Hard jolts on acceleration from 45 to 60, Whats going on?

[DanH]

This has happened a few times, today it seemed worse. I was driving my 535iA to work this morning and started to accelerate slightly aggressively and the car shook hard two times during the acceleration like the engine died for a split second or the transmission was trying to lock up?

What could be the cause of this?

It was -9 F (-22C) this morning, I have only noticed it happen at temps less than 20F.

I just replaced the thermostat last Friday so now i have more heat! The one I took out looked like the original equipment...224k+ miles on one thermostat is quite amazing. It looked good, the spring was just weakened. So the engine had been running below normal temps for a couple weeks, if that is any clue.

Thanks for any input.

[callen]

I had problem like this on my 91 535i with about 200k and it turned out to be the ignition coil. Course I live in Texas and it wasn't temp. related. If all else fails try it.
Callen 91 535i 230K miles and running strong.

[DanH]

I am planning on changing my plugs as soon as i can find a warm garage since working in -9F weather doesnt allow much time before fingers assume a solid state.

I've had a set of Bosch plugs waiting to go in for quite some time.

If that doesnt help I'll do the coil/wires too.

Thanks...