binksy 73

HELP i have a sti version 5 impreza which is struggling to run on tick over and drive at low speed ie 1500 rpm-3500rpm. It is also kicking out black smoke and smells horrid the exhaust is covered in black soot. It is using feul at a unbeleivable rate and drives like it has a miss fire or flat spots but once the turbo comes in its fine and normal no loss of power.I have changed the air maf sensor for a new one which seemed better but after a drive retuned back to how it was.I have changed the o2 lamda sensor for a different one but car still the same,when you put your hand over the exhaust there is black soot which i think is unburnt fuel coming out of exhaust must be as have had flames out the back.Have taken out spark plugs and number 2 and 4 are the same colour with a bit of sooting up but numbers 1 and 3 are black and sooty so problem is on right bank of engine. Car has been sort of smoking a little for about a week or so but not that bad as did not think it was car, some have said it could be E.C.U fault or fuel pressure regulator air/fuel raito meter in rich zone on tick over when normally is flicking around,car was serviced 1200 miles ago it also has full de-cat exhaust and induction kit, any ideas please let me know.

greasemonkey

More questions than answers for you here, but your response to the following should help you/us zero in on the cause of the problem:

Did this start happening all of a sudden, like one minute it was driveable, the next buggered, or has the problem developed a little more gradually?

Was its onset related to the addition of the exhaust, induction kit, or any other bits? Was the lambda sensor you fitted a brand new, genuine Subaru one?

Have you tried starting the engine with the lambda sensor disconnected, and if so, was there any difference?

Have you tried putting the ECU in Read Memory mode to see if there are any stored DTC events, and if no errors were reported, did you try resetting the ECU afterward?

binksy 73

The car has been on subaru select monitor but no fault codes were found,probelm has come on gradually not due to exhaust or indution kit,lamda sensor was of a car in work shop not new but deemed to be ok not tryed running car without lamda sensor in and not reset cars memory but car has had lumpy tick over for some time just thought it was maf sensor on its way out,but car has gone into over boost on a few occassions last time on sunday but problem started after i let the engine brake me down a steep hill revs went upto 4000 rpm only, wouldn't have thought that could have bust it but problem came on next morning! Steve

The_Judge

Certainly sounds like some sort of closed loop AFR problem. You say an AFR gauge shows a static rich reading on tickover? As you say, it should flick about all over the place. I'd suggest getting another lambda on there, just to rule that out.

The fact it's OK when open loop would indicate the MAF/ECU/fuelling is OK. An ECU reset wouldn't hurt though.

Is your air filter OK? Just a thought. Other than that, get your spark plugs changed...

binksy 73

The maf sensor has been changed and car still ran bad,also have swapped the lambda sensor car still the same, plugs were changed at sevice which was 60,000 miles and 1,200 miles ago.The plugs for cylinders 1 and 3 are sooted up badly, were car is serviced say try checking injector seals and injectors themselvesthey may be leaking. Steve.

greasemonkey

Stuck/leaking injectors are one of the things that crossed my mind, but in that case it's unlikely that the car would then apparently run perfectly under boost.

If the person using the Select Monitor actually knew what they were doing, they should have seen something fairly obviously wrong, whether it lambda readings not correlating to the obviously rich mixtures, or something else.

If you haven't yet done so, try starting the engine with the lambda sensor disconnected. Incidentally, is "where car is serviced" a franchised Subaru dealer/independent Subaru specialist, or simply your local garage?

Incidentally, when you had the plugs out, did you check that all four had been gapped correctly and were of the correct type?

Either way, the error you're experiencing sounds like it needs specialist knowledge to fix, and unfortunately we're simply not in a position to advise without being able to see the car. IIWY I'd take it to somewhere who genuinely knows these cars and get them to have a look.