My 2007 BMW 328i looses power and idles rough when warm

[memjess]

My 2007 BMW 328i runs perfectly when cold. Once when heat up, it looses power and idles rough. What I have thought of and done is to replace the coolant temperature sensor, plugs and oil packs, air mass meter. I’ll appreciate any good idea.

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[Manolito]

A 2007 should set a code for just about anything that would cause the car to run noticeably rough. The code might not point to the true problem, but some code should set. The fact that it is running badly and not setting any codes is the biggest clue here.

Normally when a car runs OK when in cold rich mode, but goes bad when it tries to go closed loop, we look for things that interfere with closed loop operation, which is what you have done, temperature sensor, MAF sensor, oxygen sensors, and most importantly and common - air leaks. Air leaks, however, will cause one of two things - power loss OR rough idle, depending on where the leak is. That fact that you have both symptoms points away from an air leak.

I suspect that you have a problem in the wiring harness to the DME, or a failed DME. The older models had a serious problem with water getting in to their DMEs. Hopefully BMW has corrected that by now. Do all the warning lights illuminate properly when you turn the key to the On position?

One last thing, has anyone done any work that that might have touched the throttle plate? It is really easy to knock those drive-by-wire throttle plates out of calibration. Your symptoms don't really match that problem, but it is a problem that the computer might not understand, so who knows how it might react.

[David Mc]

Which coolant temperature sensor did you replace, the double temperature switch on the right hand side of the cylinder head (part 13621703993), or the one on the side of the radiator (part 61318363677)?