2000 OW 2.5 litre MT- idle problem/power loss

[wvcaver]

Ok, I have a 2000 Outback Wagon, 2.5 litre with a manual transmission and 200k miles. The engine was replaced with a used engine back at 130k, and the current engine has 156k on it now. For the past year and a half or so, the car has idled excessively high (seemingly correlated with humidity, initially, but always present now), around 3000 rpms. This has caused me to wear out a clutch in short order, as well as given my fuel mileage a serious hit. In trouble shooting, we have done the following: replaced the fuel filter, replaced the computer (with another used one), replaced the front upstream O2 sensor, replaced the air filter, replaced the spark plugs, replaced the coil pack, replaced the throttle body and all sensors. The car will also hiccup on long uphills at interstate speeds, stopping once I let off on the accelerator. Also, I find this interesting: I start the car. It is idling around 3000 or so. I press the clutch in (and keep it pressed in for the duration of this experiment). I shift from 1st to neutral (the clutch remains pushed down). The rpms drop. I move the shifter to 2nd. The rpms increase. I move it back to neutral. The rpms drop. This makes no sense to me, as the clutch is depressed THE ENTIRE TIME. I've tested this several times, and it is consistent. Help is appreciated, and I will post the results of what is going on, as the car is currently in the garage, torn apart, getting a new driveshaft (bad u-joints) and timing belt, so I am open to suggestions on what to try while I have it opened up.

 

Thanks, and I look forward for some help!!

 

~clayton

[Legacy777]

bump

[Gloyale]

Sounds like the IAC is stuck wide open.

 

Have it tested. IDK, you might be able to simply block it off to see if the idle drops.

 

Also, you may want to test the MAP sensor.....or just try swapping a different one on.

 

A bad MAP would also explain the highway hiccup.