Ok guys, I just bought a 1991 2 door blazer, 2wd with the 4.3 v6 and the guy that I bought it from didnt know what was wrong with it, it idles rough and shakes when its in gear but stationary, when I take it out of gear it idles fine. I dont know what the deal is, I havent messed with too much on fuel injected motors with all the extra crap on them like o2 sensors and what not. I was thinking it might be the o2 sensor, but just wanted to check and see if anyone might have some insight on this.

Thanks,
Nathan

 

check the IAC valve. With the tbi motor it will be on the pass. side of the throttle body. with the square plug.

 

Thanks, I replaced that tha yesterday and it continued, so today I removed my cat and put a new o2 sensoer on and that helped a little, the reason my old o2 sensor wasnt working was because the wire was rubbing on the exhaust and it burnt. Then I spent a couple hours online looking for vacuum hose diagrams and found one and discovered that someone hooked the lines up all wrong so i fixed that but it still idles kinda rough, so im not sure what to do now, but now that my vacuum lines are all correct my check engine light is not coming on!!! I dont know what to try now!

 

If your old O2 sensor wasn't working, you might have been running rich for a while. So check the usual places - throttle plate, EGR valve, etc for carbon. Oh, and check the PCV valve for proper operation, too.

 

Ok thanks, I changed the pcv valve this morning and ill try and tackle the rest of that stuff this weekend. I hope that gets it running smoothly again, it only has 135,000 miles on it, it still has alot of life left, it runs really well, minus the idling but ill try to get it fixed soon.

Thanks