91nb

Hello everyone,
bought my 2002 C32 in june 2016, it had 110 000 miles on it and was my pride and joy for 60 000 miles of spirited driving.
April 2019, after a 60 mile fast autobahn journey, fairly pushing the car. It started misfiring on cylinder 3, misfire would disappear upon restarting the car.
The following day I wanted to drive it 20 miles to the shop, and boy did things go south quickly.
Cylinder 3 started misfiring again after 2 miles, then while I was looking for a safe place to stop, within half a mile cylinders 2, 4, 5 and 6 started misfiring as well (OBD reader was plugged while driving), followed by a rather strong explosive sound, a cloud of blue smoke, and engine shut off.

Trying to restart the engine resulted in very loud knocking noise.

Left the car at a friend's shop and it has been sitting there for almost a year, he's been very busy and so have I.

He will soon be taking the engine out, and checking under the valve covers, doing compression testing etc. Given the noise I think there are some broken internals and the 2 possible choices are scrapping the car or buying a second hand engine.

Will keep you updated on whatever comes up, if any of you are interested.

Has anyone had a similar quick misfire to total failure transition?

Oshkoshbigjosh

Would be a shame to scrap it. Less and less 32’s on the streets as time goes on. If you can go through the trouble of dropping in a new engine then it would be worth it and you can sell and recoup some loss or at least drop in the engine and drive it again. What could have caused the engine to blow?

91nb

It would indeed be a shame but here in France it is very hard to find a second hand M112K, there is only one on sale in the country and it's a 2002, so basically exposed to the cam problem.

I think I will give it a try anyway. Money is not really the issue, as I do not intend to sell this car if I repair it, but rather continue using it on the weekend, especially since it is in very good condition: body and paint are immaculate, it had a suspension overhaul in december 2019, a new air conditionning compressor mid 2019, a new alternator in 2019, a new crankshaft pulley and tensioner pulley in 2019.

Given the sequence, I think there are 3 main hypothesis:
-Either it has been leaking from the intercooler for a while and it ended up causing the misfires (especially since the car had been needing coolant top off for 15 000 miles), but this doesn't explain the exploding sound and the loud knocking
-Or there is a clogged cat issue especially since the exhaust had been rattling a bit for a while, with backpressures so great that ignition got compromised
-Or it is a 2002 cams issue

This is still all pure speculation and we will know more as soon as the engine is out of the car. Do you have any other ideas?

I hope to know more soon.