Odd problem, strange symptoms

[Parrot of Doom]

Well its a bit weird, so I'll explain. The car is a 1997 W210 E300TD saloon with 165k

Basically, twice now (since I bought the car in November), after full acceleration and then backing off immediately, I've felt the car lurching - as if its braking unevenly. This has been completely random, every other time the car behaves perfectly.

The first time was onto a motorway, the engine was probably up to temperature (was a while ago), I flew up the slip road, and straight away had to slow for 40mph roadworks. While braking, the car seemed to be momentarily applying the brakes and then releasing them.

The second time was today, engine running for about 5 minutes, I accelerated hard up to about 45mph and backed off to slow down (no brakes), the car did it again.


Now on both occasions I don't particularly remember what the tacho was doing, but I don't remember the engine changing pitch - so I don't think its the gearbox making funny changes.

So, I suspect that either the brake assist is doing odd things, or that I'm getting momentary lapses in the fuel supply to the engine - or perhaps something else that you guys might suggest?

Is there a primary fuel filter close to the tank that I might change? Perhaps I should change the diesel I use? I've already done the one in the engine bay, and the engine oil. Next is the gearbox fluid, but the gearbox makes good changes - however when the car is cold in the morning the gearbox gets a bit confused, and won't change from 3 to 4 without see-sawing back and forth between the two gears. Once warm, its fine. I'm hoping that a fluid change will sort this behaviour out.

 

[Dieselman]

I doubt the problem is fuel related because whenever the engine is on over-run the fuel is shut off.
Things to check would be the accellerator pot is going fully home, the brake light switch isn't making just when you lift off the accellerator, the timing chain isn't slack, the flex disks for the propshaft are ok.

The gearbox fault sounds possibly like the MAF sensor playing up.

There are no additional fuel filters under the car, just the main and pre filter in the filter head.

 

[Parrot of Doom]

Well, I'm hoping that the ATF change will correct these problems, what I'm a bit worried about is finding odd colours in the pan, or large chunks of metal Still, a re-conned box wouldn't worry me, I don't consider large bills to be a big problem - especially when I see the depreciation my neighbours suffer on their new cars

I did experience another odd thing today, turning 90 right at a set of lights at about 20mph, when I accelerated the revs just rose without any drive, until something engaged - although it could easily have been loss of traction as the surface was wet and the camber was odd.

 

[Stratman]

I did experience another odd thing today, turning 90 right at a set of lights at about 20mph, when I accelerated the revs just rose without any drive, until something engaged - although it could easily have been loss of traction as the surface was wet and the camber was odd.

When I were a lad I had a Daimler V8 (the Mk2 Jag shape). It suffered the same problem, revs but no drive, until there was a bang and the transmission hooked up and it took off like a scalded cat. It was simply low fluid level in the auto box (Borg Warner 35 for spotters).

 

[Parrot of Doom]

Blimey. Right, well I've got a drive to Birmingham tomorrow (from Manchester), so I will get that tested immediately.

If that is the case, oes the computer not have any sensors to warn a driver of low fluid in the gearbox? I would have thought that was rather important (like engine oil)?

 

[Stratman]

If that is the case, oes the computer not have any sensors to warn a driver of low fluid in the gearbox? I would have thought that was rather important (like engine oil)?

"Oh no Sir. The Mercedes Benz is a superior motor car and the transmission is sealed for life."

Yeah right. Take it to an independant garage that specialises in Mercs and suchlike and they will check it for you. Make sure that they use ONLY the MB fluid. It's pricey but will not knack your transmission.

 

[Parrot of Doom]

I bought the bits the other week, 7 litres of Merc ATF, a gasket, and filter. Planning on doing the job soon, its just bloody cold at the moment.

As for level, I was just going to refill it with however much came out, but on second thoughts I might buy a dipstick to be sure.

 

[230K]

I bought the bits the other week, 7 litres of Merc ATF, a gasket, and filter. Planning on doing the job soon, its just bloody cold at the moment.

As for level, I was just going to refill it with however much came out, but on second thoughts I might buy a dipstick to be sure.

I would advise buying the dipstick, it took 7.4Litres to refill mine and that was with the torque converter drained. Be carefull when dropping the sump it holds about a pint of fluid even with the drain plug out and when you take out the old filter a small qty of oil will drip out. Be squeaky clean while doing the job and it is better to drain when the oil is warm.
Also get youself a little funnel that goes into the dipstick tube for filling if you dont you will make a mess.
Keep us informed how the car goes once changed, mine now has a very slight whine/whistle in 2nd and third until it heats up that quiet as a mouse.

230K

 

[BenzComander]

I have experienced a similar strange feeling from the car recently as well. While driving along at about 50 mph, there is a feeling of what I can only describe as a gentle bumping back and forward through the car, accompanied with a very slight rise and drop in revs, but not in the speed of the car?

Car is a W210 320 petrol auto with 148K on the clock.

Any thoughts please?

 

[Parrot of Doom]

I have experienced a similar strange feeling from the car recently as well. While driving along at about 50 mph, there is a feeling of what I can only describe as a gentle bumping back and forward through the car, accompanied with a very slight rise and drop in revs, but not in the speed of the car?

Car is a W210 320 petrol auto with 148K on the clock.

Any thoughts please?

That sounds like a dodgy MAFS to me. Mine does the same when cold, feels like a gear change almost.

 

[BenzComander]

That sounds like a dodgy MAFS to me. Mine does the same when cold, feels like a gear change almost.

Thats exactly what it feels like, almost as if the car is doing a gear change but not quite.

MAF Sensor maybe then

 

[Dave K]

Either that or lazy lambdas sensor(s). They can give a kind of surging effect once the engine is warmed up and you are driving under light to medium throttle.

 

[Parrot of Doom]

Thats exactly what it feels like, almost as if the car is doing a gear change but not quite.

MAF Sensor maybe then

Try driving the car with the MAFS unplugged, see if the problem persists.

 

[jgevers]

I have experienced a similar strange feeling from the car recently as well. While driving along at about 50 mph, there is a feeling of what I can only describe as a gentle bumping back and forward through the car, accompanied with a very slight rise and drop in revs, but not in the speed of the car?

Car is a W210 320 petrol auto with 148K on the clock.

Any thoughts please?

I would check the lambda sensor switching frequency. It sounds like a 'lazy' lambda sensor reacting too slow. I would expect the switching frequency to be about 1 Hz at idle.

A slow switching lambda sensor will not show as a fault code on a W210.

 

[grober]

Rear Subframe Bushes?

Well its a bit weird, so I'll explain. The car is a 1997 W210 E300TD saloon with 165k

Basically, twice now (since I bought the car in November), after full acceleration and then backing off immediately, I've felt the car lurching - as if its braking unevenly. This has been completely random, every other time the car behaves perfectly.

The first time was onto a motorway, the engine was probably up to temperature (was a while ago), I flew up the slip road, and straight away had to slow for 40mph roadworks. While braking, the car seemed to be momentarily applying the brakes and then releasing them.

The second time was today, engine running for about 5 minutes, I accelerated hard up to about 45mph and backed off to slow down (no brakes), the car did it again.


Now on both occasions I don't particularly remember what the tacho was doing, but I don't remember the engine changing pitch - so I don't think its the gearbox making funny changes.

So, I suspect that either the brake assist is doing odd things, or that I'm getting momentary lapses in the fuel supply to the engine - or perhaps something else that you guys might suggest?

I had a similar symptom once on a 190. Turned out to be the rear subframe bushes were shot, allowing a small movement forward when the drive was released. That was of course on a different generation of car, but might be that or engine /gearbox mountings.

 

[Dieselman]

I would check the lambda sensor switching frequency. It sounds like a 'lazy' lambda sensor reacting too slow. I would expect the switching frequency to be about 1 Hz at idle.

A slow switching lambda sensor will not show as a fault code on a W210.

Have a look inside the exhause tailpipe, you may see a sort of furry/sooty build up. This can be an indication of a lazy Lambda as it causes incomplete burn.

 

[Parrot of Doom]

Thanks for the input, but this is very definitely engine braking or wheel braking of some description.

Its only done it twice in the 2 months I've had the car, I have a feeling that its one of those niggles that will either raise its ugly head in a rather dramatic and expensive fashion, or it will just go away