weird idle when i start my car (cold)

[S|b]

when i start my car (cold) the rpm raises to about 1500 rpm (like it should do) but then immediately drops down to 500 rpm and then raises to 1500 rpm again

the car does that about 2 times..then its a steady 1500 rpm

what is the problem?

/Stef

 

[hlweyl]

It's always a tough diagnosis when there is an erratic idle. My first questions would be 1) Are you getting a check engine light? if so, I would pull the codes, that would narrow it down a bit.
2) Has any work been done on the car lately?
3) Do you have any mods?

 

[Briank]

The 3 things I would try is first do a reset on the ecu, then do the idle bypass adjustment procedure and then clean the throttle body. If you are having problems after that you may what to change the fast idle valve.

 

[nsxexotic]

bleed your coolant as well.

 

[Larry Bastanza]

I am with Briank on this one, but would reverse steps 2 and 3. If the throttle body is dirty, you may mis-adjust the idle bypass, and have to repeat it.

Does this symptom happen if you come off throttle quickly, lets say into nuetral at a light??

HTH,
LarryB

 

[S|b]

It's always a tough diagnosis when there is an erratic idle. My first questions would be 1) Are you getting a check engine light? if so, I would pull the codes, that would narrow it down a bit.
2) Has any work been done on the car lately?
3) Do you have any mods?

1 no check engine light

2 no work has been done on the car

3 no mods except an exhaust and an open air filter (cleaned it some months ago)

/stef

 

[S|b]

I am with Briank on this one, but would reverse steps 2 and 3. If the throttle body is dirty, you may mis-adjust the idle bypass, and have to repeat it.

Does this symptom happen if you come off throttle quickly, lets say into nuetral at a light??

HTH,
LarryB

my car runs perfect when its cold and warm..its just that i have noticed this erratic idle the first 5-7 seconds when i start my car cold

/Stef

 

[NSX2398]

Mine has done this for a while .. but only dips once, not twice. I originally thought that I might have been letting the clutch out (in neutral) too fast and the extra drag was pulling down the idle. But recently, I've had my a/c off (auto but with a/c off) and I've noticed this week that it's not doing the dip any more. Try turning yours off just before shutting off the engine so that on the next cold start it will already be off. If it is causing the problem, I'm not sure if it's a bad thing or not. Maybe some of the guru's can tell us if the idle adjusts when the a/c compressor engages.