GabiOsz

I have been having trouble with my car dieseling or running-on when swithing off the engine. The car spltters and turns over for a few seconds when I switch off the engine, this happens more often when the engine is hot. Occasionally there is trouble starting the car if it has run-on when last shut off.

I have been told that it can be caused by carbon buildup which stays hot. How do I decarbonise the engine without taking it to pieces? is there anything else that would cause such a problem?

I have tried the two major Super unleaded fuels (Shell Optimax & BP Ultimate) and they both do the same.

GratefulJED

I saw that you removed the chip - could that have something to do with it? Perhaps a good old fashioned Italian tune up with some ventil sauber and techron as well. Good Luck

GabiOsz

The chip has gone for now, due to a strange clattering while accelrating under load, which seems to have stopped now. However I can't get ventil sauber and techron in the UK, and don't know which brands available here will actually work.

Incidentally the fuel treatments I have used in the past treat 50 - 60 liters of fuel and I have obviously over diluted them in a full tank, what is the capacity of the tank in a 993 including the reserve?

Monique

I have a suggestion which worked in high compression engines in the late 60's... don't ask.

1. Get a thoroughly clean spray bottle. Remove your air filter.

2. Warm up your engine.

3. Have someone hold 2500 rpm and spray the water mist into the air intake. Stay clear of the exhaust pipes.. there will be lots of s$#% come out.

Good luck

GabiOsz

Monique, what do you mean, just a water mister?

how does this work?

JohnJL

I've heard that on the FJ40 list too, though much debate ensued about the merit and dangers....

GabiOsz

Dangers!? what dangers?

JohnJL

some stories about cracking intake manifolds and damaging valves by squirting cold water on hot parts.

someone also speculated about hydro-locking, but I gotta believe you'd have to squirt a LOT of water in there to get that. i wouldn't want to find out though.

this is an entirely different vehicle we're talking about and someone is going to come back with much more germane answer i am sure, but on vehicles I've dealt with in the past this dieseling has had to do with faulty fuel shutoff/idle valves.

Now I'll stop before I embarass myself ;-)

Terry Adams

I used to impress friends in the 70's with the glass of water poured slowly down the air intake stunt, and someone holding a white cloth over the exhaust. I think Steve Weiner said there could be valve or other damage caused by carbon chunks breaking off.

chris walrod

Before the days of O2 sensors, we used automatic transmission fluid, poored into a running engine to decarbonize. Wouldnt do this nowadays as it would damage MAF/MAP/O2 sensors.

Have heard good results with more modern methods, like the 'motorvac' procedure. Otherwise its back to the old fashioned teardown and reseal option..

JasonAndreas

Chris,
If you pulled the catalytic converters off and fed water into the engine through a vacuum hose would that be less troublesome?

Monique

I think the motorvac is more refined.

GabiOsz

How much is motor vac to have done? is it any good?

Incidently How do I change the O2 Sensor? and how much is the part?

Oh, and once again... the fuel treatments I have used in the past treat 50 - 60 liters of fuel and I have obviously over diluted them in a full tank, what is the capacity of the tank in a 993 including the reserve?

Monique

B4 someone else buttons you.

Gas tank is either 72 liters with 10 liter reserve or 92 liters with 12.5 liter reserve. Easy to distinguish. If you can put a set of golf clubs in your boot, you have a 72 liter.

Re spray bottle... only a mist. You should not pour water into your manifold. Hope you knew this... But motorvac is the better idea.

GabiOsz

Is that a total of 82 liters or 72 including a 10 liter reserve? so I should dose the tank with fuel system cleaner when its just under 3/4 full?

Anyone know who does this motorvac in the UK?