Lumpy idle?

[canada karl]

Is this normal for our cars? Anyone have a video with sound of an idling E12? I have an 85 cyl head on my 76 530i but that wouldn't make much difference would it?

[franky2fingaz]

Can you elaborate more:
1. Lumpy meaning almost stalling out or shaky?
2. Idle at starting cold vs. warmed up?
3. you Just bought it, head was recently done or while back?
4. When revved it smooths out or remains shaky?

so many possibilities between ignition, fuel, timing etc.. If the head is an 85 for sure meaning B34, on a B30 there's a change in compression ratio, but not 100% sure . ...

[canada karl]

Sometimes when you change a stock cam for one with a different profile for performance you'll notice that the the motor will idle somewhat irregular and the idle speed will have to be increased to get a steadier idle.I suppose the timing could be off a bit and that's the first thing I should check. I thought I had read on this forum that the E12's sort of idled unevenly instead of smoothly and that's just the way they were?

[Mike W.]

The head would be the same, at least as far as valves, combustion chamber and anything else that would affect idle. M30s aren't known for a silky smooth idle, but you know that. Check basic tune up parts, check for vacuum leaks and consider adjusting the AFM bypass.

[canada karl]

There are 2 small vacuum outlet pipes on the motor close to the firewall that are plugged with those rubber stoppers. One was missing and the other ready to fall off. Replaced them and the Big Six sounds pretty good now.

[RonDwyer]

I solved mine by taking my 30 inch screwdriver and using it as a stethescope I put it on each injector and listened to the handle stuck in my ear. I found an injector not mated to its plug.

Vacuum leaks? Are your rubber lines all NEW or hard as fossils?

Work backwards, eliminate the known culprits.

Also, is the valve cover tight?
Is the oil cap secure? These leaks let air directly to the intake through the crankcase. I don't recommend flooding the crankcase with propane as i have heard before.

[CBradio]

when you pump the brakes when the car just starts up, do the RPMs go up?

how about at warmup? do the RPMS go up, or down???

Maybe its a mixture issue, which could be because of a vacuum leak...