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Wiring Woe's and Poor Ideling

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  • CorridaCorrida
    Post count: 9

    Hi, I just have to say first that I am so happy there is a forum dedicated to the Volvo 780, we could use all the information that there is. I have an 87′ that has only had two real problems but, they have been plaguing me for over a year. The first is the bad idle. When I start it, no matter if engine is hot or not, it idles very poorly. When it is moving, it seems to be in perfect health. This problem is only when it is staying still- like at a traffic light, the RPM’s fly up and down from 1,000 to 2000. I have replaced the fuel pump and filter, battery, wires and plugs, and the fuel injection relay- nothing has worked. I can’t figure it out and neither can the five mechanics I have taken it to. What am I missing?
    The second problem is causing me to fail inspection. When I turn the lights on, nothing works, taillights, headlights, signals, fog lights, absolutely nothing. I can only get them on if I hold the level for the high beams, then everything works. I have replaced the bulb failure sensor and it didn’t help. The previous owner did his handy work on the wiring for the lights with “speaker wire”- or so my mechanic said. I have a feeling it has to do with this but I can’t even begin to understand why in one day the lights would work, then turn off in a sec. How do I trouble shoot for this, I know nothing about electrics. GAH

    I love the Volvo 780 and I have spent many hours a day keeping mine looking good and running well. I am just at a dead end and could use some help.

    Viva the Volvo 780

    Johan VlagsmaJohan Vlagsma
    Post count: 108

    Hi Sean, I agree it is nice to have a dedicated spot for collecting everything 780 in one place. These are special cars and are becoming rare.
    As for your two problems, what engine does your car have? The idle problem I would first check the entire intake path for leaks. Check all hoses, gaskets etc. for tears, bad connections and other vacuum leaks. The electrical issue is weird, sounds like a problem with the connection to mass. It it almost looks like the high beams are connecting everything to mass. Any loose or broken wires near the mass points?

    Post count: 9

    My car has the PVR 280F. The engine seems very strong and responses nicely but when in idle it can stall. Thank you very much for your input and I will look into hoses and vacuums, it would make a lot of sense if it’s one of those items- my fuel economy seems normal. I will take a look at the mass, not knowing where to look can make this issue impossible. My mechanic adviced me to buy a new harness just to help with trouble shooting.


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