Ok, storytime. This is the biggest pain ive ever gone through on a vehicle. So a few months ago I bought a 1992 Camaro RS 305 TBI. The guy said it needed an IAC valve. So, as im driving it home, i see the check engine light come on and it starts idling like crap so im like ok well he said it needs an IAC.. Since then everytime I drive it after a certain amount of time the check engine light comes on and it does that thing. I get home and the next day buy an IAC valve. Same problem. Did new battery posts because the old ones are stripped, new coolant temp sensor (not sender), checked vacuum lines, checked fuses, then I checked for codes and it read 25 which is the manifold air temp sensor, replaced that, reset the ecm, test drove it and it did the exact same thing. I get back and decide to check for shorts. I found that one of the wires was exposed and touching the other one. I put shrink wrap on them and reset the ecm knowing this had to be the problem. I fired it up just for it to idle like crap for a few seconds and die.. I fired it up a few more times and it did the same thing.. I finally fired it up, hurried and put it in drive while giving it some gas and it went.. seemed to do fine while driving down the driveway, then I parked it and came inside to write this post while being VERY VERY frustrated. Any help is greatly needed, thank you

 

 

 

Grounding can cause many of these issues...and many people overlook the woven ground cable that goes from the passenger side head to the firewall...many people forget to reinstall them, which means the ground is through the engine mounts. When the engine mounts shift under load, you lose the ground.

Can't say for sure that's your problem, but over the years, I've had two older cars I bought that had this exact problem. Definitely worth checking out.