2000 Grand Prix, high idle or normal?

[GT2000]

The 2000 Grand Prix GT I got recently has a high idle in my opinion, when it's first start after cooled down completely, like when it sits overnight. The idle is normally around 1700 RPM's. The idle comes back down then after 30 sec, maybe a little less. The reason I think its a little weird is because my brother has 1998 grand Prix and even on the coldest days it really doesn't go above 1250 RPM's. Also whats weird too is that it doesn't have to be cold outside either like 70-80 degrees it will still do it. Kinda afraid to see what it will do when it's 20 degrees out. Now when its warmed up or even a little warm it's totally normal. The only reason I'm asking is because the other Grand Prix doesn't do this. What do you guys think?

 

[Scottydoggs]

you could have a bad ait sensor, that little one in the intake tube, try cleaning it. it might be telling the pcm its super cold out when its not. its a cheap one to replace, like 12 bucks. its pig tail could also be bad. look for cracks or missing insulation.

the check engine light on?

 

[GT2000]

you could have a bad ait sensor, that little one in the intake tube, try cleaning it. it might be telling the pcm its super cold out when its not. its a cheap one to replace, like 12 bucks. its pig tail could also be bad. look for cracks or missing insulation.

the check engine light on?

No engine light and I checked and no code either.

Is it the little one on the right there

 

[Scottydoggs]

far right in the pic not labeled. it pulls right out the tube, no tricks.

 

[GT2000]

Ok i'll check into it and i guess just replace it, ill try and clean it first

 

[Scottydoggs]

brake cleaner and a rag, theres not much to clean, just the butt end of it. could be covered up in carbon.

 

[GT2000]

brake cleaner and a rag, theres not much to clean, just the butt end of it. could be covered up in carbon.

Ok thanks, I'll try that and see what happens

 

[Fivefingerdeathpunch]

A scan tool would make quick work on the IAT part. If the intake temp cold matched the ambient temps, the it's working just fine.

 

[GT2000]

brake cleaner and a rag, theres not much to clean, just the butt end of it. could be covered up in carbon.

I bought a new one and just started it and no improvement, and its around 55 degrees, any other ideas

 

[Scottydoggs]

did you say you cleaned the tb yet?

 

[GT2000]

did you say you cleaned the tb yet?

No i didn't......I noticed there's like a screen on throttle body, does that come off to clean it??

 

[Scottydoggs]

its got a snap ring in front of it. try not to damage it. its best to buy a new gasket and take it off and clean it, the back side is what is caked with carbon. tps might be dirty as well.

 

[GT2000]

its got a snap ring in front of it. try not to damage it. its best to buy a new gasket and take it off and clean it, the back side is what is caked with carbon. tps might be dirty as well.

Ok, if it's not at all dirty then what would I have to do next?

 

[Scottydoggs]

its dirty as hell trust me on that, but it might not be the issue in the end. dbw tb's are far more sensitive to the carbon build up.

have you tried pulling on the tb where the cables hook up? maybe its a cable going bad or bent cable bracket. pull the lever back to make sure its not being held open some.

all shots in the dark really. the cold start set up is in the tune, being we have no choke it over fuels when cold to keep it running. like it will command a afr of 13.0 for 30 seconds when its under so many degrees out. works its way from a rich af to normal over a minutes time as the engine warms up. depending on how cold it is. it being rich is why the high idle.

 

[GT2000]

Cant be held open, the high idle goes away, The problem is its not very cold outside and it does it eveytime. Can be 70 degrees and still. Then when you start it warm its totally fine, so confused why the air temp sensor didnt fix it

 

[Fivefingerdeathpunch]

Doubful the IAT was ever bad nor was it ever a problem.

Without seeing a data log it's hard to guess at a reason though it's seems hard to pinpoint on this one.

Start up idle asks for 1200rpm all the way up 90ish degree coolant temp but what I can't see are the tables not inlcuded in HP Tuners. There are very limited tables to see what other start factors are in place to determine start up airflow and idle air control valve controls on first start up.

The 2002 grand prix we have I know hits at least 1,500rpm on start up and then drops to 1000-1100 slowly then down to 750 after 110-120 degree coolant temps.

 

[GT2000]

Doubful the IAT was ever bad nor was it ever a problem.

Without seeing a data log it's hard to guess at a reason though it's seems hard to pinpoint on this one.

Start up idle asks for 1200rpm all the way up 90ish degree coolant temp but what I can't see are the tables not inlcuded in HP Tuners. There are very limited tables to see what other start factors are in place to determine start up airflow and idle air control valve controls on first start up.

The 2002 grand prix we have I know hits at least 1,500rpm on start up and then drops to 1000-1100 slowly then down to 750 after 110-120 degree coolant temps.

Mine is a 2000 but maybe thats what is suppose to do idk. I figured that sensor was the problem

 

[GT2000]

One thing i noticed on start up is i start it and it goes to around 1400 or so for like 2 second and then goes up to 1700.

 

[GT2000]

Do you think i should just live with it, it wont hurt anything right

 

[Regval]

My 2 cents: Check the throttle cable connection at the throttle body. The cable has an adjustment and the cable may be keeping your throttle plate open which would cause a high idle, similar to keeping your foot on the gas pedal.