I have a 2007 Mini Cooper. It keeps throwing code P1638 on my code reader on these really really cold mornings, and the engine seems to search for idle, reving betwween 500RPM and 1400RPM. The car runs fine after it warms up, I clear the code and restart the engine.
What is wrong, and what should I do to fix this permanently?
P1638 throttle stuck what happens is that some debris got on the throttle body near the throttle plate. The throttle plate motor is drawing more current from the computer than it's designed to. It is drawing more current than needed to move the throttle plate. It's not designed to move debris or gunk if it encounters an obstruction and can't close for a few milliseconds it will throw the code.
I had this problem on my R56 MINI Cooper. What I did was use some lubricant spray oil into the pipe that connects to the throttle body to the valve cover. Then start the engine at idle and spray a few sprays of that lube into the PCV until you hear the engine rev up a little. Then put pipe back on and rev your engine a few tines so the throttle plate moves around a little bit. Then do this over again one time, then clear the code using scan tool code should not come back.
If it comes back then you need to do this again a few times or turn car off disconnect battery and take off the air hose to throttle and spray lube oil directly on throttle plate and body. While at it, clean with a rag then re-assemble. Start car also, then turn car off and unplug MAF. Then plug back in the connector to make sure it's secure. Start car and code should not return.
I'd try squirting some WD40 into the throttle body assembly first, before considering replacing it.
As Paulster2 said, sometimes the body gets gummed up or, in your case, stuck from cold - WD40 will help lubricate the body and save you some money.
I've used this trick a fair bit, and usually do it once during my own mini service of oil and filter change - so every 6ish months, and never had a problem.
Does it ever stall out completely? The code doesn't make sense, but the symptoms match what I experienced when my high-pressure fuel pump was failing. If you have an OBD tool, you should check the fuel pressure.
See my question and answer: The Mystery of the Misfiring MINI
P1638's code is: Throttle Valve Position Control; Throttle Stuck Temporarily ... since I don't know a lot about the Mini Cooper, generally I'd say the motor for your throttle position control is sticking due to freezing or age (gummed up). This should be a user replaceable item (mechanic not needed unless you are a complete mechanical nightmare), just ensure you are getting the correct one for your application. It appears each different engine type uses a different type (or at least a different part number) for the throttle body. Partsgeek.com has them.
