For a while my wagon spewed oily soot from the exhaust. The engine died before I had a chance to figure out what was up with that (maybe it was a symptom). It got pretty nasty near the end there.

The car sat for a year, and now I've put a new engine in it. No more crap coming out the exhaust! But...

When I drive the car, I get no smoke (at idle or during acceleration) whatsoever when it's cold. Even when it gets to operating temperature, it's initially smoke-free. Once I've gotten past the ten or twenty minute mark (depending on city or highway driving) however, it'll start gushing clouds of light grey smoke at idle (I think it's there when I'm moving, too, but it gets pretty spread out so it's harder to notice).

And when I say gushing, I mean it. When I make my first stop after coming off the freeway, I see it literally billowing out the back, or, if the breeze is in the right direction, wafting along out in front of me. People in the crosswalk fall to the ground, gasping for air, flailing around like fish out of water.

Okay, I might have made the last part up, but I do get lots of angry looks .

It varies depending on how long the run is; if I'm on the freeway for 40 minutes or more, my car sometimes virtually disappears in the cloud it creates! (On the other hand, it makes it harder for the surviving witnesses to pinpoint me as the source of the mass pedestrian fumigation.)



My best guess is that my resonator and/or muffler has built up a huge stash of oily soot, which begins to burn off only after the exhaust system warms up enough.

Does this sound reasonable to anyone else? Would grey be the correct color smoke for that sort of thing? Could anything else cause this weird behavior?

I've also had power issues with this new engine. I've assumed it was related to the strange timing issue it's got, but now I'm beginning to wonder if it could be a symptom of a restricted exhaust.

What's the best way to confirm this short of breaking out a saw and hacking off the offending bits?

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)