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Old 06-24-2013, 05:38 PM   #19
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Join Date: Jan 2007
Location: Vero Beach

Originally Posted by Bensin View Post
Sounds like you have more than one problem. I don't have OBD on my 86 car, so I don't know codes. I don't know typical causes of backfire, but it makes me think ignition. Are your spark plug wires good? Distributor cap and rotor good?

?? Need some more clarification on this style, or even better, some photos.

By the way, the BOV is also stock for Volvo's with Garretts, it's just they way it's connected isn't standard.

That's the hose I have. It's got a two-wire plug in it to heat the air going to the crankcase vent. I read somewhere that it was to help de-ice the system in cold weather, but I don't know if that's entirely true or if removing it would be a problem.

Spark plug wires are in good shape, cap and rotor looked good when I first drove the car a few months ago although I will check them again next time I get to work on the car. I actually busted the coil wire when I first got the car and replaced it with a brand new one I had as a spare for my other 740, so I know that one at least isn't the problem.

The intake hose is definitely creased in a way that will encourage it to collapse and seems to be getting worse, so I'm putting together a parts list to replace it with something more durable. The only holdups are figuring out the crankcase vent setup and actually having the money to put it together. If I can just ignore the heater in that tube I can just add another regular port and be done.

The power loss problem seems to be almost entirely absent from a cold start and gets progressively worse over a long drive, which I think is consistent with the hose collapsing as it gets warmer. I feel pretty stupid for ignoring the possibility before.
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