OK, first: I've scoured the threads and have found others with similar problems, some explained better than others, but none with my simple yet confounding symptoms.
I bought the Blazer new. Traded my 91 Cavalier which I bought new. Am en engineer and have never had my vehicles in the shop (except for warranty work) - I've done it all. I'm the poster boy for Blazer TSBs - suffered through nearly all of them. DexCool is evil.
OK, got sidetracked. I'm worried I'm going to have to have the Blazer towed to the dealer for repair. The thought is worse than emasculation...
So - DTC P0340 set twice. This has been a recent, intermittent issue. No other codes. Always after air period of driving at temperature. Tech would jump wildly, peg-out high, and after a brief period of rough, crappy performance would settle at 0rpm and driving would be normal but lacking power.
Replaced the cmp sensor. Truck wouldn't start - just cranked and would cough a couple times when the key was released to run.
Put the old sensor back in. Same thing.
Replaced the entire distributor, cap, and rotor. No start.
Tested the supply, ground, and signal at the cmp all is fine. Working out of the 3-volume service manual set for my truck.
I'm at a total loss. What should've been a quick sensor replacement is about to become 3-day ordeal. I've worked through the "cranks but won't start" section of the manual and that posted here- but to no avail.
It simply can't be so complicated...
Thanks for any thoughts!!

 

Wish I could delete this double-post...

 

Anyone anywhere?
I've seen this condition mentioned many times but the follow-up wasn't enough to use for a conclusion.
The high-stakes is as if the timing is way off. This can't be -at least initially- since nothing was changed to affect the same. The rotor and cap we're replaced correctly (triple-checked).
There is no relearn for the cmp; in fact I've seen that the cmp doesn't affect drivability (not so sure about this).
How could simple R/R of the cmp with no other changed cause the no-start?
When I **** it off it was running poorly, tech going crazy, but no SES just yet it was about to set.
I wonder if I **** down when it was in some intermediate diagnostic state and some stored information was scrambled?
Thanks.