High Rev at Start up ?

[-EnVus-]

Any ideas to what may cause my 2002 Galant 2.4L to Rev around 2.5k rpm when started after sitting ? It will drop down to normal RPM after 1 min but it has never reved high like this before.

[kevint2]

If the vacuum hose to the brake booster came off the intake manifold, is cracked or broken, or if the brake booster has a bad diaphragm, it could certainly cause this condition. Not only would it cause your engine to rev up to pretty high RPMs, it would cause your brakes to function poorly and require a huge amount of effort to stop the vehicle. Look for a hose about 1/2 to 3/4 of and inch in diameter going from the intake manifold to a canister on the driver side of the engine compartment at the fire wall. Check to make sure it's connected at both ends and if it has any leaks or cracks.

This could also be caused by the throttle plate sticking open. Either due to a hung or stuck throttle cable, or mechanical damage. If the vehicle has cruise control (which I would assume it does), there is another cable involved in actuating the throttle that could be causing the problem. The cruise control stepper motor could also be stuck in one position.

There is also an item called an idle air control motor or solenoid (also known as an IAC) located near the throttle body which can often stick in position if internally, it catches "gunk" or "sludge"... Sometimes they have even been known to come apart due to wear. If it only does the revving when it's not in gear, this is a likely scenario depending on the position it may be stuck in.

[-EnVus-]

If the vacuum hose to the brake booster came off the intake manifold, is cracked or broken, or if the brake booster has a bad diaphragm, it could certainly cause this condition. Not only would it cause your engine to rev up to pretty high RPMs, it would cause your brakes to function poorly and require a huge amount of effort to stop the vehicle. Look for a hose about 1/2 to 3/4 of and inch in diameter going from the intake manifold to a canister on the driver side of the engine compartment at the fire wall. Check to make sure it's connected at both ends and if it has any leaks or cracks.

This could also be caused by the throttle plate sticking open. Either due to a hung or stuck throttle cable, or mechanical damage. If the vehicle has cruise control (which I would assume it does), there is another cable involved in actuating the throttle that could be causing the problem. The cruise control stepper motor could also be stuck in one position.

There is also an item called an idle air control motor or solenoid (also known as an IAC) located near the throttle body which can often stick in position if internally, it catches "gunk" or "sludge"... Sometimes they have even been known to come apart due to wear. If it only does the revving when it's not in gear, this is a likely scenario depending on the position it may be stuck in.

I checked the brake booster line and it is fine and the pedal feels good also. I sprayed some WD40 around the engine and hoses and it didnt change idle any so i assume it should be ok far as hose leaks. I cleaned and scrubbed the intake port and throttle valve today and it seem fine closes and opens all the way smooth. I will remove and check out the IACV tomorrow and see how that looks and it can be started in P or N and either way still does it. It just started this this past week never had issues before that.

[kevint2]

The IACV is likely where the problem,Its very hard to tell without seeing the engine and hearing it in person but it looks like you don't have a check engine light so its probably one of those little things that will be a pain in the ass to find but wont really hurt the motor in the end...If you need anymore help,just let me know

[-EnVus-]

Well my biggest worry is the car has 160k miles on it and dont need that kind of strain from high revving when cold.

[kevint2]

That is very true!

[CNH7207]

tps throttle position sensor may need to be cleaned or replaced