Okay...I've been having idling problems since I purchased the truck about 3 weeks ago and I've done numerous maintenance and repairs to make the truck run good. Recently, I had all the gunk cleaned out of the vacuum hoses and pcv valve and my MAF was replaced. The car idles fine now. Actually, it's been idling the best since I've purchased it. I had the CEL w/ code 48 reset and its been off for about 4 days now - longest time period it has been off. Prior to changing the MAF and cleaning the vacuum hoses, the CEL would turn on after 5 hours of driving.

I do notice one thing... everytime the CEL w/code 48 comes on is when I'm parking. Going from drive to reverse, etc... Like all older rovers with high mileage, I get the infamous loud clunck from drive to reverse and park to reverse. When I shift from drive to reverse or park to reverse, the rpm drops to about .500 and stays there until I shift out of the reverse gear. After a few shifts to park the truck, the CEL comes on. I suppose the CEL is being triggered when shifting into reverse because the idle is trying to find the right "idle". I'm probably on the right path, but I have no idea what else to do! This CEL is driving me up the wall.

I can reset it and drive it for a few days and the CEL will stay off as long as I pull into a parking spot. But once I parallel park, the CEL is almost guaranteed to turn on. Is there some sort of sensor I should be looking into that may be causing this? Below are some of the things I've repaired/changed since I've purchased the truck. Thanks in advance.

Stepper motor
MAF
Spark plugs and wires
steering gear box
2 motor mounts
Intake manifold gasket
valve cover gasket/grommet
Upper Radiator hose
Lower radiator ose
Rear passenger calipers
Front brake pads
Front brake rotors
Rear brake pads
Oil pan gasket
Brake fluid flush
Intake manifold plenum - upper
Changed rear end oil