Hello People. My 1991 300E-24Valve Sportline sedan has been a dream to run for the last year, however, about 4 weeks ago, after about 6 minutes into a journey, it started rough idling. Every time i Stopped, the engine would hang, sometimes catching itself before stalling, sometimes not.

On moving away, the engine would cough and splutter, before sorting itself out after a couple of blocks. This happened 2 weeks later, again about 6 minutes into a journey (in the middle of the busiest street in Melbourne - of course!). It took longer to sort itself this time, about 4 miles, but then ran like a dream.

Last week it happened again (10 minutes into the journey and during ruch hour). I parked up, swithed off the air-con which helped cut down but not stop the stalling when I put it into drive and neutral. Took about 25 minutes to sort itself out.

I took it to my mechanic who replaced the fuel filter. There was lots of cloudy crap, so we hoped that was the problem. Yesterday (approx 80K's since the last time) It started doing it again. Once again I was forced to park up, play with the air-con and rock back and forth between 1st and reverse until it cleared up. This time, the radiator light came on about 10K's after the event and stayed on for about 10 minutes while driving. It switched itself off. I have checked coolant levels - all okay.

Has anyone had similair problems to this? My next step is to perhaps replace the plugs and the coils. My mechanic and I are resigned to replacing my car bit by bit until we get to the problem.

I was hoping some of you could share some insight to the most common reasons for this so I can at least be a little targeted in my approach

Some extra info - the car has an imobilizer and I installed an after market kenwood head about a year ago (full stripping out the seperate control & head unit wiring and completely re-wiring the speakers!)

Thanks in advance

Did you check the Crankshaft Position Sensor?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Thanks for the reply. I did not check the CPS. Honestly I did not even know it had one (oh dear!)

So far, all of my forum searching seems to centre on new plugs and coils being the most prevellant solution, followed closely by the bolt behind the rotor. This has given me something else to consider. I will start researching around this - Thanks!

Yes, go ahead and replace the spark plugs, spark plug wires, coils, rotor and distributor cap. But if it continues to be an intermittent problem, then I would consider checking the Crankshaft Position Sensor.

You might want to do a search on the forum and see what experiences other members have had with the CPS.

Good luck,

Dave

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

I had the same problem with my e320.Replace the spark plug connectors (boots)
They are about 5 bucks each.

I replaced many expensive parts before finding this simple solution to the problem you are describing.

The boots become brittle with age and cause a missfire.

That engine is overly complicated. After tedious replacement of about every part you mentioned, mine was the O2 sensor even though the light didnt turn on in the dash. Its cheap part on ebay..$25.. Betcha thats it cause it controls the fuel flow...too rich...and erratic behavior of motor.

Thanks for all the advice guys. My mechanic suggested we eliminate things rather than swap out bits (bless him!). He suggested I keep the fuel tank over 1/2 full at all times. Low and behold, I travelled over 1000 K's over Christmas and New Year and all the way through to the 17th of Jan '08. My train was late so I ran home and decided to drive in. 8 mins into the rush hour traffic - IT STARTED ALL OVER AGAIN - WTF !!!!!!!!!

We are now looking at finding a temporary replacement for the Ignition Module. I have suggested the CPS but my mechanic thinks that it would not exhibit the symptoms it does.

Any ideas? (or explanations as to why it may still be the CPS - I don't want to contradict the guy without giving valid reasons!)

Cheers

From my readings on the CPS awhile back, it seems that the CPS only has one job, identify when cylinder #1 is at top dead center. There is an article that someone else attached that I read that talked all about how the CPS works - if I still have that I'll attach it for you.

What I gathered awhile back is that if the CPS was totally bad your engine wouldn't fire, because it wouldn't know when top dead center was and therefore the CPS wouldn't tell the engine to send spark to cylinder #1 - so a completely bad CPS means no spark at all. But if one is on the fritz it could in theory cause rough idle and poor running of the engine because it knows when top dead center is only sometimes.

The other solution (that I would try first - in retrospect, as I still haven't done this yet, but did replace the CPS on my m103) is to inspect the ignition wires and coil as you have suggested. I have done a fair bit of reading on the coil and that can also exhibit similar symptoms if it is on its way out. In my case, it probably is the coil, the coil actually looks old in my car, which probably means it is old inside and not providing proper electricity to the distributor.

If you come up with something else, I'd love to know what it is, because I still have this problem occasionally in my m103, even though its only when the car is either wet or its raining out.

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87 300E
202k on the clock

My daughter had the same car with same engine. After lots of parts and frustration, the culprit was the O2 sensor, even though the light not on. Also if you haven't changed the OVP sensor, do it and the plugs.

When this happens again later, its the O2 sensor. For some reason they not last like they are supposed to on this engine.