Can't really help you on the cat conv, I've never owned a vehicle that had a problem with that. I am having issues with the emissions (I think) on a '91 S-10 Blazer 4.2L so I'm watching threads on EGRs and such. As far as a computer needing time to re-adjust I believe it's true. I once was extremly late on a tune up and after performing one on it the truck ran like a bat out of hell but the valves were pinging a little. My machanic said the computer needed some time to adjust to the newly installed parts. Vehicle computers are capable of "learning" conditions and adjusting to what will make the engine run at top performance, i.e. altitude when driving in the mountians, among many others. Don't know if pertains to your situation though. Good luck with it.

 

https://blazerforum.com/forum/1st-generation-s-series-1983-1994-tech-40/93-vacuum-loss-rough-idle-40673/
If you look at this post it's the checkout for the EGR Code 32 from the factory manual (written in 1992) for a Vortec. It's everything there is. Most of it you can do without a Tech 1 scan tool. If you need some interpretation post again. yes. EGR is code 32.

 

I believe the problem has been solved. I found out the code 32 could be an EGR valve or EGR temp sensor. Replaced the temp sensor still ran terrible. I took the top end of the motor off and found a blown lower intake gasket, and a ton of hardened carbon. Replaced the gaskets and it ran fine until chunks of loosened carbon started clogging my EGR. I probably took it off 5 times today to find it stuck open. Replaced the gasket for one with a screen and it seems to be working. Thanks for all the advise.

 

Cool. I just love it when someone at ;east tells us it's fixed.

 

but i hate it when someone tells me its the intake manifold gasket since i just did my intake gasket about a month ago cause i had water in my oil!!!! my problems are exact same, i just dont have a cat, mines a 95 with the 4.3L Vortec, but the surging problem is exactly the same! i'm running mine on the scanner tomorrow, i know it'll throw the O2 sensor, i guess we'll have to see what else. Better not be the intake gasket though!!

 

make sure when you replace your intake gasket, that you use a LOT of sealant around the front and rear (water) openings on both sides, otherwise you'll do like I did, and replace it three times with a nice thin layer of sealant, which allows it to leak anyway, even when torqued down properly, creating SEVERAL needless oil changes, radiator fluid changes, and busted up knuckles and curse words. Put on a nice THICK layer of sealant on the intake gaskets at each end, and be CAREFUL to drop it down straight and NOT move it AT ALL when tightening the bolts. Then you "should" be ok with the water in the oil problem.

hope that helps

chris

 

It should be said that to use sealant around the water ports on the newer engines (96+) may actually cause a leak. The older engines with fiber gaskets, have at it, but with the newer o-ring style gaskets, you can cause more problems than you solve by slathering on the silicone.

 

yes indeed, the silicone can overheat, meltdown, come loose, and really gunk things up on the 96 and newer, however with the gaps on the 95 and older, permatec can be your best friend