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This post is going to be long, but I've got a lot of issues here and they may all be related, so please hang in there and give me your advice.
I purchased this 745 Turbo about 2 months ago. It was running great for the first month although I did notice a black cloud out the back under hard acceleration. I replaced the air filter, changed the oil, and installed a new oxygen sensor. The car uses oil, about a quart every 1000 miles. It was running fine, I didn't change anything, and then it started running crappy. When I say crappy, I am talking performance wise, it would start and run OK, but as soon as the boost gauge goes into the "boost zone" the power drops off, if I let up on the throttle, to get back into the no boost zone I actually pick up power. It will boost to 7psi, but the power is just not there. I drove it like this for two weeks, just being easy on the throttle so as to not get into the boost too much. I replaced my sparkplugs and did a compression test. The old plugs (Bosch Platnum...how old?) were covered in a white ash, with a black spot near the center conductor. New plugs changed nothing, same thing, no power under boost. I did a compression test. Cylinder #2 was low (80 psi), poured 2 tablespoons of oil into the cylinder and redid the test and still got 80 psi (my conclusion... bad valves in #2). But this did not explain why boost would go up and performance go down. I thought my catalytic converter could be clogged from the rich running and burning oil, so I cut it out and put in a straight pipe. This didn't help either.
Then this weekend just driving normal and thunk, the motor goes dead, tach drops to zero and just as quickly, starts back up again. It does this several times. If I keep my foot on the throttle and one on the brake, then I can keep if from stalling, sort-of. It did finally stall on me once, but then started right back when I put it in park and turned the key. It backfired once during this as well. I used a little deductive reasoning, and I figured that this problem is ignition related, (no tach and backfire, etc...) so I replaced the coil and the coil wire, the other spark plug wires are Volvo replacements that look to be in good shape. I drove to work 25 miles without stalling, but it did drop-off at idle a few times just to scare me. I may have band-aided the problem, but I don't think that I fixed it permanently.
Now, are the no power problem and the stalling problem related? I don't know. I am new to Volvo's but not new to cars in general. I do most of my own work, like all that I have mentioned above. I dont know where else to look. The stalling is an immediate problem that I cannot live with. The no power problem is something that I can deal with and fix later. I appreciate any suggestions that you could give.
Thanks,
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