Black smoke from ehaust

[LOAC]

I've got a Synergie 1.9 Turbo Diesel and the MOT is due next month.

The problem is I get a lot of black smoke from the exhaust above about 3,000 rpm and I'm worried about it failing becasue of that.

A few months back I was having problems accelerating, no power at all to speak of under 2,000 rpm and flat spots between 2,800 and 3,500 rpm. Plus I was getting quite a lot of black smoke at times.

In March I gave the car a service and changed the fuel filter, air filter and oil filter, plus I had a good look at the vacuum pipes and found that a short pipe (about 2.5 inches long) underneath the engine connected to a valve on the exhaust was persished and split. It was a real pain in the neck to get to, but I changed it and it transformed everything! Very smooth acceleration and no flat spots.

I took it over to Germany and it hit 110 mph on the autobahn, not bad I thought for a people carrier!

Then the fuel prices went through the roof and since then I've been driving round extremely carefully, not exceeding 2,500 rpm, and keeping it below 60 mph on the motorway. Fuel economy has been great, 45 mpg, about 10 mpg more than my normal driving style, but I've noticed that it's a bit hesitant below 2,000 rpm and I'm getting a lot of black smoke if I do rev it.

Do I need to adjust the mixture ratio and if so, how? Or should I do some kind of decoke?

LOAC

[myglaren]

Try a bottle of Forte Diesel System Cleaner - around £13 at an independent parts shop.

Then an Italian tune-up.

Run it down a motorway for around twenty miles at the maximum legal speed. Faster would be better but inadvisable if you want to keep your licence.

Make it WORK, it will do it a power of good and while the MPG will drop through the floor in the short term, the rewards will persist over the longer term.

My economy was crap, four miles to work in the a.m., four miles home at night, punctuated by the odd trip to the shops a mile away. It was hardly worth having a car.

A dose of Forte DSC and a 600 mile round trip, sometimes at greater speeds than required by law, where safe to do so, vastly improved the MPG and the responsiveness of the engine.

You personally observed the improvement that autobahn driving bestowed, you have talked yourself into it

[LOAC]

Would you put that in the fuel tank, or directly into the fuel filter housing as I've seen recommended in a few posts?

LOAC

[myglaren]

I'd be too skeered to dump it in the filter. I added it to the (empty) tank at the filling station then filled up the tank to the brim.

Might be more effective to add less fuel, I don't know. Seemed to work for me though.

I think the workout will be the most effective part for you, the injector cleaner being mostly automotive chicken soup. Still worth a shot though.

[lexi]

I am dubious about putting it neat into the filter. These treatments are very strong solvents and may have an affect on any rubber in IP.

The Millers diesel treatment I use is absolutely stinkingly strong and volatile. If it gets flushed with diesel a minute after it may be ok.......not sure myself.