QuestionDear sir,
I hope you can help me with this problem. I am working on a '91 benz 300E with the I-6 3.0 gas engine. It has been running great, but then all very suddenly it just died, without warning as I lifted off the accelerator to turn a corner. It started right up again and ran great for a few more blocks and then it died again. It would start
and idle ok but if I pushed the accelerator too suddenly it would cough and run extremly rough, (flooding?)
but if I could coax it past about 1500 rpm it would rev until I let off. At first I was thinking fuel filter but I'm not so sure now as it acts more like too much fuel. The next day it would start but I could not get it to build up enough rpm in gear to move very far without stalling. In park I could get it to rev up once it got past a certain rpm (1200-1800) and it would rev up to redline no problem, but as soon as I let off, it would die. It would Idle fine, just when I put a load against it (in D) it would studder and shake. It would die almost instantly when put in reverse. It kept getting worse to the point that it would not start at all (fauled) and I had to tow it to a shop.(independant benz service specialst) I had the shop look at it
and they checked the fuel pressure (82 psi) and found the cap and rotor to be in need of replacement and the plugs (platinum) fauled. I don't know where they checked the pressure. They replaced the plugs with stock Boch and it would at least start again but run horrorable, I could not get it to rev up at all. They said to replace the cap and rotor so I did, with all Boch parts. It did not make any difference. As a side note, in the week prior to this I had noticed a very strong fuel smell and I found it to be a leaking E.H.A. valve. I replaced it and it did not change how the car ran at all. It currently will run
very rough and die as soon as the accelerator is touched. I have checked for vacuume leaks and can't find any that I am aware of. The check engine light is now on, it wasn't before. I had my brother start it while I stuck a long sqrew driver to the Idle control valve and I could hear the motor whirr and then click when he shut off the ing. The plugs are getting plenty of spark as I can see them but I haven't tested them, just very white spark when pulled. They are not generally dripping wet but have very black, kinda soot-like deposits and number 4 and 6 seem like they are a bit wetter than the others. They maybe have just a little oil on them but not very wet. The fuel pumps are running as you can hear them when you turn the ing. on and then they stop after 3-5 sec. No one seems to be able to help without a lot of diognostics. Is there somethin common on these that I am over looking? All the lights and electrical work fine so I don't think it's the OVP. relay as has been suggested elsewhere.
I just don't have any other ideas.... Please help if you are able as nobody can seem to with out breaking the bank. I sure would appreciate any help you could give me. I love this car and I'm pretty sure that it is something small, I hope.
P.S. The valves appear to be opperating as they should so I don't think it's the timing chain, although the car has 155K on the clock and I don't know if it has ever been changed.
AnswerBest guess:
This requires heavy diagnostics, you have found two issues, and described at least four more current issues.
I suspect three more issues.
There are no options that will be cheap or easy, this is a Luxury car.
I suspect:
#1. Bad injector wire harness + bad engine harness.
#2. Bad valve guides.
#3. Fouled spark plugs.
#4. Low compression.
#5. Bad Altitude Sensor.
#6. Leaking Cold Start Valve
#7. Leaking Fuel Injectors
#8. Possible bad Fuel Pressure Regulator
#9. Damaged Oxygen Sensor
#10. Bad Water Temp computer Sensor
MB Wiring Harness Failure
http://www.mercedesshop.com/shopforum/showthread.php?p=927185#post927185
