Over fuelling

[AJC]

On the way home on Friday the car was fine for about the first half mile or so but then started to pop and bang at idle or slow speed, pick up the revs and it seemed to go or was less evident. The power was there and it did not seem to be over warm but I only travelled abut 5 miles, the tick over was about 1000-1100 and would fluctuate between the two. I had a quick look Saturday cleaned the stepper as I have had a couple of idling issues in the past then re-set the ECU. Took it for a spin but no change also there is a black build-up in the exhaust confirming the over fuelling. The car is a 500 with pre cats out and a sleeved exhaust, all new plugs, rota arm etc 6mths ago.
Also I was intending at some point to buy an ECU error code reader I may have to get it sooner than I thought?
Any help or ideas on the problem appreciated

[steve-V8s]

Could be loads of things, suggest you get it somewhere that has an exhaust gas analyser (almost any garage and all MOT places ) and get them to do a print out of what you have then post the results on this thread. You may find a bit more help with diagnosis if we have some data to work on.

In the meantime, have you cleaned / replaced the air filter recently ? does the temperature gauge work and settle at the normal point? does the Speedo read normally ?

If it really is over fuelling perhaps an injector is sticking open or the ECU is getting wrong temperature or speed info. It could be that the correct fuel is going in but it is not being burnt because you have a missing spark or two.

[FlipFlopGriff]

Have you access to a spare air flow meter you could swap. Easy job and possible cause.
We had one go recently, over fuelling, running gardually got worse until it died and couldn't start it.
FFG

[dumbfunk]

I had this issue coming back from Le Mans and it progressed from a sooty exhaust to a ride in a breakdown truck. Turned out to be a sticking fuel pressure regulator and £50 later I was good to go.


dumbfunk

[GreenV8S]

I wouldn't put too much faith in the exhaust colour. Do you smell unburned petrol coming out the back?

[Smuggling Sam]

Had the same problem myself, just picked it up, booted it(when warm!) and a cloud of smoke came out the back. Yes could smell petrol, turned out to be the throttle body/pot(not sure) needed adjusting. Dave Porter sorted it out.

[AJC]

I have no parts to try but will try all electrical connections on the engine etc and cleaning the air flow meter. The car does not smell of unburnt fuel but it has in the past, say if I reverse the car up the drive into the garage when cold, and could recently be a pig to tick over when doing this from cold, but not going for a drive from cold? If anything when I had a smell at the tailpipes after the engine was shut off there was a smell a bit like a spent firework? I would say it was getting up to temperature quicker Friday on the way home and when I took it for a quick run after the ECU re-set and getting hotter than usual but as they were both short runs I cannot say the temp was over the top. The Speedo seemed about right and it did not seem down on power as I did bring the revs up whilst out testing and it pulled fine. I will try a few bits myself through the week but I don’t get much time apart from the weekends to tinker.