I don't know what else to call it. I guess I originally heard it before the weekend, but it was so soft that I thought I was hearing things. I don't think it's an actual backfire--not loud at all--but more like a popping sound, a bit louder than popping a can of beer. It comes from the exhaust and only happened in the first 2 or 3 minutes after starting up the car. Nothing else seemed amiss, but I my drive to work is only 1.1. miles in the city, so it's not like there was time for any weird stuff to start up. Idle was fine. Maybe I'm paranoid, but I thought I'd post and see if any of you long-timers have seen experienced this.

might be the cat getting fuel on it and cracking when burned.. caused by rich mixture.

Happened to mine a few times.. made a "clink" sound.. more like ceramic breaking.. which is exactly what it is. My o2 sensor wasnt working and I had an extreamly rich mixture.. quit when I fixed the sensor.

I don't think thats the sound he's talking about. Lots of cars do it with no problems at all. It might be an exhaust leak in your case since it wasn't happening before.

I did some digging on roadfly and came across this post. I think it perfectly describes what is happening with my car.

http://forums.roadfly.com/forums/bmw/bmw-6-series-e24/4514819-1.html

Just thought I'd report back if anyone else is having a similar issue. I'll keep this thread posted if the situation worsens or clarifies.

I assumed you were talking about a repetitive popping while at idle or decelerating from high revs, both are common but not at all related to the roadfly discussion.

Sorry if I wasn't clear. It was just a quick "pop-pop" at low revs--I was at the crest of a hill about to head downhill (I live at the top of a very steep hill) when it happened. In fact, the first time I heard it last week was on a slightly less steep part of the hill, but also going downhill. Of course, being at the top of a hill, I'm almost always headed downhill when starting out.

Same thing happened to me going downhill on a steep freeway (24 between W.C. and the tunnel if you're from here) at 85~ mph, though it was more pronounced and produced some smoke.

just an idea, but as the weather has been warming my car warms up a bit differently, not quite as long an enriched circuit. You may just getting a leaner decel pop., probably nothing to worry about. If you have such a short drive to work, maybe the plugs are carboned up from winter short hop driving?

as the bmw manual states, after stints of city driving, you must drive the car above 3000rpm for at least 20 mins to "blow the carbon out". May also be a good time to get some injector cleaner, put some in with about a 1/4 tank left and run the snot out of the car for a bit, itll thank you for it...

-Jeff

as the bmw manual states, after stints of city driving, you must drive the car above 3000rpm for at least 20 mins to "blow the carbon out". May also be a good time to get some injector cleaner, put some in with about a 1/4 tank left and run the snot out of the car for a bit, itll thank you for it...

-Jeff

By injector cleaner do you mean stuff like Techron? If so, they already have it in Chevron gas and I only fill Chevron gas. Otherwise, can you suggest a brand? I'm almost down to a 1/4 tank.

just an idea, but as the weather has been warming my car warms up a bit differently, not quite as long an enriched circuit. You may just getting a leaner decel pop., probably nothing to worry about. If you have such a short drive to work, maybe the plugs are carboned up from winter short hop driving?

So it happened again this morning, as expected. It didn't happen yesterday evening on my drive home. The difference is that the M6 was parked in a garage all day. In SF, it's been a very cold couple of days since Friday and it rained last night as well. She was parked on the street the night before, so I'm wondering now if maybe the cold has something to do with it.

and maybe dampness too? how old are the wires?

I haven't changed out any wiring yet, so yeah, it's all pretty old.

personally I scrap wires at 20k miles or 1 year whichever comes first.

Joe, this is probably a very stupid question...but which wires are you referring to exactly?

the sparkplug wires. A lot of people say to ohm them for resistance but I don't buy it. 35K volt coils pretty much overide any resistance other than a break in the wire. For me, It's the outer and inner jacket that counts. Age, heat and minute perforations will let moisture in and voltage out hunting for ground. That's where a misfire can occur. I'm just suggesting this mind you. Your misfire could be just a gummed up ICV or some other simple bugaboo. Joe

I guarantee you wouldn't be changing M wires every year. What are they something like $300?