CIS testing/trouble-shooting
 

Just rebuilt my 930. Runs great when I get it started.

I have a couple of strange issues. Car starts then I set AFR levels and as I mentioned it runs fabulous. Stop and go inside for a bit then come out, engine turns freely but won't fire. Checked spark and it is fine. Readjust the AFR to be rich and it fires up.

Car runs a little rough some back firing, obviosuly too rich, idle is low but adjusting idle screw seems to have no effect.

Timing is set at 29 BTDC at 4000RPM.

Is this a typical CIS issue? I never had an issue starting this car before the rebuild. In fact it fired up quicker than my buddy's 97 Viper.

This car always did run rich especially at start up, before the rebuild.

Any tips on what to check or how to debunk? CIS issue?

Thanks

If you have a warm start issue, the first thing to check is residual fuel pressure.

If it runs rough and backfires it is probably too lean. You usually don't get backfires with rich mixstures.

Sounds to me like a vacuum leak somewhere in the system.

Check all your hoses, fittings and manifold boots for leakage.

I haven't had a chance to really look at mine, but my 83 930 runs a bit funny as well. I'm thinking it is a vacuum leak somewhere.......

Mine starts and runs fine when warmed up, but upon first start (cold), it bogs with very little throttle input and feels a bit anemic.

It runs this way until it gets a single backfire (more of a pop), from that point on, it runs well.

Great throttle response, great power, and no hint of being anemic.



Again, I think mine must be some sort of vacuum leak, but why would a single pop or backfire make it run better?

My '83 SC CIS did exactly that until I fixed the leaks.