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      12-07-2023, 08:07 AM   #1
wigwig
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Engine Surge on cold start

I have a 2003 z4 3.0i, it runs great when itís warm out, but Iíve noticed as the weather has been getting colder that it idles a little rougher than normal. Today was the coldest day weíve had so far (30F) and it completely died out on me. It had some trouble starting (which Iíve experienced more and more recently) but seemed fine once it got there, but while I was driving down the road at ~30mph the engine completely shut off, and when I tried to start it again the RPMs surged up and down and there was no throttle response. What can cause this? It also threw up a few codes that Iíll attach along with the freeze frame, but I am new in the car scene not familiar enough with how this engine works to be able to figure out whatís wrong.
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      12-07-2023, 06:26 PM   #2
JAS1169
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The stored stuff may be old. The pending codes are being caused by your issue.

I'm guessing this is your problem. please see attached video:

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      12-08-2023, 08:26 AM   #3
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Quote:
Originally Posted by JAS1169 View Post
The stored stuff may be old. The pending codes are being caused by your issue.

I'm guessing this is your problem. please see attached video:

https://www.youtube.com/watch?v=AgMFHaRhRdI
Iíve already cleaned the IAC valve and the throttle body, neither of which seemed to do anything about the problem, and the codes were not there until the engine died on me. The main thing that is putting me off is that it only every has problems when itís cold outside (<50F), and runs perfectly normal when itís warm. Iím going to check on and clean out all the electrical contacts to and from the ECU when I get home from work tonight.
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      12-11-2023, 11:09 AM   #4
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Use ista+ and follow the test plan for the error(s).
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      12-11-2023, 11:32 PM   #5
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Last year my GM5 started going out with the hot weather. As it got hotter it (the door locks) got worse. The site of the vendor I sent it to for repair noted hot/cold weather can cause the door issue to get worse. When I finally pulled the GM5 the passenger door would no longer unlock.
The GM5 is a small computer which controls the locks and a few other things on the car. The GM5 is tied into main computer. I'm guessing (and only guessing) that the main computer may also be affected by cold/hot temp's if they are starting to fail.
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