bluebay

My 99 e320 wagon with 106K will start to misfire and goes into the soft limp home mode whenever I accelerate hard, and by hard I mean pedal to the floor. usually starts about 4000 ripms, maybe 3rd gear. Normal acceleration, pedal halfway down causes no problems at all. This was discovered by mechanic when I took the vehicle in to have the transmission fluid changed, and a recent "check engine light had come on. Codes showed misfires on every cylinder, and a speed sensor code. Changed plugs and wires, seemed to take care of misfire codes. Mechanic wants to trouble shoot more, but doesn't seem like he knows where to go. At $120 @ hour I'd like a little more definite idea of where to look. This sounds like the speed sensor conductor plate issue I've read about here. Advice and criticism accepted

matt72

i had a simaliar problem when i bought my car,codes were for maf ,changed that no good,mercedes dealer thought it was a blocked cat or section of exhaust,they then discovered that the air filter inlet,where it sucks the air in,next to the rad,was closing under accelaration,needed reattaching next to the rad,male and female parts,soft rubber pipe connects to rigid plastic housing by the radiator and stops itself sucking shut

Plutoe

It is always a no brainier when you have codes, because you follow the codes to solve the issues. The major customer service issues surround issues that you describe---an issue without a fault(CEL)

Unfortunately with the latter you really have to know the cars systems and follow the prescribed systems tests on your tester----an example the transmission speed sensors have nothing to do with misfires, but the engine management systems do.

The transmission speed sensors if they fail, the ECU will substitute programmed values enabling you to shift, but may depending on the severity will put you in limp mode, but you would know that because your dash will light up.

If you solved the misfire issues and cleared all the faults----why to spend time and money diagnosing-----diagnosing what----unless your are in the "I think that mode"---we love that mode because the car owner is now telling the mechanic where to diagnose and if it's a dead end----well that is where you the owner said to go, what's the problem with paying the bill for not solving the problem when thats where you said to go!!?? Then you get pissed off at that shop and go to the next shop and start all over!!

bluebay

Matt I'll take a look at that once my wife gets back. Be nice to think it was a simple fix like that. Plutoe thanks for the perspective. Just got back from a more detailed chat with the Mechanic, and your right he can't figure out both the misfires and limp mode. Said the limp mode would keep you in same gear, but has no control over misfires that is an ECM problem, maybe. Also said there was a transmission temp code he pulled out. I posted the question to see if I could increase my knowledge of the interplay between these systems, and to see how deep his knowledge was. This is my first time dealing with his shop, and the misfires and limp home mode were not issues I had experienced with the vehicle, but I had never tried to accelerate the car that hard. Try to find some time next week to get it back to them. Thanks again.