Black smoke

skendrick · Dec 21, 2005

Hi,

My car has been running well recently until last week when I overtook an old fart doing 30 in a 60, the car coughed and since then chucked out black smoke on heavy acceleration. My specialist said the exhaust is clogged up and needs a good run which I have done. The car seems a little better but is still throwing out black smoke.
The car is due for a service but was told it would be better to rectify this problem first.

Any thoughts or similar problems.

Steve

1988 944 Turbo

John Sims · Dec 21, 2005

For a "good run" I would read "give it a damn good thrashing". Fill it up with Optimax and then drive it like you stole it, until almost all the fuel is gone (it shouldn't take more than a couple of hours if you really try [

]).

If it ain't boosting, you ain't trying.

You should then get the exhaust nice and hot and blow out any cobwebs. If it is something more serious, at least it should then come to the surface so you know what you are dealing with.

Big Dave · Dec 21, 2005

"If it is something more serious,", like a blown head gasket ... After giving it beans.[

][

]
I think ide get it serviced b4 giving it a full blat.....[

][

]

andymarsden1 · Dec 21, 2005

I did that to mine a while ago and all the exhaust baffles came out[&:] oops........

Andy

944Turbo · Dec 21, 2005

Bet its a boost leak, one of the larger rubber hoses would be my guess.
Tony

skendrick · Dec 21, 2005

Thanks for your input, I will do a main check over xmas myself and see if it gets better. I have checked the hoses (but will check again) around the engine and replaced the DME relay with my spare. I will change the air filter and see what happens.

I will let you know what happens

Steve
1988 944 Turbo

Diver944 · Dec 21, 2005

My amateur guess would also be a loose boost or vacuum pipe, but check all the simple things like plugs and leads too in case one cylinder is not igniting properly.

Apart from the smoke does the car seem to run normally?

My S2 had the same symptoms a few years ago and it was the engine temp sensor. It had failed and the ECU always thought the engine was cold so was running like it had the choke out.

944cabby · Dec 21, 2005

My old '83 924 lux did it once coming down off the plynlimon mountains.
Basically started to pump out dark, thick plumes of smoke so bad that people were flashing their lights at me all the way home.She drove fine though and for a further 20 miles or so.For the next couple of short drives it carried on pumping it out albeit not as much and i thought the engine was knackered as at the time i had been using it regularly for an 80m found trip.Then it cleared up as quick as it came and never happened again.

berg944 · Dec 21, 2005

Sounds like it went when on boost, Check the intercooler pipes.

Mine did a very big cough (the sort that leaves a lump in your pants) when the intercooler disconnected itself.

It overfueled until I found the loose pipe.

Mike[:'(]

skendrick · Dec 21, 2005

The car seems to run at it's worst when cold and gets better as it gets hotter. On my long 100m run the temperature never got too hot and I have decided it isn't the exhaust pipe, so I will check all the pipes.

The car does run normal until I start to accelerate hard, black smoke (lots of) and a bit of hesitation going on.

Steve

John Maddox · Dec 22, 2005

Probably overfuelling. Try changing the fuel pressure regulator on the fuel rail as this is only £35 and a 5 minute diy job.

Mine was running rich and this cured it completely.

John Sims · Dec 22, 2005

Oh go on then - I will have to agree that black smoke could well be (is) down to over fueling - something I know a lot about with a Link AFM conversion (available from ProMAX Motorsport [

]). Have a good chase around all of the pressurised pipes and see what comes to light first.....though I think you would have had more fun with my initial prognosis (and would have been able to produce some great flames [8D]).

skendrick · Dec 22, 2005

Are the K&N air filters worth the extra £40 or should I stick with the standard?

Guest · Dec 22, 2005

save it.

Save that a few times more and then you can stick a K&N on a MAF and actually have something that'll give you a HP increase you can feel. [

]

John Sims · Dec 22, 2005

ORIGINAL: pikey7
save it.
Save that a few times more and then you can stick a K&N on a MAF and actually have something that'll give you a HP increase you can feel. []

I think you will find K&N panel filters are on special offer from ProMAX Motorsport at the moment. But if you did want to go for MAF you could get that supplied and fitted by ProMAX Motorsport.

.....thought I'd get in first this time [

]

skendrick · Jan 3, 2006

The car is at the garage today being serviced and hoping to resolve the problem, but I would like to thank Andrew from Promaxsport for dropping off the air filter and vacume kit on xmas morning. I had to stop myself opening this before I finished opening my presents.

Steve
1988 944 Turbo

Diver944 · Jan 3, 2006

ORIGINAL: skendrick

thank Andrew from Promaxsport for dropping off the air filter and vacume kit on xmas morning.

Blimey! Was he dressed up in a red Santa suit? [

]

On 2nd thoughts I don't want that picture in my mind [&:]

sawood12 · Jan 3, 2006

My experience with black smoke (on other cars - no issues with the 944 yet touch wood!) has usually been down to a split in the large dia rubber inlet manifold hose. I doubt it will be a loose intercooler pipe as when my intercooler pipe was loose the car didn't make any power above 1 bar absolute (i.e. no boost) and you could hear an almighty wooshing noise due to the air being blown out of the leaking intercooler hose. If one of your vacuum hoses was leaking you would probably have problems at idle as well. But black smoke is definately unburned fuel i.e. soot so you've either got an air leak downstream of the AFM somewhere or there is a problem with the fuel side of things which is causing excess fuel being squirted into the cylinders. If your car is running rich you can check the spark plugs - they will have a black sooty (but dry) deposit on them instead of a nice brown colour coating. If you are getting oil into the cylinder you will have a black oily deposit on the spark plugs - it's at this point you should feel no shame in breaking down in tears.

skendrick · Jan 5, 2006

The car was serviced yesterday and yes the spark plugs were black, had the ecu and air sensor checked out, both ok. The car was taken to the MOT place where it decided to stop and refuse to start again, they had to push it off the ramp and I am about to call the AA to get it back to the workshop to find out what the problem is?

Steve
1988 944 Turbo