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740 Bucks Like a Bronco 700 1988

posted by  Jolly on  Tue Jul 27 05:08 CST 2004
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Hi Everyone!

I have 740GLE Wagon 5spd. Recently, the car has been bucking while driving down the road. It seems to have gotten gradually worse. I notice the tach starts flying all over the place when this happens.

The bucking just kind of happens randomly for a few minutes, and then will go away for a bit. It seems to happen more frequently on surface streets (more acceleration) than while on the highway. If I try to accelerate while the car is bucking, I usually get no reaction from the car, and if it happens while driving up a hill, I have to pull over.

It seems as though there are no problems whatsoever when the car is just idling. However, if the bucking happens, and I push the clutch in, the car will continue having this fit.

I have read through the FAQ and nothing really seems to correspond exactly with this particular problem (unless I overlooked it), except maybe a bad knock senser. Would a main fuel pump that is going bad cause this to happen?

Any help would be appreciated!

Best Regards,
Niclas







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    740 Bucks Like a Bronco 700 1988

    posted by  Rtilghman on  Wed Jul 28 05:25 CST 2004
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    1. Hall effect or rpm sensor

    2. General ignition fault

    3. Bad Fuel Pressure Regulator

    Next time it happens see if the tach drops to zero at any point when its jumping around (like pinned dead at the bottom of the tach while you're moving). If so its almots undoubtedly the ignition system and the hall or rpm sensor, and I would start there and work my way back to the coil, plugs and plug wires, and the ignition control unit on the driver's side fender.

    You can read more about all this in the FAQ under the ignition and performance sections.

    -rt








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    740 Bucks Like a Bronco 700 1988

    posted by  Volvo Dan on  Wed Jul 28 04:28 CST 2004
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    I had a similar problem with my '85 740, it was a bad wiring harness, the fuel injectors were acting up b/c of it...








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      740 Bucks Like a Bronco-Look Harness & Intake 700 1988

      posted by  servano on  Sat Jul 31 05:10 CST 2004
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      My 87-740T had similar probs with surging. Harness looked exposed in some areas but not that bad. Then, with Board guide in hand, I removed the sucker to check it all out and the thing practicaly disintegrated. The old timer I did this with started laughing and stated that Volvo's must be able to operate without a harness because mine was useless.
      That cleared up almost alot of probs. The last of the bucking/idle probs was caused by failing Fuel Pump Regulator. I used the house check test on it and it seemed ok but since mine was orig I replaced it. That solved the last problem.
      --
      87-740T (B230FT w/Garrett) 142k







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