Revitilization of a old C230 continues - very rough idle when in drive - ideas?

[Doug427]

So, now that I have the key issue resolved, it's on to the next two problems, a rough idle when in drive, and a inoperative air conditioning. I'll start another thread on the A/C issue, for now here's whats up with the engine.

It runs GREAT. Lots of power, drives smooth, etc. The only problem is that in neutral and at idle, it's a bit of a rough idle, and when I put it into drive at idle it gets significantly worse. I suspect that it gets worse because when dropped into drive the RPM's naturally drop, making the problem more exaggerated. There is no check engine light on.

I have cleaned both the throttle body and the mass airflow sensor with the appropriate cleaners. Those both made little difference. I have looked for vacuum leaks and don't see any. What's the best way to do a very thorough sweep for possible vacuum leaks that I may be missing?

Is this a known issue? Any suggestions on where to start? I hate to just start throwing parts at it without any direction.

[John Jones Jr.]

I won't suggest you throw parts at it like coils, plug leads, MAF etc. Get it checked on STAR is my advice and go from there. Or if you're feeling lucky buy one coil and see if that solves the problem.

[Mike51809]

I'd look at motor mounts.

[John Jones Jr.]

If the mounts are that bad check for damage to the front exhaust hanger and intercooler mounts.

[js81]

I'd look at motor mounts.

^^Agreed. Though mine wasn't nearly as bad as what you describe, once I replaced my mounts mine idles smooth as silk (in drive, AC on).

[Chisel86]

I too will say motor mounts need replacing. And it's easy to check the spark plugs and replace if worn.

[Doug427]

Engine mounts on order. I'll let you guys know how it goes.