Won't Idle Correctly
 

I have a 1988 s10 blazer 4x4 with the 4.3 tbi that I can't get to idle/run correctly. When it idles, it sounds like it's underwater, or bogging down, and it shakes the whole car. Yesterday it was dying whenever I stopped, unless I gave it gas. When you give it gas, it runs a lot better, but still not like it should. So far I have tried replacing the distributor cap and rotor (which helped only slightly), the MAP sensor (did nothing, so I returned it) and I just replaced the IAC valve (which also did nothing). I am pulling codes 32, 33, 34, and 45, which is what lead me to the map and IAC. I am losing my sanity over what's wrong, and was wondering if any of you have had similar problems and what you did to fix them. Oh, and I just seafoamed my engine last weekend, which didn't help much. Any help would be greatly appreciated!!! Thanks in advance!

Knock sensor. EGR valve. Vacuum leak. Check for those.

I've already replaced the EGR valve because mine was absolutely filled with carbon, and I fixed the vacuum leak that I found. I sprayed carb cleaner around all my lines while it was running to find leaks and there was only the one. It still does the same thing, except it's gotten slightly better. What/where is the knock sensor?

They are usually in the side or back of the engine block. It looks almost exactly like an oil pressure sending unit. One wire clipped on the end or plugged into it. I don;t know exactly where there located on these engines.

Mine did the same thing but it's a 98. Idk if your has it but mine was the idle air control sensor. I didn't have heat or ac till I got it fixed. If you unplug your ac compressor and it runs fine then it's your idle air