[s-cars] Occasional stumble......

[Jim Fleischer]

Hey guys,

I know this is a pretty common discussion, but I'd like to see if there are other possibilities other than the typical vacuum leak, coil or POS failures.  I have a stumble that has been getting progressively worse, now occurring at lower throttle than WOT.  On occasion, during a stumble the CEL would illuminate shortly, then go out.  Under one circumstance, a WOT pass resulted in severe stumble, CEL lit, and reduced power to a stall (Limp mode?)  Restarted a minute later to "normal" operation.  I've retorqued the spark plugs (#1 and #2 were not "loose," but not tight either,) inspected normal areas for vacuum leaks and re-seated the fuel injector connects.  Upon reading recent posts about O2 sensors, I realized I haven't changed mine in the time I've owned it (5 years and 80K) actually have not had to do much in the way of sensors (CPS 2x, that's it.)  Plugs and boots have 7-8K miles on them.

So, besides the inevitable coil discussion, any thoughts on starting with O2 and other known sensor failures at the 130K mile range to weed out the possibilities?

Also, is there any way to test a coil to see if it is working properly at load?  There is no problem at idle or slower speeds.

One more thing, what diameter pvc tubing do I need to fashion a proper vacuum pressure tester for the AAN?  The one I made for the urq doesn't fit.

Thanks all.....

Jim Fleischer
'95 urS6 avant with 130K