowski]

Originally posted by: Jellomancer
My 240sx decides what it idles at. Sometimes it changes on its own at a light, with the AC off or on, it always fluctuates between 600 rpm and 1000 rpm. Sometimes 1500 when I start.

OK, so i'm not the only one. lol

What year is yours?

 

[Vortex22]

While were on the topic of idling...

Is it normal for my Civic to idle at 500-600 rpm? It seems kinda low.
I'm in Florida btw, so it's almost always hot outside. It idles around 1000 when it's colder.

 

[blahblah99]

Does your have a mass air flow sensor or a MAP sensor? You could have leaky injectors, bad intake manifold gasket(s), leaky throttle body/plate, or bad idle air valve. The point is air might be leaking into your car at idle when it's not supposed to and that'll cause the engine to idle a little higher than it should. It could also be a bad coolant temperature sensor or the plug could be corroded and not make contact.

As for the problems with 240s, I know all models have notorious problems with the MAF sensor going haywire... so you guys might look into that.

 

[Pepsi90919]

the computer ultimately decides what it wants to idle at.

when the engine's cold the idle will naturally be higher because the computer wants the engine to be hot.

when the engine's hot there's no need to idle it as fast.



when i restart my civic's engine when it's hot it idles high for 2-3 seconds (initialization) then drops like a rock under 1000 rpm.

 

[ThisIsMatt]

Originally posted by: Vortex22
While were on the topic of idling...

Is it normal for my Civic to idle at 500-600 rpm? It seems kinda low.
I'm in Florida btw, so it's almost always hot outside. It idles around 1000 when it's colder.

That's perfectly normal...shows your engine is in good shape somewhat My accord idles at the same rpms, except when I start it after sitting for a while and the auto choke is on...

 

[boyRacer]

blip the throttle...