90 Blazer S10 won't stay running

I've got a 90 S10 Blazer that will start run for 5 to 10 seconds and die. It will finally start and stay running as long as I don't shut it off, if I do everything starts all over and it can take 5 to 10 tries to
get it going. So far I've changed , cap, rotor, plugs, fuel pump, ignition modular, fuel reg, and the map sensor, anyone else have this problem and what was the cure? TIA
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EGR valve or clogged cat converter ..EGR clogged w/ carbon will cause loss of idle; will die at stop lights etc unless you keep high idle with accelerator. Clogged cat causes severe loss of power /dying.

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No that's not it, when it does start after 6 or seven tries it will run fine.
Curmudgeon wrote:

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so if you know what the solution is, why not tell us?

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If I knew the solution i wouldn't be asking the question, I'm just telling you what I've tried and that it still has a problem
burntkat IS AT sc.rr.com wrote:

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It can be one of several things:\
But, here are the things I would first look for: An exhaust leak before the O2 Sensor, as in the donut gaskets and the manifolds to the block!
Check for donut gaskets, and even at the Cat to cross pipe connection. This causes a vortec and actually vacums in excess atmospheric air.
Secondly, get an exhaust back pressure checking fixture, check the back pressure at the O2 bung. I have an old Thexton that pierces a hole, the nipple is a 1/4'x20 thread tap and nipple, I use stainless bolts to block off the holes. If there is 2 pounds before the converter, it is suspect, 3 pounds and it is a piece for the core collectors.
Also, have you checked spark intensity with a cheap adjustable spark tester? It should jump 3/4's of an inch without a problem, any less is a problem. maybe a weak coil?
These are seat of the pants guesses, and I can't help unless you do these basics and post back. Please feel free to ping me for any assistance and no wise ass attitude!
Refinish King
PS Doc, Charles Bendig and my self are always nice guys, trans Surgeon was a nice guy, but unfortunately he got sick of the internet anal fistulas!

to
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Well after changing everything a friend suggested I try the ignition switch, problem fixed (so far)
Refinish King wrote:

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