Cold start, engine choking

[Z4@Phuket]

Still unsolved for my 23i
Every morning when I started the engine, the engine start to choke, engine RPM is not stable (running between 800-1,000 rpm) , If I drove off immediately, the car will dance like someone is choking. If I let the engine warm up for a few minutes, no problem.
Went to BMW service 2 times, no fault in the computer, increase the idle PRM from 600 to 800 RPM, still unsolved

Anybody can help, I suspected fuel pump issue??

[mcbeee]

Let it warm up for a couple of minutes anyway, it gets the oil circulating and prolongs the life of the engine. In perspective...How well do you function the second you wake up ??? As for running rough...no answer there, mine is pretty smooth (not a 2.3 though).

[Silver-Bolt]

Software more likely. At cold start the computer is supposed to feed in a little more fuel. Sounds like your may be running lean. increasing the idle is not the answer.

[GEARS5]

My 3.5i takes a long time to turn over, then when it does it chokes until I give it some gas. Had the HPFP replaced last month. Each time I start it, I keep my fingers crossed that it will. Taking back to dealer again next week to check out..... among other things. Also Check Engine light just came on.

My 6th BMW and the most problematic of all of them.

[msimon18]

Do not have to worry about that down here. There is NEVER a cold start as the temps are in the 90's most of the time !!

[mcbeee]

Originally Posted by msimon18

Do not have to worry about that down here. There is NEVER a cold start as the temps are in the 90's most of the time !!

So it's a DAMP start then......I was waiting for a smart comment from someone in the tropics

[Dr Stig 2]

Report from the Tropics...

My 35is is taking forever to start.
Damn thing wont be ready for delivery for another week or so!
Arghhh!

[teagueAMX]

Originally Posted by Z4@Phuket

Still unsolved for my 23i
Every morning when I started the engine, the engine start to choke, engine RPM is not stable (running between 800-1,000 rpm) , If I drove off immediately, the car will dance like someone is choking. If I let the engine warm up for a few minutes, no problem.
Went to BMW service 2 times, no fault in the computer, increase the idle PRM from 600 to 800 RPM, still unsolved

Anybody can help, I suspected fuel pump issue??

Fuel pumps are more consistent then that. The HPFP problem confuses the issue for everyone because on the 35i there are two pumps. They aren't backup pumps but they act that way. Your 23i only has one pump in the tank so when it goes out your car won't start at all.

Modern computer controlled cars have a bunch of sensors to feed operating and driving conditions to the ECU. They are responsible for reading temperature, humidity, altitude, fuel octane, engine speed, car speed, accelerator pedal position, break pedal position, etc. When you start for the first time the sensors tell the computer the engine is cold and the air is dense. The computer alters the ignition timing, VANOS, fuel charge, making it a bit richer to compensate for the dense air (ratio of 14:1). As the engine warms up the air intake is warmer as well, the air is less dense and all those changes are reversed.

In your case there could be a number of problems:

1. A bad fuel injector that will make it stumble or "choke". When the engine is cold the computer may not be able to overcome a fuel injector that's injecting too much gas. As the engine warms up it’s better able to compensate. On the other hand, if the injector is weak, it may not be injecting enough gas and the engine is running lean when it’s cold.
2. A weak/bad sensor and or sensor module sending misleading information to the ECU. As noted above this would affect fuel mixture, ignition timing, etc.
3. A vacuum leak. Again, as the engine warms up it’s better able to compensate.
4. If your engine is equipped with an air mass sensor, that may be not working properly
5. Fuel pressure regulator not functioning properly when the engine is cold
6. VANOS not working properly – may be related to above
7. Faulty ECU (main computer)
8. 8. Software – needs a re-flash

These are just a few things to look for or mention to SA. They all affect the engine management system which with a computer controlled car is a big deal. Keep in mind the issues I mentioned above typically throw error codes when there’s a fault so when they say there’s no codes they automatically assume the computer is looking at each of these things and don’t bother looking themselves or running diagnostics.

Don’t be surprised when they act like you’re ignorant and may even suggest that you leave it to professionals. Had they adequately diagnosed and repaired your car we wouldn’t be having this conversation, right! So, don’t let them bulldoze you. It is not normal for your car to run rough when cold – maybe in the 1940’s but not in 2010! Don't let them push you out of the place without a copy of the actual diagnostic sheet!

[msimon18]

Yup, no issue starting. Mine just stalls every time I stop at a light !! Seems there is a software fix for this that seems to break something else !!! typical BMW !!!

[teagueAMX]

Originally Posted by msimon18

Yup, no issue starting. Mine just stalls every time I stop at a light !! Seems there is a software fix for this that seems to break something else !!! typical BMW !!!

Don't mean to laugh but your sarcasm is funny. I suppose it might be funny to you if didn't hurt so bad!

I suppose we don't want them to apply the same software fix to Z4@Phuket car to solve the choking in the morning problem?

[Z4@Phuket]

Thanks for all comments
I am waiting for BMW to give me the answer