My 87 760 turbo started bucking at cruize speed the other day. The Tach goes from 2500 RPM to 1000 then back up. If I stomp on the gas it'll hessitate and then straighten out and drive OK for a while. It does not "hessitate and die " when all this is goign on. I can baby it at between 1000 - 1500 RPM ( 20 mph) and get it home. SO far Ive replaced fuel filter, AMM and air temperature valve. I've been reading FAQ. It talks about fuel pump regulator, a soft turbo hose and possibly the pre fuel pump in teh gas tank. I'm reluctant to fill the tank and see if it drives OK with a full tank, cause if it does, then I have a full tank of 12 gallons of gas to deal with when swaping out that tank fuel pump. Any comments on my my next step should be?

Thanks in advance for any info

My intuition makes me favor the Hall sensor. Usually, the air intake leak happens when accelerating, not at steady speed without any prompting.

Does it miss and buck while limping it home? The Fuel Pressure Regulator (FPR) usually fails and stays failed - doesn't go back and forth. You can just add a few gallons of gas to the tank - or try driving in big circles or braking semi-hard for a few hundred feet (or maybe parking on a hill) to get the gas to move away from the pickup tube.

Is there anything that consistently happens when this problem appears? Like cold weather, rain, having all the accessories on or something else?
What makes it disappear?

Good Luck


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1990 740 Turbo, on its way to stock specs, maybe beyond

Soft turbo hose collapsing?(FAQs has a homemade pressure test to check hoses, etc)
Check hall sensor wiring at base of distributor for shorting out.
How low is your fuel level? The short pickup hose issues normally shows up in turns below quarter of a tank.
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Post Back. That's whats makes this forum work.

O Kay. It's been a week since I filled the gas tank and in 93 miles it hasn't bucked a bit. The other curious thing is when I unscrewed the GAS CAP, I heard a distinctive PSSSFT.And it brought to mind my highschool auto mechanics teacher telling us how a gas cap that doesnt vent will creat a vacuum inside the gas tank that will starve a carberator.


So right now, I am driving at just below 3/4 tank with a gas cap that isnt screwed on tight and if she dosnt buck when close to 1/4 i'll buy a new gas cap. If she bucks at half, I'll buy an in-tank fuel pump