2001 Challenger 1800 240 EFI M2 Gen 1 high Idle when warm

[1800 Challenger 01]

Hello,

I have a 2001 Challenger 1800 240 EFI M2 Gen 1.

When I start the engine cold, it idles at 1100 RPM (as specs).
After running it for a while and getting the engine warm, when I reduce the throttle to idle, it idles really high around 1800 - 2000.
Even if I shutdown the engine for 10-15 minutes (engine still warm) and then trying to start it again, the idle is still high.

Any ideas what this means? I am sure this shouldn't be normal.

 

[ripcuda]

Hi. Agreed, not normal (I have same engine). Things I would check

• Is the throttle binding? Is it hanging open when warm? Is it returning to idle position? I would check this at the throttle linkage on the engine (lower port side - below VST)
• The port cylinder head temp sensor. It ties into the TPS and the signal to the ECU for fueling. If this is bad, I could see it acting up when warm.
• TPS. I'd check it's volts across the throttle range to ensure it's not going flakey. Then check again when warm. (Admittedly this isn't very easy to do)
• Check your battery voltage when running cold (idling normal) and when hot (idling high).

This is where I'd start. Cheers!

 

[1800 Challenger 01]

Thanks Ripcuda,

I think I can perform these tests, but they require going to the lake. Hoping the weather permits one more trip.
Only thing I didn't understand is the meaning of "throttle binding".

Really appreciate the help. If anything else I should do, please let me know.

 

[Tim75]

Thanks Ripcuda,

I think I can perform these tests, but they require going to the lake. Hoping the weather permits one more trip.
Only thing I didn't understand is the meaning of "throttle binding".

Really appreciate the help. If anything else I should do, please let me know.

Throttle binding is anything that prevents free motion of the throttle.

Another thing to check is the bleed system. That is the system of small black hoses that run around the forward half of the engine. These hoses route pooled fuel inside the engine to the fuel-air flow where it will be burned. A break in one of these hoses can cause a vacuum leak and fuel-air imbalance and a high idle. After all- those hoses are 20+ years old.

Also check that the timing trigger is returning to its idle position. It could also cause high idle. It is under the flywheel, but visible. There is a 6 wire harness coming from it. Starboard side.