S320CDI 2003 - Acceleration Gone Strange

[davidpmiller]

Hi,

I have a Mercedes S320CDI 2003, recently it has been performing strangely!!

Initially, it would not go above 60mph - my local mechanic check the computer and there was a 12v reported on the boost switch (not sure what this means).

However, he cleared the fault and the car went above 60mph but still felt like it was misfiring slightly. In addition, the gear change doesn't seem right - difficult to explain but sometimes it appears as if its not quite changing at the right time and not as smoothly. We also get some shuddering at lower speeds.

The MAF was taken out and cleaned and this seems to have made little difference - any advice on what to look at next would be greatly appreciated.

Regards
Dave

 

[Dieselman]

Check the MAF output and the EGR valve for smooth operation, after that check injector balance.

Any fresh codes?

 

[BlackC55]

Only about £40 from Euro for the MAF.

 

[davidpmiller]

Hi,

Is there any special way to check the MAF output? Also the smooth operation of the EGR valve? Otherwise is it simpler to change these?

Is there a web address for Euro - to get prices on the MAF and EGR?

Would the MAF & EGR make a difference to the gear change?

Any further help would be greatly appreciated.

Regards

 

[Dieselman]

Change the MAF anyway, it will affect power and gear changes.
The output can be measured but it probably is faulty and is cheap.

Other than cleaning the EGR don't do anything yet until after the MAF is done.

 

[BlackC55]

Search for euro car parts.

Yes a faulty MAF will effect the gear change.

Try the MAF first.

 

[BlackC55]

Great minds think alike.....

 

[Dieselman]

Great minds think alike.....

Who's that then..anyone we know...

 

[davidpmiller]

I'll order up the MAF and let you know how it goes.

Many thanks both

 

[davidpmiller]

Bought the "Air Mass Sensor" from Euro Car Parts at £130inc vat. It came as a circular unit with the mass ir filter fitted and another sensor (maybe the boost switch?) - Quite suprised at the price, but the retail was £203+VAT.

Anyway fitted the unit today and the car seems to be running a lot better. Will give it a day or so before I'm happy it is cured and I'll let you know how it goes.

Many thanks for your help.

 

[davidpmiller]

Bad news, still got problems.

the acceleration is better, but we are still getting the intermittent shuddering and occassionally the non smooth gear change.

Should I look at the EGR next?

Any further help would be apprecaited.

Regards

 

[SilverSaloon]

maybe quicker (50/50 whether it wouild be cheaper) to get a merc dealer to look at it.... they should be able to diagnose the issue very quickly

 

[Deleted member 11979]

When my E320Cdi did this it was traced to a corroded connection in the wiing loom between the gearbox and the ECU, I seem to remember something about a fan that cooled the ECU being faulty as well which had put it into a "limp" mode. I know a lot of people on here are far more technically minded than me but I thought I'd let you know.

 

[davidpmiller]

As mentioned earlier the MAF has improved acceleration, however at around 2000 & 300 revs the car seems to shudder/vibrate - it will happily crusise at 70-80mph but it just doesn't feel right. I also get some vibration underneath my feet when its playing up.

I would take it to my local dealers but they are normally useless and simply change every part they can and present me with a £1K bill!

I can get my local mechanic to get it connected to a bosch computer (not mercedes) which will cost me about £20 - is it worth doing or should I change the EGR to see if that solves the problem?

I'm due a fuel filter / air filter change - would any of these cause the problems of shuddering/vibration and jerky gear changes?

Any help would be appreciated before I need to remortgage and go to Merc!

Regards

 

[BlackC55]

You seem to have a gearbox related problem now you have posted some new details.

Your gearbox need looking at. ATF level is the first port of call then fault codes need to be read by a good tester.

Then the sump pan need removing for inspection of swarf etc.

I suspect either the box has given up or a torque converter problem but without actually seening the car and feeling the fault it is difficult to say.

 

[Dieselman]

I bet it's glycol in the gearbox causing slipping. Not sure whether the S class ever suffered but the car is the right era for a problem radiator.

It sounds like the same problem as last year only worse.

Otherwise it could be a duff injector, pump or an air leak into the fuel line.

 

[BlackC55]

Thinking alike again......

 

[Glenn Smith]

i would look at the EGR definately, or better still blank off the exhaust side so no egr can enter the inlet, too much egr will cause very poor running and similar symptoms to air meter problems, too much egr = not enough measured air and low fuel injection quantities, poor engine performance will affect the quality of auto gear changes. Merc dealer should be able to do a glycol test on a sample of ATF if you want piece of mind here.

 

[davidpmiller]

Just had the car put on a new bosch computer and it says there are no faults!!!

Will be getting the gearbox ATF tested tomorrow.
Would the computer say if the EGR was faulty / injector was faulty?
Should I change the fuel/air filter ?

Regards

 

[Dieselman]

Injector or EGR faults should have been picked up and registered codes.