A few weeks ago when I changed the fuel pressure regulator. I noticed that there was a lot of carbon deposits inside the plenum. I took the EGR valve off and cleaned the EGR valve and port of the carbon build up. Yesterday I removed the actuator above the air intake port (see picture) and the spring and piston was completely encrusted with carbon to the point that there was no way the piston could move. I cleaned it with carburetor cleaner and a small screwdriver and after I put it back together and started the Blazer it was quieter and has an even smoother idle. It only took about 20 minutes to do and I think this is a worthwhile PM for all owners. You need a T15 torx to get the 2 screws out and there is an O ring that you have to be careful not to lose.

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That's not the EGR valve, but it can get carbon'd up pretty good too. That is the IAC (Idle Air Control) valve. Only word of caution would be to not move the pintle on the valve itself while cleaning it.

 

Thanks for the reply. Yes, I knew that that part is not the EGR valve. The EGR valve was well exposed when the top of the plenum was off and made it easy to remove and clean the port. I did not know that the IAC was the name of the part I cleaned yesterday but I will bet that the IAC valve will make many people on here happier if they clean theirs too. Seems that many have been unhappy with how their Blazers are idling and I have not seen one mention of that valve until now. If it is the Idle Air Control valve it only makes sense that it would affect how your Blazer idles if it is all carboned up and sticking as mine must have been. I only wish I had cleaned it before I changed my fuel pressure regulator because I have a feeling that there was nothing wrong with my spider injector assembly to begin with as I was informed by my mechanic. Especially since it is now running as well if not better as it did before it began to run rough and was diagnosed as being the problem ($500 spider injector assembly) and I have not replaced my whole spider injector assembly. Thank God.

 

I lost my 0-ring for my IAC the other day while I was working on it....cau I get a replacement, or do I have to guy the entire IAC assembly?? I also moved the IAC Valve up and down so that I could clean the shaft off, did that hurt my IAC Valve? Right after I cleaned it it idled smoother that it ever had, then I pulled the plenum and removed all of the carbon, replaced the FPR and buttoned everything back up, and it ran awsome for a bit, but now the stumble is back....could I have gotten bits of carbon in my EGR and IAC Valves? I had quite the carbon buildup around my EGR Passage, on the lower and upper plenum, as well as everywhere else...even after 2 seafoam treatments it was very black...I sprayed the upper plenum down with carb and choke cleaner and let it sit while I was fiddling with the FPR, then drained it out and wiped the entire thing out....now it is clean, and it starts and idles alright when it is cold, (before it would stumble and miss if you started it cold) and now it idles rough when the engine is warmed up....Im confused, I will probably pull the EGR and IAC back off and clean then once again...then do the plugs again, cause of the NGK's that are in there...I bought new Autolite Platnums to replace the new NGK's that I have in there...don't like them! Anyways, any words of advice would be appreciated.
Ryan

 

I found my O-ring, it was still sitting on the top of the radiator support....removed the IAC and it was carboned up again, so I sprayed it down again, and reinstalled it with the O-ring, but the idling is still the same, it is like the IAC is moving in and out, so it revs up then drops, revs up then drops over and over again....still not sure what the problem is......please someone help me!! it is s 1994 S-10 Blazer with the CPI Vortec....I've replaced the cap and rotor, plugs and wires, FPR and associated gaskets etc.., and cleaned the IAC....I may pull the EGR back off and clean it again, but I just don't know. Im about to give up and take it to a dealer, im tired of this hit and miss process.....I may just change the plugs out and install the autolites, to see if that helps a little bit or not, but I really don't want to do it again, it was a real PITA.... I need some help please!!!

 

It's because teh EGR gets dirty again. You can replace the standard EGR gasket with a netted one designed to stop this problem. Just ask about it advance, autozone, etc.