Bad Camshaft Position Sensor?
 

What are the symptoms of a bad camshaft positioin sensor? I've been a chasing a rough idle on a 92 400E, 140k, for many months now (although I've not been driving it much). The car idles rough, shakes at idle, but only at idle, like bad motor mounts, but the motor mounts have been replaced. But when you drive the car it's smooth, can't tell anything is wrong with it. The reason I suspect the camshaft position sensor is 1) virtually everything else has been replaced and/or tested, and 2) disconnecting it has no impact - good or bad - on how the car runs. It's maybe a hundred dollar part so I guess I could just buy a new one and see what happens (as I did with all the other things that didn't fix it).

Does anyone know what the symptoms are for a bad camshaft position sensor or how it can be further tested? It's not putting off any fault codes.

The cam sensor is used to position sequential fuel injection. I am pretty sure that is all that happens if you disconnect it is the injectors are group fired instead of sequentially fired. This is the way it works for many engines. I'm not sure about all. Try disconnecting it while running. That is if you can clear the code it will cause. I doubt the car will do much more than a small one time shudder.

I tried disconnecting it while the car was idling - nothing - no difference at all. Back and forth - no impact at all. Pulling it does create the camshaft signal fault codes - which I do erase. But as long as it's plugged in I don't get any codes. It seems like if it was working there'd be something different about the way the car ran. I'm still suspicious that there's something wrong with it.

As I stated there is no difference, only the slight posibility of a momentary pulse difference.

The computer changes strategy from firing injectors once an ignition firing in firing order to firing twice an ignition firing at smaller pulsewidth all at once.

You could probably see the event if you looked at the O2 sensors. But only briefly as fuel trim is, maintained and the system stays in closed loop.

The need for sequential firing came with OBDII rules that required shutting down misfiring cylinders fuel input. That couldn't be done without shutting off the motor if they all fire at once which is the way it was done up till about 94-5 in most cars. MB changed to LH in 92 for this specific reason. No way to do this with KE.

So you're saying you don't think the CPS is the problem, or just that disconnecting is not a good test? I'm running out of possibilities - it's got good compression, new engine actuator, new wiring harness, new plugs, new plug wires, new caps and rotors, new fuel pressure regulator, new motor mounts, new O2 sensor, new EGR valve, cleaned injectors - it's basically refurbished and yet it still idles rough, quite rough really. And there's no fault codes. Where to go next?

The OP states EXACTLY what I am experiencing!! He has replaced similar parts to me also. I wonder if he ever fixed it...

Either way, I think I am going to replace my CPS and hope for the best. It is expensive at $120...but I gotta get this wrapped up as it has been too long now.

My sensor currently measures within specs, but I have heard that it does not necessarily mean that it is functioning properly.

At least its warm for you when replacing it....I spent 2.5 hours outside when it was EIGHT degrees trying to replace it on the 300E....engine had not been run in 2 days, so it was FROZEN cold.....your hands/arm cool off very quickly when squeezed against an 8F intake manifold....I'm lucky I still have all my limbs....I couldn't feel most of them when I was done! :eek:

The 2005 posts were talking about the camshaft position sensor found on an E420, not the crankshaft position sensor. The M103 engine found in the 300E does not have a camshaft position sensor. Mark

Hey! I was wondering it it's possible for the camshaft position sensor to go bad and not giving out any code, because i am getting p0300 and i think it's the camshaft position sensor the car run rough high idle.

Well to correct, it does, but it only provides information for the cluster. It has no influence on the Jetronic system.

You can test resistance on the wire itself when unplugged from the EZL. IIRC the acceptable range is 800-1200omhs.

No, the M103 engine has a crankshaft position sensor, not a camshaft position sensor. You are correct that the crankshaft position sensor provides a signal to the EZL and your resistance range is correct. Mark

What is the sensor that is located at the front of the engine that provides data for the tachometer then?

The front sensor provides the engine speed to the tach and the TD circuit signal to the X11 diagnostic connector. It's nothing to do with the EZL. The specs for the crank position sensor are actually 680-1200 ohms.

The 103 engine in my car has a Crank position sensor near the pulley . no cam sensor .
mak

Camshaft position sensors are installed on engines with variable valve timing---M103 engines do not have this feature. Mark