Hey guys. Need some advice on where to start looking to fix an issue with port motor. It's an 2008 6.2 and has been doing this since new. When the motor is up to running temp and is slowed down to idle the rpm's don't want to come all the way down to 650 or so, but stick up around 1100. If the throttle is quickly bumped up and back the rpm's will normally settle down. I recently drilled two 1/8th holes in the t-stats and replaced the rotor and cap of the distributor... on the test ride the motor would not idle down from 1100 rpm's and had to be shut down. With the t-stat drilled port motor ( only drilled the port side) is way cooler than the starboard motor. Any ideas on what to check?

Idle Air Control valve sticking.

If motor does not come up to temp the ecm will keep idle up high & rich

Turbo, so drilling the T-stats was mistake?? or faultly iac valve? I guess "up to temp" wouldn't be 160 because at start-up on cold motors they would idle down before that I would guess. I'll look into checking the valve. Thanks for the comeback.

Austin, did you gain any rpm with the motor changes you talked about doing awhile back?

I just put the new rotor and caps on but haven't opened her up yet to see. My old ones were corroded so it's got to be somewhat better than it was. It would be great to see 6mph , like the poster who had the tip got, but I'm not counting on it. I'll post after testing.

No need to drill the tstats on 6.2's. You shouldn't need to. Running it too cool will screw with the ecm's. I agree, probably an IAC.

Already drilled the t-stat on one. My washout water hose has low pressure, drilling that tstat helped it to not overheat while on the hose.