Q: Intermittent failure to respond to throttle

asked by on October 21, 2016

Initially, this occurred when hitting a sharp bump. Engine will drop to a smooth idle and would not respond to throttle. As I pulled off the road, I pressed the throttle repeatedly, and eventually the engine would rev up, but the car did not go: Transmission appeared to be in neutral, but shifter was still in gear. After changing many parts at high cost, the problem persisted. I finally changed the catalytic converter and now the car does this without needing to hit a bump. Can the electrohydraulic actuator do this? Something in the transmission that can disengage it and also cause the engine to not respond to throttle?
Car is at a Mercedes dealer and they are not honouring their warranty on their faulty diagnosis. Please help

My car has 175000 miles.
My car has an automatic transmission.

Hello - wow, an older classic! Your 300TE utilizes Bosch Continuous Injection System (CIS) which varies fuel pressure more dynamically than more contemporary injection systems. I would suspect fuel pressure is the problem, both for the inability of the engine to rev, and the transmissions reluctance to provide motion. The transmission uses CIS fuel pressure to regulate gear engagement, when it shifts, and to some extent, how firmly.

I would put a fuel pressure gauge on the CIS system, find a pothole, and confirm the diagnosis with some "on the road" testing. If this sounds more challenging than you feel comfortable with, I would recommend having the no acceleration condition inspected by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

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