High Idle on 97 D90
Ok, now I am at my last straw with this. I have a 97 D90 with 126K. The engine was replaced with a 99 Disco engine at 65K. I just bought this D90 for cheap a few months back and am fixing everything on this both mechanically and cosmetically so I can sell it for a profit. This one was in bad shape when I got it and was not taken care of. The previous owner was running it with the end plate on the air filter (basically without the air filter). The engine wants to run at 1,500 to 2,000 rpm at idle. I have posted a few threads and have read a million about this problem and have replaced the oxygen sensors and the throttle position sensor with no change. I cleaned the throttle body and the stepper motor with throttle body cleaner last week and checked for leaks around everything and found none. With the stepper motor detached from the throttle body, I had my wife turn on the ignition, and the stepper motor moved in and out. When she turned it off, the piston moved out too far that I could not get the motor back in. I had her turn it back on again and I unplugged it while the piston was in. Once I got everything back together I started it up and I thought I had it fixed!!! The engine was running between 500 and 750 and would drop almost a little low. Things were great for a few days and I moved on to cosmetics on the vehicle. Yesterday the engine was idling high again so I repeated what I did last weekend and with the same result but the engine would stall once in a while. After turning the ignition on and off a few times, I was back to a high idle again.
Now for my questions: #1. If this has nothing to do with the stepper motor since it seems to move in and out ok, could it be the mass air flow sensor? If so, is there a way to clean it without damaging it (compressed air, throttle body cleaner, etc...)? #2. If it is the stepper motor, I have seen in a few threads that you can use a less expensive GM stepper motor instead. I have only seen these threads on 95 and newer, can this work for my 97 with a 99 Disco engine? If so which model and year GM vehicle? #3 Is there anyone in the Cincinnati area with a D90 or Disco willing to swap parts back and forth for an hour until I find the problem? #4 If my last resort is to have the computer reprogrammed, what is my cheapest route of doing this?
Sorry for such a long post, but I figured I would give as much info as possible. I really need to fix this so I can sell it, my wife is pregnant and growing larger every day!!!!
Thanks for any help you can give,