1990 Volvo 760 Turbo: Black smoke when Turbo kicks in

My 1990 Volvo 760 Turbo (Intercooler) has weak accelleration and billows black smoke when the Turbo kicks in, especially under load up a steep hill (but also when accellerating by putting the gas pedal down to the floor on the freeway).

Any ideas on what might be wrong, and how to fix it?

Thanks, Wolfgang Santa Barbara, CA

Reply to
mot12345
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Sounds like you're leaking boost and the injection is injecting too much fuel for the air that's actually making it into the engine. Check all the rubber hoses between the turbo and the engine, particularly the couplers between the metal pipes and the intercooler. Pull them off and poke from inside with your fingers, I've seen them rip a flap that only opens up under boost.

Reply to
James Sweet

yep...i agree w/james...porb a broken or cracked turbo hose...check the big ones 1st...have a friend sit in the car and "punch it" and let off...see if you see a hose acting up....

ucsb...nice school....great location...how are things in sb county? i spent 50% of my youth in that area...what are you studying?

Reply to
~^ beancounter ~^

I doubt it is a torn turbo hose - those give symptoms of being normal until a moderate amount of throttle is called for, then the turbo starts spinning (even when the throttle keeps the boost from getting to the manifold) and the mixture goes *way* rich (as the others have noted) and the power drops like a stone... but it doesn't start running right until the engine has idled down and the turbo has spun down. It produces an odd "fold-back" throttle feel - just backing off a bit doesn't help; you have to take your foot off completely for a few seconds to go again. Going up hills is very difficult.

Our '85 765T did the black smoke and poor power under boost for a couple years before I stumbled on the problem. The cylinder head temp sensor under the manifold branch between the #3 and #4 cylinder - not visible without a mirror - was making intermittent contact. (It started a couple months after I changed the engine harness, but I didn't make the connection between the two events.) Try reseating the connector. It has a press-to-release wire spring latch and can be reached by sticking your arm way back past the throttle body. It isn't terribly hard to work with once you get your fingers on it. Ours occasionally has to be reseated still, but it has been over a year since the last time.

Mike

Reply to
Michael Pardee

Just how much black smoke and how poorly the engine runs under boost depends on the size of the hole. My neighbour's 760 turbo had a 1/2" rip in one of the short hoses at the intercooler, it still made some power under boost, but also made a huge amount of black smoke. The rip was on the under side, where oil pooled and was very hard to see.

Reply to
Mike F

those turbo hoses cost an arm and a leg....

(if you need to replace them)....

Reply to
~^ beancounter ~^

The standard straight ones aren't too bad, they're easy to get aftermarket. If you need one of the custom formed ones though... ouch!

Reply to
James Sweet

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