KOOL!!! Thanx Doc...It never dawned on me to do a vacuum test on the engine
to test for low exhaust flow!
That's why your the 'Doc'!
| > So I'm replacing everything from the cat. back, but I'm curious about the
| > converter itself now. How do you tell if it needs replaced? The truck has
| > 208K on it, but I don't ever detect any rotten egg smell, etc. The outside
| > condition of the converter is good, but I'm sure it is original.
| > Thanks,
| > John Manner
| > 4.3L 4x4
| > 1989 S10 Blazer
| With the engine hot, at idle, in park, hook up a vacuum gauge to one of the
| TB vacuum ports. Should have between 17-22in/hg. Tweak the throttle a few
| times. Vacuum should drop 2in/hg then pop right back to where it was at
| idle. Next, hold the throttle at 2k rpm for 5 seconds, then 3k rpm for 5
| seconds. Vacuum shouldn't budge more than 2in/hg from the idle marker. If
| it doesm this indicates resistance/backpressure in exhaust and likely a
| plugged cat.