W203 Auto gearbox question

[Mad Mike]

Hello Everyone,

I have well-used C 1.8K W203, late 2003. It has an auto 'box and covered about 82K miles. My local MB dealer has had the car in no less than 5 times trying to solve a gear up-shift problem. Accelerating slowly from standstill or slowing down and accelerating again, sometimes there is a significant jerk as it changes from 1st to 2nd gear, sometimes accompanied by a brief increase in revs between gears and even the engine hunting for a second or two as it suddenly suffers an increase in load. Problem is there, hot or cold. Most of the time it is very smooth, but occasionally it is bad enough that your pasengers look at you thinking you're being really stupid!

I've driven the car with a tech. from the dealer with me, and of course the problem never occurs. The dealer has tried going through the adaption process several times. This problem and the diagnostics work started last year while the car was under warranty. Now it is out of warranty and after the latest visit to the dealer this week, still not fixed.

Has anyone experienced this gear shift problem before? My dealer has no more suggestions and are not willing to investigate it further. I don't know what to do next. Any advice greatly appreciated.

Kind regards,

Mike

 

[BlackC55]

My advice is keep on at the dealer. Because you had the complaint while in warranty it is still valid. Go and see the After Sales Manager and voice your complaint and be FIRM. You should get what you want.

 

[BenzComander]

MAF, seems to be the root cause of many problems??

 

[BlackC55]

An air mass fault will be permanant not intermitant like described.

 

[DrNick]

Only if the MAF fault is permanent!
In this case though because it appears to only be an effect while changing gear, it is more likley to be a gearbox issue, although I wouldn't completely rule out the MAF.
When mine (E300TD) started doing wierd stuff like this (hunting between gears, banging changes, not changing gear sometimes) on an intermittent basis, it was due to low fluid level in the box, due to a leak. There was a pin hole in the pipe connecting the gearbox to the intercooler due to rust. SO if the level is a bit low it can lead to intermittent faults.
I assume that the dealer has checked the fluid level. The gearbox ECU also stores fault codes that can give a clue - have these been read ever?
I also had a MAF go. This lead to excess revving and not much go, but that failed slowly and then intermittently.

 

[Mad Mike]

Thank you all for your help. Just to clarify, gearbox ECU has no fault codes stored - I was shown the printout this morning. Nothing recorded. The oil was changed on visit number 3. The increase in revs doesn't happen everytime there is the lurch between gears, but when it does, it feels like a momentary loss of drive. The subsequent take up of drive is then harsh as you can imagine.

The real problem I have now is getting the dealer to admit there is a fault. I have some sympathy with them - I drove around with one of their experts in the car for 45 minutes and the gearbox shifted smoothly everytime, leaving me a bit red-faced. Today I had hardly left their car park when it thumped into 2nd gear! The extra miles on the clock and the fuel used suggested it had been given a good test. However, the radio is always on loud when I get the car back - surely that doesn't help much in trying to hear or feel for a drive problem! All the other gears shift fine and so far I've only ever experienced the problem with gentle driving, queing traffic, roundabouts etc. Pulling away with higher engine revs and the shift is always smooth.

 

[Alex Argent]

......The real problem I have now is getting the dealer to admit there is a fault. I have some sympathy with them ........ However, the radio is always on loud when I get the car back .........

Hmmmmmm.....the mind boggles .

Is it tuned into any particular station?

Remind me which stealer it is again?

 

[Mad Mike]

Well, you'll be surprised - it is Classic FM. I hardly dare mention the dealer as I do feel they have worked hard for me, sadly without success, but think of a mill town in Lancashire with a football team called ? Rovers and you'll have the answer. I wish solving the gearbox was less of a mystery.

Mike

 

[Dieselman]

It sounds like one of the operating solenoid valves is either sticking or has a problem.
I thought there was a technical bulletin regarding the size of shim on soem of the valves being out of tollerance and causing banging shifts?

It could need a new valve chest or the existing one cleaning out.

 

[Mad Mike]

A bit more info that may be significant. The dealer never experiences the fault, they say. Not only are they more interested in listening to the radio, but whenever I get the car back the 'box is always switched to 'S'. Mostly I keep it in 'C' and I've told the dealer that. Testing the car in 'S' myself and the problem doesn't occur. In this mode, changing up/down at higher engine revs and it is fine. This tallys with driving it a little harder in 'C' where it holds the first gear longer and also is fine. I'm sure that anyone from the dealer getting in the car and thrashing it around the block, it will be fine. Maybe they just can't drive a car gently.

The problem being at low engine revs and low road speed, I think Dieselman is right and with low hydraulic pressure or a sticky valve, it shows up under these conditions. Trouble is that neither of these show up on the ECU diagnostics tests, so therefore the dealer insists there isn't a problem and they're not prepared to spend any more time on it.

How clever is the gearbox ECU? What kind of and how many sensors does it have to monitor every gear shift to give a MB dealer such a black and white fault/no fault opinion? Does every one of us drive a MB auto with occasional abrupt gear changes, enough to make an engine hunt as it tries to catch up with the sudden change in load? I don't think so. But then it seems it is my opinion vs. that of an ECU. So far, the ECU is winning!

 

[Mad Mike]

Duplicate post

 

[Rory]

This tallys with driving it a little harder in 'C' where it holds the first gear longer and also is fine.

Doesn't it start in 2nd gear in C mode? I didn't think C used first gear, unless you really boot it off the line, when mine will start in 2nd, but then drop to first with quite a 'thunk'.

 

[richard]

I have some ancient memory about this - its been a long time though -

I had a W208 CLK55 that would occasionally hit the rev limiter instead of changing from 1st to 2nd (under hard acceleration).

The dealer said there was a mechanical adjustment on the gearbox that needed to be tweaked - I sold the car before it was done, but it may be worth pushing the dealer about that.

I'd tell the dealer to change the gearbox control module, and if that doenst fix it change the gearbox under warranty as this problem was raised and repeatedly raised during the warranty ..

If you turn of the ignition with car in gear, put it in park, restart, select drive and drive off you get a nice thunk too.

Richard

ps, I always find radio, auto-lights, and aircon is off when I get my car back from Greenoaks !

 

[Mad Mike]

Thanks Guys, bouncing some ideas around here maybe we're getting to the root cause. Good point Rory, I remember reading in the manual that in 'C' it pulls away in second gear. I mentioned this to the dealer on visit 4 and visit 5 and got some blanks looks - they said it just held onto the gears a bit longer in 'S', but still used first gear to pull away. Counting the up-shifts in 'C', I'd say they were right. However, if the manual is right, the car is doing something it shouldn't. Is it possible that it is incorrectly using first gear in 'C', and then at some point now and again goes back to where it should be and abruptly bangs it into second gear? If it truly should use second gear to pull away under gentle acceleration, then there is a well-defined fault with it for a start!

 

[Mad Mike]

Okay, some more info. The only difference I can detect between 'S' and 'C' mode is in 'S' it holds the gears a bit longer, kicks down a bit earlier etc. So I assume in both cases it is still using first gear to pull away. Now for the really bad news; the same random lurch into second gear happened last night when in 'S' mode, so I'm no nearer finding the reason. Still thinking Dieselman's thoughts on this are the way to go, but again that hurdle of convincing the dealer.

 

[BlackC55]

I would try a valve body in this case. Replacing them have cured many gearbox problems for me and customers when I worked in a dealer.

 

[Mad Mike]

Thank you BlackC55. Sad for the dealer in question that they no longer have your knowlege and experience in their team. We'd not have so much to complain about and MB would have more respect if all dealers had a resource such as you.

My gearbox problem persists and my battle continues. However, I just had new rear tyres on my C180 and the gearbox problem is much less frequent. I can't imagine how. Perhaps just an unhappy coincidence? Now, I'm noticing the 'box holds onto gears much longer when cold. Gentle acceleration takes the revs up to about 3000rpm in first gear before it up-shifts with a mighty jolt into second (and this in C mode). When warmed up, things seem pretty much as normal. I once had an unmentionable make of French car with an auto box (also with electronic control) doing all the same things at about the same mileage as my Merc. A simple change of gear oil fixed it. However, dealer says they changed the oil....

 

[didgit]

this sounds alot like the problem ive had with my 200, i have now cured it with changing the ecu that controls the gearbox, the car was doing excactly as yours is doing and getting gradually worse, had the atf changed not really much diff. change the ecu myself with one that i got pre programmed from germany, took all of ten minutes, also my car needed a new cam sensor, wow what a diff this has made to the car its like new again faster smoother changes in all ways and much better throttle response to the extent were im having to be carefull in the wet as its spinning the wheels and flashing the asr light.
the ecu is very expensive but get an indipendant to put your car on test thats how i found my faults and only cost £30.

 

[Dieselman]

MadMike
have the shifts continued to get better? The reason for asking is that as the fluid has been cahnged it might be clearing out any gum stuck in the valves so allowing smoother operation.

 

[Mad Mike]

Dieselman, no, I'd say the gear changes have got worse over the whole range since the dealer changed the oil. Now when cold, they are not at all smooth, not any shift, up or down. When warm it is better, but the only issue I had was first to second, all other shifts were beautifully smooth. Now there is some hesitation in shifts at higher speeds and change down for over-taking seems to take forever. I've driven about 300 miles since the tyre change, the problem first to second is much less frequent. The hanging on to gears 1 and 2 until stupidly high revs is now more of a concern, especially when cold, as is the general quality of all changes. I know I'm a bit mad, but could the slight difference in gearing by having more tread on the tyres have such an effect? Hard to believe if it is. Of note, I'm pretty sure all that has been carried out so far is adaption, two or three times, and an oil change. What if the adaption is trying to compensate for a sticky valve?

Didgit, good point about the ECU. I've noticed it change from 1st to 2nd way too early as well in the past (but not since the new tyres) It pulls the revs down to about 500 rpm when it does it. Would a hydraulic problem cause that? In my limited knowlege, I would suspect the ECU initiated the change - clear there is a fault somewhere. I'll be at the dealer with it next week and hope the car disgraces itself in their presence without me going even more mad.

Thanks to you guys for your help.