Hi guys n gals,
I was wondering if anyone could give me a few pointers - im not used
to turbo weasels. :)
My brothers car recently went for its MOT. The guy in the station
switched the engine on, walked away and the engine revved through the
roof. The test guy ran to the car to switch it off but when he did it
it didnt turn off immediately. Obviously it failed the MOT, and had to
be towed home as it keeps doing it. This is the first fault its had,
but seems terminal - its going to be scrapped if i cant fix it, which
would be a shame as its in good nick other than that. I'm hoping the
rev-limiter bouncing hasnt done any harm? Anyone with any experience?
Brother says it runs smoothly when it revs through the roof, but
sounds pretty clackety and smells rich. Can anyone point me to common
faults that might cause this??
CoyoteBoy ( email@example.com) gurgled happily, sounding much like
they were saying :
Really silly question - the throttle pedal and cable are both moving freely
- and more importantly, returning to rest on the spring? The MOT man hasn't
done something silly like manage to wedge a floor mat onto the loud pedal,
Other than that, check the oil level, air filter and the breather circuitry
- it *might* be somehow sucking engine oil in, causing it to run - don't
forget that it's the fuel that's throttle-restricted on a diseasel, not the
air. Did they do anything else, like a service or any other maintenance or
Since no-load revving a diseasel to the limiter is part of the MOT, it
certainly shouldn't do.
As far as we can see the throttle pedal/cable is fine, but its worth a
double checking I guess - that'd be a nice cheap solution!
The car hasnt had any service work done on it recently, about 6 months
ago it had filter etc but it has been sat unused for some weeks as the
seat needed replacing, so maybe something got stuck with lack of use.
Does the system have an ECU or is it all vacuum/mechanical control? Is
a fault with the fuel pump likely to cause this sort of fault? Is the
throttle on the fuel in the pump or seperate do you know?
I'm glad to hear no-load revving doesnt hurt it, id have died if my car
had hit the limiter unloaded lol :)
James - a little happier
Latest communication from my brother says:
"The throttle cable is fine, but the pump throttle arm felt a little
tight / gritty (without cable attached)
Air filter isnt that old, but surely doesn't cause that all of a
sudden, Oil level - again has used some but not massively or more than
normal, Pulled fine before taking it to them eitherway without smoke!
More than a bit clackety - sounds like my valves are sat on the
Will check vacuum hoses - nothing looked out of place, although a
breather hose has split but has been a little for a while with no
problems. (special part taper hose)"
Thanks for the thoughts so far.
Latest information - whipped off the turbo-IC hose - properly lined
with sump oil :( took off the breather that feeds from the top of the
dipstick 'pot' into the intake before the turbo and nothing comes out
of that when running. Fire up without the turbo hose on and a nice mist
of black oil coats your face :( 99% certain its a blown turbo then.
The loud knock it gets is very strange though i must admit - seems to
be a slightly random very loud deisel knock (like someone is randomly
slamming the block with a hammer)- just once or twice in a second then
nothing for 2-3 seconds. Doesnt vanish under load but smooths out to
some extent under revs. Other than that one nasty knock noise it seems
sweet so i may try to find a replacement turbo and give it a shot. Are
the turbos common faults on these? we've been offered one for £30
from a local garage. Should be a simple-ish job - easier than on my
celica where it meant taking the whole front of the car off virtually.
Cheers all round for those who helped.
You give no details of the vehicle, what year, and how many miles? This is
What colour smoke came out when it revved. If it is burning breather oil,
due to a very worn engine, then it would be bluish white smoke. If it looked
normal to sooty, then it is probably some problem with overfuelling.
However, the cut off solenoid should then have stopped it.
Remember that the throttle control is only on the pump, and has no effext on
the air intake. Thus if the engine can find any other fuel to burn, it will
run on. This includes oil in a worn engine.
:D Ta Adrian lol, but i did miss some info i must admit.
Its '94 i think, no more than 90K miles, in good shape, pulled well
with nothing but light smoke on startup before this, light oil usage
before this - no idea now as it cant be driven safely. Now it's
chucking out what my brother describes as 'blue/black/grey' smoke lol
when it goes nuts, and now its idling ok (if noisy, better described as
a normal diesel sound but louder), but a touch on the loud pedal makes
it go skyward but in a smoother less rattly way.
runaway diesel syndrome:
And finally, a word about 'runaway diesels'. This is a nasty little problem
affect any diesel where the crankcase breather pipe feeds direct into the air
Land Rover turbodiesels are notorious for it, and I have seen it on 1.9
diesels as well. What happens is that on a worn engine, gases blow past the
the pistons and into the crankcase. They emerge from the crankcase breather
with oil mist from the crankcase, which feeds into the air intake. Now a diesel
quite happily on oil mist, and so the revs will increase as this extra 'fuel' is
The higher revs result in greater crankcase pressure, more oil mist is forced
the crankcase and sucked in to the engine, and a vicious circle is created.
Eventually the point is reached where the engine is generating enough oil mist
shutting off the supply of diesel by switching off the ignition will not stop
it. The engine
runs faster and faster, generating huge clouds of grey or black smoke, until it
If your engine starts to run away, you can sometimes stop it by selecting top
your right foot hard on the brake and letting the clutch out to try and stall
the engine. But
diesels generate a lot of torque, and if the clutch is weak, it will just slip.
In this case there
is nothing you can do other than abandon the car, retire to a safe distance and
wait for the
engine to explode. Do not under any circumstances open the bonnet - it isn't
worth the risk.
repeat: "The engine runs faster and faster, generating huge clouds of grey or
the clues are there, no ?
RT, yup, this possibility is under investigation as we speak (well, not
quite as its chucking it down with rain) and im hoping its that
simple, since this seems to be the only explanation people have im
guessing its so, but the engine is a lower milage, non-smoker,non-oil
consumer normally so it'll be hard to pinpoint i guess - no obvious
cause if the turbo isnt shot.
My main concern was how strong the fuel pump unit was, whether a
stiff/slightly gritty feeling action on the cam means it is shafted
inside, or if thats pretty unlikely.
Muchos thankyou-os :)
IIRC 90K yes, miles, and of the thousand variety :) Its certainly not a
high miler (unless im mistaking it with another ZX TD i know, one is
120K, one is 90K, but either way its only a young'un, and yes, got
history and is tidy/smooth enough to back it up)
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