running issue
 

So I'm having some issues with my '82 930. Originally I had the bouncing tach issue, so I had the alternator rebuilt and put in a new battery (the battery needed replaced a while ago). I also checked and cleaned grounds. That seemed to be an improvement; however, now the issue is a jumping idle, it'll drop about 200 rpm then jump 400 rpm. When it jumps the engine seems to sound labored. While driving the AFR is richer somewhere between .5-.75 richer. Fuel pumps are about 3 years old; Leask WUR, MSD CDI & coil, plug wires, rebuilt distributor are about 10 years old. I think the spark plugs are 5 years old.
I put about 2-3,000 miles a year on the car (short summers here in Montana)

Any ideas before I get into trouble shooting? I'll start checking the normal stuff but thought I'd check with the group to see if anyone has experienced something like this before.
Thanks, Frank

Hi Frank, I would check the coil next, then report back.

Best of luck,

Rahl

So it took a little while to check things out. Here's what I've done. Checked coil and it checked out good. I checked out the ignition system, the rotor and cap looked good. I changed spark plugs from Bosch to Denso Iridium IW24 (based on recommendations on the board). It seems to have solved the issue based on a quick test drive to town and back; however, I now seem to be running rich by about a full point. Would new plugs cause the AFR to read rich? My ability to trouble shoot then drive is coming to an end for the season here in Montana. The last time the car seemed to start running rich I had a fuel pump failure.
Thoughts?

That sounds like a generaly rich engine. The WUR pressures should be checked. And the idle mix.
Alan