joerd7

Recently got my 1991 300e back from service. Said stalling when warm was due to clogged cat. converter....not so. It seemed to run decent, but was getting bluish smoke from exhaust, mechanic said it sat too long and needed to run. Once it warmed up and I tried to move it, it stalled and would not start again. Started the next morning with no problem, but it was cold. Is this the OVP relay? How can I test it?

hineywineries

Need more input. First of all who said converter was clogged, and who said it was not? How was it tested? Also do not understand what blue smoke has to do with anything. Do not suspect OVP relay. How long did car sit without being driven? Please provide a chronological list of details so I can be of more assistance.

joerd7

Thanks for replying...will try to give as much info as possible. August 2010 while driving, car would studder then stall and would be unable to re-start. This happened approx. 5 times. Checked plugs, rotor, wires, tested coil these seemed to be alright. Read on MBWorld of all problems it could be so I sent it to a recomended local mechanic to diagnose and repair. Mechanic was extremely busy and said it would take awhile, had another vehicle to drive so it wasn't an issue. Car sat until December 2010 when I contacted the mechanic and he said the cat. converter was clogged causing the stalling. A few days later he called and said the car was ready. Picked up car and drove it home...seemed to run okay but idle was about 500 barely holding it's own and the exhaust was smokey with a noticable odor. The mechanic said it was probably because it sat too long and gas had broken down a bit. As of now the car with start just fine cold, idle is low barely running by itself and once it comes to temp. and try to move it stalls and will not re-start until it is cold once again. Replaced OVP relay and new air filter...both had no effect.

Lester Lugnut

I went thru something very similar a few years ago with my '91 300-SEL - M103 motor.

In warm to hot weather - it would konk out after about 15 miles of driving. Let it sit for an hr. or so and it would restart. Car was still warm - so it would die again after 2-3 miles of driving. Let it cool off over night and I'd go about 15 miles B4 it died.

Problem -> bad fuel pump - original Peirburg pump had given up the ghost.

Not saying this is your problem - just sharing information.

hineywineries

Not buying the bad cat and broken down gas story. I think you need to find another mechanic. Did he explain to you the procedure used to determine the cat was defective? You can perform exotic cast on the cat within infrared thermometer, however, there is a much simpler test. Most young modern-day mechanics warship the diagnostic scanner as a God.They lose sight of the fact that one the most important diagnostic tools in the shop is a vacuum gauge. To do a quick check for a clogged cat hook a vacuum gauge to manifold vacuum.Read manifold vacuum at idle, and then accelerate engine to about 1500 to 2000 RPM.When you accelerate to this speed vacuum should drop sharply and then rise to a reading above your idle reading. If high-speed reading is well below idle, you either have a restricted cat or retarded valve timing. It is hard to say what your real problem is. It could be a failing fuel pump as the other person suggested, but it could be the distributor, ignition module, coil,etc. All of these are common issues to the W124 chassis with gas engine.

phoenix244

hey Joerd7, i'm having similar issues. What was the problem in the end? Thanks for any help, i'm stressing!