Sudden Stoppage Syndrome - Can you guess the problem? - thread will include answer

[brewtoo]

Seems like we forever see people posting problems and asking questions but we hardly ever hear if a problem gets solved and if so, how?

So, here is my problem - And Solution - all in one thread.

Last week I was turning left through an intersection in my 1991 124 300E M103 (so you will know the model and year of car - pretty cool idea?). Anyway, the car was making an awful knocking noise and was barely running. I pulled into a parking lot just time for it to quit. It would not even think about restarting. Had to leave it.

Next day, finally got it to run, sort of. Missing badly, pinging, weird-smelling exhaust. The wrecker did not show up to take it to an indy about 4 miles up the road. I decided to give it a try. Made it to within 1/2 mile of shop. At this point the engine would idle but would miss and quit if you touched the gas. Had to call another wrecker service. $65 for the last half mile.

The mechanic listened to the car. It was putting up quite a fuss. Running, but missing and pinging, except when it would mysteriously smooth out. I put it in drive, foot on brake and brought RPMs up to about 1500. It was missing good now. Cylinders 2 and 4 were dead. Mechanic pulled plugs. They did look bad - gap had worn to about .060, oil-fouled. I was embarrassed. He fussed about them being NGK plugs. He regapped them to .040. Car ran smoothly now but I did not trust it. When was the last time spark plugs brought a car to its knees all of a sudden like that? Like flipping a switch. So I drove it around a bit. It was fine for about a mile. Then it went nuts again. Barely got it back to shop. I gapped all the plugs to .040. Same thing happened again. I bought six new Champion copper plugs, gapped them to .040 and installed them myself. It started right up. Perfect. I was amazed! I drove it about 12 miles home, no problem.

Next morning, sitting at a red light and it missed real bad. Uh oh! Started doing the same thing again but not as bad. Maybe one of the new plugs was bad? I re-gapped the plugs to .032. No help - still missing. I put some old Bosch plugs in (still good). The dang car would barely even start at all! So I had an old set of Champions just like my new ones. Put them in. Car started right up, nice and smooth. I was really puzzled. My car only will run on Champion plugs? Strange.

But no, the miss soon came back. I learned that if I braked with my left foot and kept the throttle open just a tad, it would run smoothly and never stumble. I drove it over 100 miles this way. But after a while this method began to fail, it started missing and stumbling again, went dead sometimes but would always restart, and I really lost confidence in the car. Sometimes it would just quit - first shaking and rattling - while running in the driveway - with AC on, in drive.

It would tease me by running perfectly for a few miles and then stumbling badly, just when I thought it was ok. And....on the interstate it would run perfectly always, only giving trouble at idle, or sometimes at the beginning of acceleration it would stumble.

One of the odd things about this was the nasty noise it would make when it stumbled, like it had suddenly turned into a rattling diesel. It sounded like an old Chevy 350 that would run on after you turned off the key.

I've accumulated spares of parts over the years and I did do some swapping of various things. Tinkered with this and that, adjusted lambda, checked codes (none, BTW), put in some Seafoam, stared at the engine a lot. Read lots of posts on this site.

Eventually, today I stumbled on the problem. I was all set admit defeat and take it to the shop tomorrow.

Before I post the answer, can anyone say what the problem was?

[Richard Wooldridge]

I would guess something to do with EGR...

[LUVMBDiesels]

Coil?

Plug wires?

CPS?

How about a loose ground strap?

[pawoSD]

Worn distributor cap or rotor? Loose wire from the coil?

Something unplugged?

[amosfella]

crap in your gas and a ripped filter??

[appatula]

OVP Relay?

[suginami]

I hate puzzles and I hate waiting.

[ejsharp]

My guess is that it went into some sort of fail-safe mode.

[satyr]

Only because I have weird luck and have had the following problems in my "gassers": (so these may or may not be helpful)

1.- Leaking heater hose getting ignition components wet.

2.- Spark plug wire (s) burned on exhaust and shorting.

3.- Distributor clamp/bolt loose.

4.- Distributor cap loose.

[brewtoo]

OK, sounds like everyone has done their homework and has guessed the same things I did.

The problem turned out to be one little part........

The Distributor Rotor.

I was not convinced it was the ignition at all, and even less convinced that the problem was in the secondary side.

I would have never thought a rotor could bring a car suddenly to its knees. Or make it (sort of) run only on Champion spark plugs. Or run fine when you kept your foot on the gas all the time and braked with your left foot. And why did it run fine on the highway but not in stop and go traffic? Seems like the load would be higher on the ignition system at high speed/high load.

I had to go to Autozone to get a replacement over the weekend (not Bosch). I had checked the old rotor. It looked good and the resistance was just over 1Kohms (within spec). I had little hope that the rotor was faulty but, in desperation really, I replaced it. The car ran perfectly! I put the old one back in and once again, it was going nuts, coughing, missing and spitting. So I installed the new one again and - smooth as silk.

So, there is a lesson here for us all. Check the simple things first and don't let anything surprise you.

I love a good challenge and it felt good to win! And this was not nearly as much work as that evaporator!

[pawoSD]

I win. I was first to name the right part at issue. Once I replaced the wires/distrubutor cap/rotor/plugs, my 300E ran waaaay better. (and still does run excellent)

[cliffmac]

that's great, but what I would do at my first earliest convience is scrap all that junk champion and god knows what else component crap and replace all of it with the original equipment Bosch stuff...believe me, if you intend to keep the car for any period of time you will understand why....i have learned the hard way and the soft way...i prefer soft... if you just want to get it running OK and dump it then your way is my way. best of luck

[ps2cho]

Visually, how did it look? I have been told Rotor + Cap should be visually obvious if they are suspect.

[cliffmac]

otherwise...what can I say...sounds like baiting to me....

[cliffmac]

seems as if BrewToo needs some attentions...that's OK Brew 2...that's good what you have done....