New Member - 1999 C240 Sport Auto Kick-Down oddity

[michaelarran]

When I kick-down, the gears change as expected, and the car accelerates up to 5000rpm, and then stops accelerating, and the gears will not change until I lift my foot off the accelerator, after which all is normal, although once I tried this and the engine ran very roughly if I let it tick-over, until I stopped and restarted the car.

A couple of months ago there were a few times when the car would refuse to change gear after a cold start, but that problem has disappeared, as mysteriously as it appeared.

Are these symptoms related to the MAF that I see written about all over this forum? I am am not very knowledgeable about cars, and want to get a good idea of the problem before I take it into my local independent garage.

Thanks for any pointers you can give me.

Mike

 

[eric242340]

When I kick-down, the gears change as expected, and the car accelerates up to 5000rpm, and then stops accelerating, and the gears will not change until I lift my foot off the accelerator, after which all is normal, although once I tried this and the engine ran very roughly if I let it tick-over, until I stopped and restarted the car.

A couple of months ago there were a few times when the car would refuse to change gear after a cold start, but that problem has disappeared, as mysteriously as it appeared.

Are these symptoms related to the MAF that I see written about all over this forum? I am am not very knowledgeable about cars, and want to get a good idea of the problem before I take it into my local independent garage.

Thanks for any pointers you can give me.

Mike

Well to start, it does not sound like a transmission problem, more an engine problem and intermittant at that. But ill wait for other posts on this. This one could be the start of a saga.

 

[Glenn Smith]

Almost certainly an engine problem, during kickdown the box will not change up untill it hits the red line, this can happen in 4th quite normally as it is difficult for the engine to red line in the high gear, red line in 4th on my c230k is over 130mph, if it's doing it in the lower gears you have an engine fault preventing it from revving freely, posssibly air flow sensor, also check that nothing is preventing the accelarator pedal from moving properly.

 

[eric242340]

Post number two and the sage continues, after this short brake, no not break you fool.

 

[michaelarran]

Accelerator pedal works smoothly. No problem there.

Cheers

Mike

 

[michaelarran]

Fixed!

Well the garage has finally cracked the problem.

After trying three different Bosch MAFs (which fixed some problems but not others including chunky gear changes and a loss of power when touching the accelerator), and crawled all over the wiring to check for faults, they were baffled.

However, the mechanic remembered having problems with a cam sensor for a Vauxhall, and wondered if it could be a QA issue, so they ordered in the Mercedes part, which I am told is the same, but has been through the Mercedes QA process, and just like magic the car is now perfect.

Well done Gary at Wedglen garage in Midhurst.

Cheers

Mike