1996 C36 Electrical Gremlins

[mbsickness]

Hi All, I have a 1996 C36 which has developed some nasty electrical issues. The first hint of a problem a few weeks ago is that the car idle is slightly lumpy (rhythmic). Since I own the car I noticed it but should another person drive it I doubt they would notice (such as a valet). A few days ago I returned from a week long vacation and the car failed to start on the first try. The odd thing is that the engine spun as if there was a lack of compression, similar to when a timing belt breaks. Eventually the car did fire up but after cranking the motor for an extended period of time (45 seconds). I drove the car that day to run a errand and all seemed normal. This morning the car fired up as it normally does but when I was three blocks away from my house the car stumbled big time. I was pulling away from a stop sign and all of the sudden I lost all power for one second. When I looked at the dashboard I noticed all LCDs were out. No clock, mileage, outside temp, etc. Upon shutting off the car and restarting the dash LCDs came back....until the next time the power cut. It seems that the only time the power cuts is when I accelerate. Finally when I was moving cars (to get to another so I could go to work) the car was missing on at least one if not two cylinders and the Check Engine light is now on (still have to read the codes tonight). Any Ideas? I'm a bit at a loss. Thanks.

[_Nick]

I don't know if the C36 has the same problems as the other C-Classes but have you replaced your wiring harness? To my knowledge, the wiring harnesses usually need replacing as they get older.

Pull the codes and see what you get. How many miles?

[mbsickness]

The car has 92K and the wiring harness was replaced at about 28K miles. I'm beginning to lean towards a bad alternator/voltage regulator pushing to many volts and thus triggering the OVP...

[mbsickness]

Well rule out the OVP as I check the voltage at idle and at higher rpms.....13.7 volts. Idles is really rough definately has a miss. Check engine light is on but no codes. Throttle is really slow to respond. I don't think this will be an easy or inexpensive fix.

[strictlyspeakin]

Light is on but no code. Odd, I'm not sure. Check the mechanical for the throttle control to make sure there's not a broken spring down there. Another off the wall idea, are there any big subs in the car stealing the voltage per se?

[anf6789]

coil packs? maf? my C280 was running funky earlier this and i replaced the o2's and maf. runs like a champ now. your problem does sound kind of electrical though :/

[mbsickness]

It's been a while and I wanted to provide an update in the event someone else finds themselves in the same situation. Turns out it was one of the coil packs that caused all the issues. I replace on coil pack and it has been fine to date. So anf6789 you were right.

[anf6789]

funny thing is. the 97 C36 I just bought is sitting in my driveway apart right now. idle is slightly off. when the car gets warm, after driving for an hour or so, it hits like an almost rev limiter at part/full throttle. Its definitely ignition related. weird thing is. none of the coil packs are original. 2 are STI/Karlyn i believe. and the other one is Meyle. if codes/datestamps are what i think they are the parts are newer than '05-'08...wires are original. and one was stuck on and broke when i tried to pull it off.

So i just ordered a new spark plug wire set and some bosch plugs to see if that fixes the issue. I still have a inkling its coils but who knows.

How did you diagnose the problem coil? I have no CEL/codes and car just passed inspection.

[mbsickness]

Mine had a constant miss and one time only it did flag a #3 misfire so I was pointed to the offending coil. After the coil swap even with the CE light on the #3 misfire code was gone...I figured I just got lucky.

[taz069]

Along the same lines of problems here. My interest is more toward the cam position sensor. I have a 96 c280. When my car does crank it runs great. So the firing of the cylinders is not of a issue. It is mainly in the getting started mode. Not for sure if mine has a crank sensor or not but will be checking soon. Keep us informed. Thanks.