Hi everyone,

Car background: 1993 940 turbo, 180,000 miles on original b230ft (squirter block), recently converted to M46 transmission (about 500 miles on the swap with the engine running normally, I've owned the car since 160,000 miles with no previous engine trouble)

Yesterday as I was driving home at about 35 mph I noticed my engine knocking/pinging under the slightest load - especially below 3000 rpm. Got home and the idle was rough. Any attempt to accelerate resulted in lots of very audible pinging/knock. However revving the engine under no load it sounded normal. So far, LH 2.4 has not thrown any check engine lights.

Further investigation seems to show that cylinders 1 and 2 are not firing at least at idle. Pulling the injector plug to those cylinders does not change the way the engine idles. 3 and 4 definately make a difference, pulling those makes it want to die.

Later I checked spark - 1 and 2 have spark and the plugs are dry. Also the timing for #1 is correct, around 14 deg BTDC. Timing belt has not slipped. I removed the fuel rail and cranked the engine. To my surprise, all 4 injectors fired.

I also checked the two ground wires at the fuel rail and they seemed ok. I'm a bit stumped by this - the only thing I can think of is that the headgasket could have blown out between 1&2, but I've never heard of this happening on a non hot-rodded volvo. Furthermore, there is no mixing of oil and coolant that I can tell, no excess smoke from the exhaust.

I plan to do a compression test this evening, but would appreciate any suggestions!

Thanks,
Eric