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View Full Version : Check engine light at start up 92 525i


japbike736
12-03-2009, 05:06 PM
New problem, My check engine light is staying on when I cold start in the morning. The engine fluxuates between 500 and 2000 RPM. Up and down, Up and down. I can shut it off and restart. This seems to stop it most of the time.....When it does not I go ahead and drive it, the light goes off and the engine runs normaly after a 1/4 mile or so.....Any Idea's...I did put a performance chip in it last summer......Could this be the problem???

nmp411
12-03-2009, 06:37 PM
Have you tried the stomp test?
I'd guess it is the o2 sensor.

japbike736
12-03-2009, 06:44 PM
stomp test??

yaofeng
12-03-2009, 07:46 PM
You have a vacuum leak somewhere.

nmp411
12-03-2009, 07:56 PM
stomp test??

http://www.bmw4life.com/stompTest.htm

You have a vacuum leak somewhere.

Actually, I switch my vote, I agree with yaofeng

japbike736
12-04-2009, 01:46 PM
Would a vacume leak only happen when the engine is cold?? After warming up it starts and runs as normal......

brians900@aol.c
12-05-2009, 07:13 AM
this is most likely your idle control valve, either one of the hoes is off or cracked creating a leak or the valve is sticking which can be cleaned or replaced.

jenlex
12-05-2009, 07:28 AM
this is most likely your idle control valve, either one of the hoes is off or cracked creating a leak or the valve is sticking which can be cleaned or replaced.

It probably is dirty inside use brakecleaner and check the hoses and then it must be ok.

Alex

japbike736
12-05-2009, 11:09 PM
The Bentley says on an M50 the valve can be replaced without removing the intake manifold. In another section it says the manifold is best removed to get to it. Witch is it?? Where is it and what does it look like?? It also talks about a buzzing sound while the car is running?? any suggestions?? I would rather not remove the manifold.....

jenlex
12-11-2009, 03:15 PM
It is on the left side off the engine and then more to the back.It makes a buzzing sound indeed and if it looks the same as on an M60 engine a round shaped metal coloured with a connector on it.

Alex

cpnwrench
12-24-2009, 12:55 PM
:smokin:

Hey japbike,
You probably got a lot of info here as to problem.

Yaofeng has good info on the M50 motor and its quirks. I would agree as to vacuum leak. most of the hoses around the intake manifold might look ok, but you actually have to squeeze, bend and/or twist some of them to really see where they may be cracked or split, I have same car as you and found several hoses in this condition, so i replaced them. (also check that big fat hose from air-box to throttle body, notorious for being cracked underneath). Another check would be the stomp test.....this involves turning the car "on" not start it and in a five second period press the accel pedal down five times fast to the floor... then the check engine light will flash in a sequence which relates to codes pointing to what possibly could be the problem. (Hope you got your hands on a Bentley manual).

Also the relay problem is more than likely culprit when it comes to doors and locks etc. although you say after it warms it seems ok.. this leads me to believe a short or an intermittent open in the wiring harness somewhere from the relay location. PIA to multi-meter that stuff out, but if you have the time and the energy you can track it down. (again, the Bentley has good schematics for this).

best of luck and Merry Christmas!

cpnwrench

:smokin:

supertech777
12-24-2009, 04:26 PM
I believe it could be your oxygen sensor it is getting weak especially during initial start up when a rush of unburned
fuel is going through it . because that is how the engine reacts when the O2 sensor is disconnected in order to get an actual reading of the emissions . imo

jbh1989
12-25-2009, 10:40 PM
I believe it could be your oxygen sensor it is getting weak especially during initial start up when a rush of unburned
fuel is going through it . because that is how the engine reacts when the O2 sensor is disconnected in order to get an actual reading of the emissions . imo

The oxygen sensor is ignored at startup, it hasn't gotten hot enough to go into closed loop. It'll ignore the O2S when cold.

When is the O2 disconnected to get an actual emissions measurement?

In order for the check engine light to be illuminated, you'd need to have an actual electrical problem. Either an open or shorted circuit or actuator. Without knowing the code it is setting it's hard to suggest what might be the problem. You could have a skewed coolant temp sensor or at least a sticking one. Do the stomp test and we can narrow it down more.

If it only does it cold, it could be something that is compensated for by the oxygen sensor once it reaches closed loop (which won't take a long time). That could be an air leak but I don't believe the MIL will illuminate on a lean code dead cold 1) because it doesn't know--the O2 hasn't warmed up 2) because the diagnostics are mainly electrical on that vintage of a vehicle. Like I said, get the code and we can work from there. We can do it without but it'll be a lot of work and tailchasing. Do a lookover of the engine compartment, make sure everything is connected securely.

PS sorry to be jumping in all these threads on my first day. I've been lurking and finally got enough motivation to register.

attack eagle
12-29-2009, 01:08 AM
Sounds like a TPS issue to me.

You can run with NO 02 connected (hell no exhaust) and not get those issues.

Onlything I have ever seen that would give issues like that is vacuum leak, particualrly a cracked FPR hose, majorly cracked TB elbow, and/ and IAC TPS going out... or a combo of all 3.

If the IAC is going out of efective range because of metering leaks+ vacuum leaks, that would sure as hell do it.