Author Topic: Will only rev to 2,500 RPM when hot (Fixed)� (Read 4589 times)

sgoldtho · « **on:** July 10, 2008, 06:03:50 PM »

I have 1990 E30 - 318iS that will only rev to 2,500 RPM when hot�

Symptom:
The engine starts normally and runs perfectly when cold, after about fifteen minutes of driving the engine as reached operating temperature, at this point the engine will not rev past 2,500 RPM.

Progress:
Fault code scan reveals a Camshaft Sensor error.

The Camshaft Sensor has been replaced with an after market unit from Pelican Parts (Part NO 12-14-1-721-861-M85).

Results:
No change to the symptoms.

Has anyone had this problem, or shed any light on what could be causing it?

Also does anyone know if the after market sensor is compatible with an Australian spec E30/M42?

Thanks
Steve

dwf08 · « **Reply #1 on:** August 12, 2008, 07:03:34 PM »

i had a prob kinda like this but would only go to like 3,000 then i changed the fuel pump and it fixed it. when you let it warm up and it starts doing that if you put it to the floor does it not just want to go?? thats wat mine did.

sgoldtho · « **Reply #2 on:** August 25, 2008, 06:40:22 PM »

Firstly:
Thanks dwf08 for your suggestion, I�m not sure if it�s the fuel pump on mine though. When the engine is cold everything is fine but when operating temperature is reached that�s when the problem starts, wouldn�t the fuel pump affect both hot and cold running?

It doesn�t make any difference whether the engine is under load or free revving it will not rev past 2,500 RPM. I�m guessing that the Engine Control Unit changes it�s mode of operation when the engine reaches a particular temperature.

Progress:
Had the Engine Control Unit and the Airflow Meter tested, all okay�

Checked the wiring from the Camshaft Sensor to the ECU all okay�

Much head scratching and staring blankly at the car wondering what the heck else it could be, I noticed that a couple of the plug leads had cracks in them near the camshaft cover. If nothing else they needed to be replaced.

Results:
Changed the plug leads, now the car runs fine both hot and cold.

Questions:
Does anyone have or now where I can find a description of what changes with the ECU when operating temperature is reached?

Does anyone have any theories on how cracked plug leads (probably arcing) could fool the ECU into thinking that the Camshaft Sensor pulse was missing?

Lastly is the Camshaft Sensor pulse only needed when the engine has reached operating temperature?

Thanks
Steve

christophbmw · « **Reply #3 on:** August 26, 2008, 02:55:14 PM »

...cam timing? if its off by a mere 6 degrees it will not rev past 2500 rpm and throw cam sensor codes. Also; what brand sensor did you use, most aftermarket ones are junk. How many miles? maybe you need to do a chain tensioner and chain? i would check the cam timing first though.

christophbmw · « **Reply #4 on:** August 26, 2008, 02:57:45 PM »

...just thought, maybe the arc from the plug leads was interfering with the cam sensor, i do know the the sensor has shielded wire so interference would effect it (highly unlikly though).

roelpeeters · « **Reply #5 on:** August 27, 2008, 08:28:10 AM »

I had a similar problem with on sparkplug lead, when cold everything was fine, when it heated up it started misfiring badly.

I think in your case a similar thing happened only it started interfering with your camshaft sensor.

The best solution is just to ditch your leads and go C.O.P.

sgoldtho · « **Reply #6 on:** September 29, 2008, 03:08:31 AM »

Thank you everyone for your help,

Since replacing the plug leads the car has been running perfectly for several weeks now.

So I'm calling it fixed.

Thanks,
Steve

Author Topic: Will only rev to 2,500 RPM when hot (Fixed)� (Read 4589 times)

sgoldtho

Will only rev to 2,500 RPM when hot (Fixed)�

dwf08

Will only rev to 2,500 RPM when hot�

sgoldtho

Update and solution...

christophbmw

Will only rev to 2,500 RPM when hot�

christophbmw

Will only rev to 2,500 RPM when hot�

roelpeeters

Will only rev to 2,500 RPM when hot�

sgoldtho

Fixed...