rsmcmahon

92 400SE has an intermittent rough idle and stalling problems.

It usually occurs shortly after reaching operating temperature. It may suddenly die at idle, be hard to restart, and then miss under load at lower RPM. Or it will start missing under load, refuse to idle, etc. These episodes may go on for half an hour and persist if the car is shut off and restarted. Then it will clear up and run well for some time.

I dont' get a check engine light. I've checked fuses in the Control Module. (NO OVP Module in 92 400se)

I've done a search on possible solutions.

I've called the dealer to see if they will read the engine scan codes but they are booked up due to the holiday weekend.

I've changed the distributor caps, rotors, wiring harness, sparkplugs. I'll be changing the following parts today.

Fuel Pump Relay
Fuel pump
Fuel Filter
Fuel Pressure Regulator
Ignition Coil
Air Temp Sensor
Oxygen Sensor

I called the local Autozone and they dont read engine scan codes on Mercedes. Any non MB that can read scan codes?

Thanks in advance for any suggestions.

Russell

Dual 5Ls

I think within that list of parts you're swapping out, you should find a solution. Also, do them one at a time and drive the car afterwards so you know exactly what fixed it. I'd REALLY like to know as it sounds similar to my problem. I'm thinking the fuel distributor, or whatever the hell that is, might be the problem, but the fuel filter on my car is pretty old... Let us know!

ghost

If i had to guess..i would guess one of two things.....i think when you do the oxygen sensor and ignition coil..it will be solved...

Unless it has to do with the fuel assembly...


post back to tell us how it turned out...


ghost

rsmcmahon

My problem is FIXED!
Well, I ended up approaching the stalling problem with the “shotgun” approach. I changed the coil, fuel pressure regulator, fuel pressure sensor, O2 sensor and fuel filter. I ordered the parts online and the fuel pump was the wrong part so I didn’t replace this part. I’m unsure which one of the replacement parts actually fixed the stalling issue since I changed all the parts before driving the car. Anyway… I’m very pleased the stalling has stopped.

Replacing all the parts at once isn't the best way to trouble shot exactly which component fixed the problem, but since the problem was sporadic and I didn't want to spend the extra hours with a hot engine, I just did them all.



Thanks,
Russell

Dual 5Ls

Great news! Where did you order your parts from? I'm thinking in my case its the coil. Maybe thats what it was with yours. Heres an easy way to tell, put the old coil back in now and then you'll know! I'd be very interested in the results if you did that.

Klasse Ac'

Knowing modern EFI cars in general and there emissions systems the rough idle stalling and all around poor lowspeed travel could be mostly the oxygen sensors. In many cases, the computer doesn't know the oxygen sensor is bad, you dont get a light. It may only give you a light when the sensor is is disconnected. This is with most American and Japanese technology, i dont think German would be much different, though i could be wrong.

Well all that matters is that you got it cleared up. If you dontmind my asking, what was the price for the fix?

Jer

In the future, you should get a pulse reader and a lambda tester so you can figure out the problems exactly (or at least get close to it). Actually, do the earlier W140s even have pulse readout? I'd imagine so, as the W124s around this time still had them.

rsmcmahon

BJ,

After I replaced the coil (and other parts) and after the car over came the stalling problems, I trashed to old parts. I agree, changing a single part at a time would have been the correct method for identifiying the defective component. But since I was rushed to leave town, and since I did not want to wait for the engine to cool between replacing parts and testing, I resorted to changing all the parts at once.

I figured most of the parts would be future problems anyway - so why not just replace them now.

Russell

rsmcmahon

Klasse,

You had asked what the repair cost were. I did the work myself so..... below are the parts cost.

Fuel Pressure Regulator x 1 @ 36.59
Fuel Pump Relay x 1 @ 22.61
Oxygen Sensor x 1 @ 81.94
Air Temp. Sensor x 1 @ 10.26 (wasnt' related to stalling)
Fuel Filter x 1 @ 23.37
Ignition Coil x 1 @ 102.82

I wanted to change the fuel pump, but I was sent the wrong part , so i did not change this part. My 92 400SSE has dual fuel pumps not the single fuel pump that was listed on their website.

I also added Redline fuel cleaner to my gas.

Russell

MB AMG

Glad you got the problem fixed. My '92 600SEL has sort of a similar problem. When i've driven the car for a while and the temp guage is at the line between 80 and 120c and I attempt to start it after it's been sitting for 5-10min, it hesitates slightly. it sometimes has a rough idle in cold but that's it.