Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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?

share|improve this question

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.

share|improve this answer
+1 Old school FTW! – Juann Strauss Feb 14 '14 at 11:29
I can't believe I didn't mention this, but I have the S model. Is the throttle body a nightmare to get to if you have the S model? I have been assuming it would be, but haven't actually looked (been too cold in the North East to do anything outside). Also, isn't it odd that the engine can be revved while it's throwing a "stuck" code? What's with that? It only goes away after the engine is warm; restarting before warm you'll still have the idle searching problem. – Bob Feb 14 '14 at 17:24
Well, it's just gummed up from cold and maybe dirt. The WD40 trick along with cleaning will help. If you notice that the issue is happening every week or month, replace the throttle body (keep the old one, it's probably still good!) – Nick Feb 14 '14 at 18:53

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. has them.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.