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Solve this strange engine problem

vehicle: 1987 BMW 325i with 6-cyl M50 engine, circa 200,000 miles

I idled it for about 3 hours and when I started to drive, I noticed really poor performance, the engine would choke, lack power, like it was dying and lost all compression. The really scary thing was, lots of smoke from the exhaust pipe, so bad I could see it from the rear-view mirror. This engine never smoked.

I pulled over, inspected the vehicle and added about 1/4 to 1/3 qt of oil. After that, the problem went away, the smoke, and really bad hesitation. All is back to normal.

Can someone explain this? I thought my engine was gone for sure. I don't understand why adding oil fixed it as I didn't even add very much. And even if that was the problem, how could low oil cause hesitation or smoke from the exhaust? ( I only saw it in the rear view mirrow, so I couldn't determine the color, but I think it was blue )

BTW, The oil disappears from this thing at a rate of about 1/2qt per week, or per 400 miles. I think it's leaking.

Reply to
SQ
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My guess is the valves got loaded up with carbon. that can happen if the idle mixture is too rich. Running it at higher speeds blows it out.

Reply to
Ed

I would bet it's burning it. The signs you saw are classic for bad valve stem seals and worn rings. Bet the valves are carboned up really good and soaked up a bunch of oil. When you hit the gas that oil was drawn into the engine and caused your problem because oil doesn't produce much power compared to gasoline and the smoke is due to the excess oil in the cylinder.

Time for a $$ rebuild $$

Reply to
Steve W.

For THREE HOURS?!? IF that's not a typo, then that's the problem. The thing loaded to the gills with carbon. Adding oil didn't do anything at all, just driving it cleared out enough buildup to let it run normally. That probably wasn't "smoke" you were seeing, but carbon grit blowing out.

Why on earth would you let a gasoline engine idle for three hours? That's extremely hard on them.

If its leaking that much, the underside would be slicked down pretty good. My guess is that its burning it, and the oil is largely responsible for the carbon buildup when idling, and also may have coated down the insides of the exhaust plumbing so that it contributed to the smoking when you drove it and burned it off.

Reply to
Steve

I'll bet he started the car using his remote starter, then forgot about it.

Reply to
Hugo Schmeisser

STUCK CHOKE, MAYBE.

mho v=83e

Reply to
fiveiron

Steve,

Thanks for explaining it, that sounds right on the money. I wonder if the worn rings and bad valve stem seals contribute to terrible MPG I am getting. Poor compression maybe?

I know it's leaking a bit of oil but I suppose it's burning most of it.

Reply to
SQ

overhaul it man ring oil pump rod n main bearings .. itll probably another 200,00 after that..

Reply to
pigcharger

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