91' 350 miss at idle

[arkhogs2011]

Been chasing this down for years honestly but never drove the truck much until now. Its a 91 tbi always ran rough finally the TPS sensor went out recently so I replaced it also the IAC and the map thought for sure it would clear it up. It didn't finally got an EGR code the valve was not working replaced it and tested the solenoid which is working and a few broken hoses. It had a tune up late last year cap, rotor and wires. pulled the plugs out yesterday which were way out of gap fixed that. Also checked for vacuum leaks with break clean. All my codes were gone but still with a rough idle though I would give it some drive time and about 30 minutes into it got a ESC code, code 43. I did also timing back to zero. Truck runs great down the road and pulls two RZRs and a 21 foot trailer great. It will idle around 900-1100 but drops way low when in gear and sitting still. Any ideas would be appreciated guys. Thanks

[SnakeEyeSS]

You have covered about everything, have you tried new plugs? Maybe there is a break in them you can't see. Not real common but who knows. Check every connection on the vacuum lines also, even if the line is good maybe a clamp is loose or something. Oh and your gas cap seal. I don't remember a loose cap ever causing mine to run rough but it's been a while, and if it's more of a stumble than a miss. 

 

I think a code 43 can be caused by a knock sensor also, make sure it's plugged in and has a good seal.

Edited May 12, 2018 by SnakeEyeSS

[Logan Lanfear]

How did the plugs look other than being out of gap?  Just because they're new doesn't always mean theyre working right. Start by testing for spark on each .  

[arkhogs2011]

The plugs were not awful but I did replace them which also helped that much more. Every little thing it seems to help. I will check the knock sensor. I did a compression test which was all over the board so I’m going to see how out of wack the valves are today.