Limp home question (after search!) - PeachParts Mercedes-Benz Forum

rbn3 · #1 03-03-2004, 05:38 PM

My 92 500e had 71K and runs perfect except...when in goes into limp mode. I have read the voluminous posts on this subject and know I am in way over my head.

But this one happens only on warm re-start. If I let it sit for a few hours it will start and run fine. It has never gone limp after a good start - only on warm re-start. Sometimes just shutting it down and restarting "fixes" it, but often it doesn't. Obviously I cannot trust the thing if I go somewhere and can't get home faster than 20 mph!

Does this symptom pattern suggest the cause, or do I have to start on the arduous jouney described in other posts? I have a great indy who has not taken a crack at it yet (he works on all three of my '92's and so far has been a diagnostic genious), but I don't think he has the diagnostic equipment of a dealer, so I'd like to offer any clues you guys might have on where to start.

TomE500 · #2 03-03-2004, 11:11 PM

That is exactly what mine was doing intermittently at first and then after 6 months or so, it was on all the time.

The reason for the intermittent is that some times , the potentiometer that ccontrols the dohicky will come unstuck and sometimes it won't. The pot is a lousy design for these Gorillas and one of the reasons why a radical fuel management sys change in the 96+ MB 119s.

Only authorized MB parts rebuilders have equipment neccy to replace the pot and rebuild the unit which is mostly just replacing the pot. That said, call you indy and ask him if he has any other 119 engine MBs in for repairs. If he does, ask him to swap out the Throttle body (pop the aircleaner and only 2 bolts hold the TA to the engine, remove the wires to the EZL[inspect harness for cracking] scrape off the gasket, R & R with the unit from the other Benz with a new gasket ($3.80) fire her up clear the codes and winde her up baby. If that solves the problem, you need the unit part number above and they aint cheap. You can try the pigtail wire under the drivers side carpet which rarely causes the problem but it rarely solves the problem. If you still have the problem with the TA from the other vehicle, the EZL could be on it's way out and that sucker is ridiculously priced in the 2-3200 range new - ouch!

Tom

Jim's500E · #3 03-04-2004, 03:38 PM

Me too, been there...however, the part # for a 1992 is different than a 1994 for the TBA.

The 1992 TBA was like $700 while the 1994 TBA is closer to a $1000. Who knows why? Mine was lucky enough to last me 135K miles...but as evident by your lower mileage car (and others) that mileage and maint. mean nothing when it comes to this/these gremlins. PITA.

If your indy can do what Tom suggests; which is a great idea...you can rule out or find out that the TBA is the cause. Sorta wish I had that option while I was tracking down the same problem. If it isn't the TBA...look at some of the lessor costing items like a bad alt/volt reg, stop lamp switch, crank position sensor, nuetral postion sensor, wiring harness, etc.

Post what you find out !!

rbn3 · #4 03-04-2004, 03:41 PM

Thanks guys... very helpful suggestions.

The 500e is still tucked away for the winter, but I'll take it in soon along with the suggestions. I'll keep you posted.

vincec · #5 03-04-2004, 06:27 PM

Rbn3,

Sorry to hear of your troubles. I had to replace my electonic control module recently because of the limp mode problem. You mentioned your car running smoothly if its not a warm start and that restarting 'fixes' your limp mode. From what you say, it does not seem to be your EZL, which based on the current price to replace, is hopefully good news for you. When my EZL went bad, neither restarting or non warm start ups would cure the limp mode. Just my 2 cents....

tom woolner · #6 03-07-2004, 02:08 PM

Several months ago, my 92 500E going into limp mode, right after a cold start. It would sometimes take two to four restarts to get it back to normal. It would not happen with a warm start. The intervals were becoming closer and closer. The computer thre out the code for the dreaded throttle actuator.
However, it just stopped doing it! Hasn't done it for months! Now, I'm pretty sure it is a temporary reprieve, but I'm not going to deal with it until it comes back as a problem.
Any suggestions, guesses, why it just stopped?

Tom
92 500E
130,000 miles

PS the starter began intermittant not-starting on the first try, intervals becoming closer togetheer, and it stopped doing it too!

placo1 · #7 03-07-2004, 05:24 PM

Tom,

Have you checked your wiring harness? A couple of wires touching could definitely cause intermittent problems and just the right amount of vibration/moisture/heat can make the problems reappear.

rbn3 · #8 03-30-2004, 10:47 AM

Took the car out this morning - it ran like the day it was born. Stopped the car after a short drive and tried to re-start - no power - hardly enough to even go, then enough to go. Let it sit for an hour, it ran like a top - drove it to the shop and turned it off. It did the same thing with the mechanic watching - ran rough and no power.

His first question - did (does) the check engine light come on? It doesn't and never has when it does this stuff - what does that mean? I will call the shop this afternoon and post their "preliminary" diagnosis.

placo1 · #9 03-30-2004, 11:04 AM

I believe the check engine light only comes on when there is a problem with the emissions system. An electrical problem elsewhere won't turn it on. However codes should be stored in the computer which can at least point you in the right direction.

rbn3 · #10 04-06-2004, 01:58 PM

...runs great. Mechanic spent alot of time chasing the intermittant warm re-start problem. Computer threw a code indicating communication problem between fuel system and computer. Mechanic's best estimate is that it's the airflow meter. Says it has a "hot wire" to assist warm re-start - so that would fit. He didn't replace it ($$$$) since after he "ohmed" the connections and reconnected them he could not reproduce the problem in spite of trying for several days. Of course, will it run right for a day, week, month of ??? is the question. Wiring harness, TA, and airflow meter may be in my future - big ticket items!

Sure is great to drive when its right!!!