posted on Jan, 26 2008 @ 04:27 AM
Check the oil level in your engine.
If it's overfilled this can get into the combustion chambers and seeing as diesel is an oil, the glow plugs will ignite the engine oil and cause the
running on effect.
Similarly, keep an eye on the oil level as you might have worn valve stem seals or piston rings. That would let oil in too.
Will also raise the engine revs as there is no control over engine oil being burnt.
but this does not explain why putting your foot down will give you 3k revs yet only a slow speed.
The black smoke is mostly soot. All diesels cough up black smoke at some point, particularly on start up. You might have a faulty exhaust system.
Check for blowing or damage, like a crushed/blocked section.
Back pressure in exhausts is as important as letting the gasses escape. Too much back pressure and the engine chokes.
Try changing your glow plugs. They might need replacing.
The high revs/low speed is a bit odd. I assume you've got an automatic box.
It could be the catalytic convertor rather than the box itself.
It's the same principle as a slipping clutch. You could have all the revs you like, but with a worn clutch/convetor, you're only going to go so
edit to add; just had a thought.. have you got one of those gear boxes that you can select high or low gears (as used in some 4x4 vehicles like land
rovers) aside from the main gears?
Might be stuck in low if you have.
[edit on 26-1-2008 by Extralien]