Very little low end power and lots of smoke - expert advice needed

[metallurch]

Hi everyone,

I have a 2003 model C220 CDi and I'm having serious problems with it. When the engine is started from cold it shudders quite violently for the first few seconds and then stalls. Usually on the 2nd start it shudders and picks up. If you push the accelerator all the way to the floor on the first start it will prevent it from stalling but the revs don't climb, it just shudders violently for about 10 seconds like its barely able to run. The odd thing is that after about 10 seconds it seems to idle ok and revs will climb as you would expect.

When I attempt to set off, in either D or R the car hardly moves. Even with my foot to the floor it will crawl very slowly, I don't get any power from it until it reaches about 1300-1400 RPM, during this stage it will pump out a huge cloud of black smoke. Once it is past that stage and on the boost the car drives perfectly fine, so really the only issue is setting off from a standstill. Once rolling the car behaves normally, no power issues, gear changes are smooth and It'll easily cruise at 90mph on the motorway with no excessive smoke that I can see.

So having a small amount of technical knowledge I've done a bit of work myself, and here's what I know so far:

The EGR valve is not clogged, and there are no issues with the actuator. I've cleaned it and with the intake hose removed I can see the valve moving freely while the engine is running.

The intake manifold contains a bit of gunk as you would expect for a car on 110,000 miles but none of the channels are blocked and the swirl flaps move freely.

In some of the gunk lining the intake ports on the cylinder head I found a couple of small metal shards (about 2-4mm), this was found in 2 of the intake ports. I have no idea where it could have come from as the air filter is in good condition and the compressor on the turbo looks perfectly normal. Not to mention that if the turbo was missing chunks if its compressor wheel it probably wouldn't work too well.

The car shows up no fault codes.


I was thinking about pulling some injectors out to check out the state of the pistons and valves with a fiber optic camera but I'm concerned that if I let air into the common rail fuel system it might not start up when I put it back together. If anyone out there has any advice on what I should do next it would be much appreciated, I've pretty much reached the limit of my knowledge.

Thanks.

 

[turbopete]

sounds as though you could have an air leak (air getting into the fuel) which is commonly cured by replacing the o rings on the plastic fuel pipes. regarding poor performance/smoke does it do this at ANY time or just after startup? you may have an injector fault if it does it at ANY time.

Metal shards doesnt sound too good though. are the swirl flaps secure?

 

[metallurch]

Good point, I'll see if I can see any bubbles in the tube when its running. If it was sucking air in though would that not have an impact on performance at high revs, presumably the more fuel its sucking through the more air would go with it?

The power issue when setting off is pretty much all the time although it does get slightly better when the engine is up to temperature, but not by much, you wouldn't want to hit a busy roundabout in it that's for sure.

The metal shards I found are a complete mystery to me, I've cleaned out the manifold best I can and the swirl flaps look fine. I've yet to pull the intercooler off and inspect that but it looks fine from the outside, the turbo looks and works fine. Not a clue where they've come from but that's why I want to see inside the cylinders, I figure if anythings been sucked in there and marked the cylinder lining or pistons then its probably not worth bothering with. I'm not too keen on the idea of dismantling the fuel system though, do you know if it will just bleed itself out? I've heard that common rail systems can be a nightmare to get running again when they have air in them.

 

[M80]

The fuel system would normally bleed itself. If there is that much air being sucked in it might well show fuel leaking under pressure ??
I would disconnect each injector in turn, while running, to see if one makes no difference.

 

[oigle]

Good point, I'll see if I can see any bubbles in the tube when its running. If it was sucking air in though would that not have an impact on performance at high revs, presumably the more fuel its sucking through the more air would go with it?

The power issue when setting off is pretty much all the time although it does get slightly better when the engine is up to temperature, but not by much, you wouldn't want to hit a busy roundabout in it that's for sure.

The metal shards I found are a complete mystery to me, I've cleaned out the manifold best I can and the swirl flaps look fine. I've yet to pull the intercooler off and inspect that but it looks fine from the outside, the turbo looks and works fine. Not a clue where they've come from but that's why I want to see inside the cylinders, I figure if anythings been sucked in there and marked the cylinder lining or pistons then its probably not worth bothering with. I'm not too keen on the idea of dismantling the fuel system though, do you know if it will just bleed itself out? I've heard that common rail systems can be a nightmare to get running again when they have air in them.

I'd be much more concerned about possible damage to the exhaust vanes in the turbo than a few marks inside the cylinder.

 

[turbopete]

Good point, I'll see if I can see any bubbles in the tube when its running. If it was sucking air in though would that not have an impact on performance at high revs, presumably the more fuel its sucking through the more air would go with it?

usually the air is only evident on start-up when the car has stood for a fair period/overnight. usually once started, the car will drive perfectly, with no adverse effect on performance. if you are able, try parking the car facing downhill overnight and see if it starts easier the next day (the weight of the fuel allows less air into the lines as the entire contents of the tank are pushing against the seals, is my theory of why this seems to work)

 

[metallurch]

Cheers for the advice guys, tried a couple of things at weekend. Starting after the car has been parked on a hill doesn't seem to make much difference, it didn't stall on that particular occasion but it did its usual shuddering thing. I also tried unplugging the injectors while the engine was running, and as soon as I unplug any of them the engine cuts out. I'm guessing this is by design and the engine management just wont let it run with an injector unplugged?