1995 4.3 CPI Misfire When Warm

Well being new to AF I will start my first post with a good one. For my winter project this year I picked a 1995 Blazer with a blown engine. I completely overhauled the engine . It started right up and seemed fine. The problem is after the engine warms, it runs rough at idle up through part throttle. After 1/3 or more of throttle it will smooth out wether your in park or driving down the road. I don't know if it did this before the engine failed or if it is a new problem as I only started it long enough to know the engine would turnover before I bought it. Any way I checked the TPS and the res. of the IAC and they seem fine. I am suspecting a vacuume problem or the EGR because it runs fine untill is starts to warm up and after part throttle . I have to run to get a new gauge to test the vacuume and the EGR I will have to guess. I don't know if the CPI will cause this or not. Any help or ideas would be appreciated . I am just learing about the CPI . Also in the rebuild kit there were six O rings. Were these for the poppet valves or for the 96 + engines. when I removed the poppets there were no O-rings. Thanks

Check the egr valve real close.
Remove and check for carbon build up or carbon ball under plunger.
How is the base timing and fuel pressure?
Got any codes or check engine lights?

Thanks for the reply, I took off the EGR, it was alittle sticky . I will clean it up tomorrow with some carb or contact cleaner. It dos'nt look all that bad though. Am I able to check the base timing on the crab style cap ? I did'nt even look for the bypass wire because of the dist. being pinned . I have the upper manifold off now making sure the CPI was'nt leaking. I could'nt find any leaks( of course). When I get it back together I was planning to test the compression , Fuel pressure, timming if possible, maybe the EGR will help. No codes or lights - I wish

On the newer style the timing is not adjustable.
However you need to get it on a good engine capable scanner and check the camshaft retard setting.
Which is about the same as setting the time.
Done by rotating the dist.
But it does not change the timing but centers the dist rotor to fire dead center on plug with terminal in cap.
Good luck MT.
Set camshaft retard as close to - or + 0 degrees as you can.

Well, I found it. GM's great Linear EGR valve. I was'nt going to spend 174.00 to 'TRY' a new one so I figured I would try to clean my old one first.It must have been moving enough not to set a code. When I took it off it did'nt look that dirty but the valve felt 'sticky'. I took a small screwdriver and carefuly scraped the carbon away from the valve and seat area. Then I cleaned it with Electrosol 140 contact cleaner. It still felt sticky so I took alittle valve lapping compound and lapped it in using the torx bit hole in the top of the valve and then used the contact cleaner again. I dabbed some high temp anti-seize( a very little bit just enough to put on the thinnest coating) and put the unit back on. It worked great and ran smooth. I have put almost 200 mi. on it in the last couple of days and no problems. Of course I don't expect it to last long, but I will feel better about spending the money when it does happen again. If anybody tries this, it is at your own risk. I figured I would have to replace mine anyway.
MT-2500 Thanks for the reply's

You are welcome.
And thanks for posting back the fix and how it went.
Glad all worked out and went well.
MT