C200K Intermittent Loss of Power

[JonathanC]

Hi All

After selling my E320 a couple of years ago my wife decided last year to buy a '02 C200K auto estate. Very nice car but seems to be very problematic.

When we bought it it was said to have had a new MAF. On driving home I noticed that it hesitated when pulling away. After reading a few posts on here I decided to reset the throttle position sensor - this resulted in the CEL coming on. Took it to a dealer to ge the codes read and they idnetified MAF issues but reset the codes and said see how it goes. Anyway after about 120 miles it came on again. My wife thought the car was OK so we decided to leave it and see what happened. During the cold snap we had before Christmas I drove it and it felt like it had become a 1.6! No go at all but ran smoothly and idled OK. Took it to a local indie who diagnosed a MAF failure and duly replaced it (fortunately paid for under warranty). This seems to solve the problems and the car was going like a rocket so thought it had been fixed. Driving it a few weeks later I noticed that it was reluctant to change down gears and would labour at 3k unless the kickdown was acivated. Shortly afterwards the power dissappeared again (during a couple of cold days). It then seemed to recify itself but shortly after the CEL came on again - went to garage who read the codes and found an "undocumented" code - reset it and said "see how it goes" Although it is OK it feels about 80-90% of its best and the gearbox is still occasionaly reluctant to change down under load.

So after that, I wondered if it is a problem with the throttle position sensor - anyone have experience of this or have any suggestions what else it could be. As I say car idles reasonably well (slight hunting but not enough to worry about) and pulls smoothly.

Thanks

Jonathan

 

[television]

Jonathan do lift the air cleaner off and see if the are any oily deposits in the MAF

 

[JonathanC]

Hi Malcolm

Checked the MAF, seems ok. I am convinced this is an issue either with the throttle valve or the sensor. When it does play up, the first 1/8 of accelerator seem to be normal but then giving it more gas has little effect. I also remeber exoereincing an issue with the cruise accelerating over the set speed but this may have been a wheel sensor.
I guess I need to inspect the throttle valve to see if it is clean and moving freely.

Cheers

 

[jberks]

when my MAF went, it took the O2 sensor with it (runing rich I guess). Similar symptons, hesitation to accelerate, safe mode etc..

 

[tjoneill@btconnect.com]

hi,after fitting a maf sensor the throttle body must be cleaned out, the fault codes cleared and the adaptations reset. [boot strapping] or fault will keep reappearing

 

[JonathanC]

hi,after fitting a maf sensor the throttle body must be cleaned out, the fault codes cleared and the adaptations reset. [boot strapping] or fault will keep reappearing

Good points, I think the garage cleared the codes and reset the adaption values. Not sure why the throttle body would need cleaning out after a MAF change though - however I think this is the problem.

Good point about the O2 sensor but this hasn't thrown any codes. Currently the CEL is still off although the gearbox is still reluctant to change down and I don;t feel it has full power, maybe 80-90%. Hopefully this weekend I will get a chance to clean the throttle body out, anyone suggest what to use, or just normal Gunk stuff?

Thanks