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Running rough on cold start

Discussion in 'E36 (1992-1999)' started by 391075, May 4, 2011.

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    My 1995 325IS ramdomly runs rough on cold starts. It seems to only occur following a short engine run/driving time on the prior start. Any ideas on a diagnosis and solution to the problem will be much appreciated.

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    Rough idle on cold start

    I have the same experience with my 1998 Z3 2.8. very short running times seem to cause the symptom. Not shure what can be done to correct it. It clears up okay after driving for a mile or so. :rolleyes:
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    From what I know from driving my 1995 325is now with 256K is that they dump a lot of gas into the engine when you start it cold. Make sure you let it run for a few minutes before turning it off. I discovered this one morning when I just moved the car and then shut it off.
    Hope that helps.
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    • Technical Service Advisor


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    That is correct that on short run times the engine does not have enough time to get into closed loop. So like mentioned above when the vehicle first starts cold it uses a lot of fuel because the O2 sensors are not up to proper operating temperature they are not used to control the amount of fuel injected (called open loop). Instead it is ran off a program inside the DME (digital motor electronics) the program is called a fuel characteristic map from engine coolant temperature and MAF/IAT readings. Once the engine is warmed up and the O2's are at a operating temp then the DME switches to closed loop and uses the O2 sensors reading to adjust fuel injection amounts. When the vehicle is not allowed to warm up to closed loop and is shut off right away you are basically slightly flooding the engine causing a rough run the next start up until it can burn off the extra fuel.
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    Raphaellacerda 98 318i “why don’t I have a steering tilt?”

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    Still having the cold start issue ? For me ended up needing a new coil pack
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    Thank you for your reply but I sold the E36 this past November. The problem does not seem to occur on my current BMW(s) (E61,E93,E83).

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