W210 E320 CDi MAF + smoking

[Dave K]

My E320 CDi has destroyed a MAF within 1.5 years of replacing it. Ho hum. MB read the fault code out and confirmed my suspicions. They even tried another MAF to see if the situation improved..and it did (revs above 3000 and has low down grunt again). But, even with the new MAF fitted, it's still chucking out a fair bit of black smoke. It also suffers a sort of tinkling/clattering noise from the engine (although it can't be heard when revving in neutral or park - must need some load). MB reckon either blocked catalyst, clogged injectors, or faulty EGR. I've tried Millers to cure the tinkling/clattering (it's been going on for quite a while) but no perceivable difference. Do these injectors respond well to proper off car cleaning (ASNU type machine) or is replacement the only answer? Does anyone have any experience of the EGR system on these cars? I'd imagine replacement is straightforward but can it be blanked off (rather than disabling the actuator which would throw a fault code)? I expect all this will become apparent once I get stuck into it but just doing a bit of homework before unleashing the spanners on it.

 

[l5foye]

Maybe you already know but the MB computer can measure the pressure at each injector. It displays the acceptable range and beside it, shows the actual pressure. The results would confirm if injectors were clogged.

 

[Dave K]

Update : they substituted the injectors for new ones but it made no difference - smokes way too much (new MAF fitted). They found the EGR was seized - fitted a new one but made no real difference to the smoking. Compression test shows compression is OK on all cylinders. No stored fault codes so they are now totally bemused (they rely too much on fault codes).

Any ideas what can be causing it to smoke so much (it's black/brown smoke)? It's getting really expensive now !!!

 

[jeremytaylor]

When the EGR went on my 270 (same engine as yours with a cylinder lopped off) there was smoke at almost any revs.

Surprised that changing this and the injectors hasn't solved it. Sounds like it's still overfuelling. (I assume the air filter is OK).

 

[Dave K]

Air filter is fine (changed just a few weeks ago). I've even checked the inlet pipes for blockages but none found. I agree, something is making it overfuel like mad.

 

[andreas_t]

Have a look at my woes in this thread: http://www.mbclub.co.uk/forums/showthread.php?t=25791

 

[se97mlm]

Turbo...

 

[Dieselman]

Could be blowing off boost via a leak. This will cause air to pass the MAF so will fuel up but no power.
Connect a boost gauge.

 

[jgevers]

As above, and are you sure that the correct MAF was fitted.
Forinstance, fitting a VAG petrol MAF will have a faster voltage progression resulting in good low down power due to the car shooting past it's boost target and additional fuelling. Great but lot's of smoke and high EGTs.

Cheers

 

[Dave K]

Update : Fixed the smoking. Apparently they didn't replace the EGR - only cleaned it. In desparation, they took one off another customers car (naughty), fitted it on mine, and problem solved. They then got a brand new one in and compared it side by side with my old one. Apparently you can see that mine is "worn" i.e. doesn't seal properly despite the fact it's been cleaned. So, that's fixed that. I'm mighty p!ssed off that I didn't trust my own instincts and just fit a new EGR myself.

But........they say that there is still an issue with intermittent lack of power. When it's working right, it goes like a rocket. But it's occasionaly lethargic. I wonder if the new MAF (not genuine MB) is the cause? I'll update the thread when I know. Christ, this is gonna cost me!!!

 

[skemball]

im interested to know where the EGR valve is located - is it the silver coloured cylinder mounted horizontally and secured with 3 Torx screws into the side of the inlet manifold ?

My engine has 86k on it and does 'grumble' on hot engine idle - comes and goes

 

[l5foye]

Dave K - I think if I were you, I would be going to another garage. If the diagnostic equipment had been properly used in the first place, you would have been saved a lot of grief and possibly money. As I pointed out earlier, as an example, the equipment can determine whether or not the injectors are working properly; so why did the garage replace them ?

 

[Dave K]

I agree - this lot are flamming useless. Of course, use of a current sensing device (an oscilliscpe is ideal for this) can determine how well injectors are opening. What cannot be tested is how good the spray pattern is. The only surefire way to test is to test off the car. However, in this instance they simply went for substitation to see if it made a difference. It didn't so they put my old injectors back. Typical modern day mechanics these days - just keep replacing parts until the problem does away. No real trouble shooting/diagnostic skills at all.

Dave K - I think if I were you, I would be going to another garage. If the diagnostic equipment had been properly used in the first place, you would have been saved a lot of grief and possibly money. As I pointed out earlier, as an example, the equipment can determine whether or not the injectors are working properly; so why did the garage replace them ?

 

[MPK]

Ref: " tinkling/chattering noise" you mentioned in original post

Dave - My E300TD made a similar racket particularly at tickover.
Noise was akin to a 1p piece vibrating around bottom of the exhaust.
Over time - 18months, I got used to it but other folks would comment " Whats that noise from your engine mate ". I assumed the CAT.

After 18mths, the noise increased and power was consistantly down.
Bit the bullet and replaced with a genuine MB CAT.
That noise gone and power is up / fuel economy increased.

However - I have now noticed a different slight " knocking" type noise at tickover which dissappears when I rev slightly.
( Will start new thread on this subject rather than hi-hack yours.)

PS - Is their any way to clean / check the operation of the EGR ?

Best of luck Mike.

 

[Dave K]

The "tinkling/chattering" noise is not evident unless the engine is under some sort of load. I've had the car up on the ramps with the engine running checking for blowing exhaust or simillar. It's not really a mechanical noise - more of a combustion type noise. It's like pinking/pre-ignition sounds on a petrol engine. Doesn't happen when revving the car in neutral or park. It only happens when the engine is actually having to physically move the car along (i.e. load). I'll see if the noise is still there when I get the car back.

 

[Dave K]

Finally got it back today (I haven't driven it yet - it's still on the drive where they delivered it). The intermittent power loss was being caused by the brand new MAF I'd bought on eBay from "the.portland.group" which wasn't OEM. Beware of that one.

The bill was 25 hours at £95 p/h + new EGR @ £271 + VAT + one glow plug + a seal. Grand total = £2700. Needless to say, I showed by displeasure. I made them perfectly aware of the fact I considered that I'd paid for a training course for them. There was no need to remove the injectors and that cleaning the EGR and then looking at other causes had resulted in needless hours being spent on the job. We settled on £900.

 

[skemball]

I believe the pinking noise is normal for modern oil-burners. Mine does - especially noticeable when in a multi storey car park driving up the ramps.

I have heard its a a consequence of lean burn diesal engines -

 

[Dave K]

Car drives nicely with no smoke at all. Lovely. At last.

The clattery noise is still there Can be heard within the cockpit but not really evident from the engine bay (i.e. listening to the engine with the bonnet up). Clattering reduces dramatcially when the steering wheel is turned left or right during cornering etc. Bizarre !!!! It's almost as if there is a hole into the engine bay from the cockpit.

 

[DrNick]

That because there probably is! On my 99 E300 the rubber coupling/grommet that covers the steering column had a hole in one side, and this lets noise in. As you turn the wheel the grommet turns and doesn't let so much though. You can see this item under the bonnet where the steering column enters the engine bay. I stuffed a sock in mine! Peel back the carpet in the drivers footwell and this should give access. If the noise goes away/is reduced then a new coupling is the answer

Car drives nicely with no smoke at all. Lovely. At last.

The clattery noise is still there Can be heard within the cockpit but not really evident from the engine bay (i.e. listening to the engine with the bonnet up). Clattering reduces dramatcially when the steering wheel is turned left or right during cornering etc. Bizarre !!!! It's almost as if there is a hole into the engine bay from the cockpit.

 

[Dave K]

Ahhhhhhhhhhh. That sound promising. I'll check when Mrs. K returns with the moneypit.