First off, i have a 1991 Z28 which has a 350 TPI. I recently got my engine rebuilt, and have been having the problem before i got the rebuild done. what initially happened, is one day when i was driving, the car became really sluggish, it wouldnt have any power, but i didnt get any check engine light. so, i thought it could be many number of things, including timing chain, distributor, and coil. so, i ended up getting my engine rebuilt, and has a new distributor (which means new EST), timing chain, coil, knock sensor, and other sensors. same problem when i fired up the motor, it would run fine for like 5 seconds, then the check engine light would come on, and it would run really sluggish as the computer trys to make adjustments to timing. ive looked into code 43, and it has to do with the knock sensor, and ecm with my car, i know on the 5.0's, theres a ESC, but mine doesnt have one. i have no idea where to go now, replace ecm? replace mem-cal chip? i know the computer probably isnt reading the knock sensor at all, because i unplugged the wire, and same exact thing happens, runs fine for 5 sec, then check engine light comes on. any ideas, let me know.

 

Hey I went through this same problem just this week and just now got the problem fixed a couple hundred dollars later. I had a friend change my tpi engine in my 1990 irock. When I drove it, it would run fine for a few then run sluggish and start pinging. Check engine light would come and go and read code 43. I dont have the ESC so I went to the knock sensor and replaced it. Still the same thing. A friend of mine runs a parts store so I tried a new computer and the same thing code 43. I went through and checked all my grounds and all looks good. Still had the same problem and the code 43. I took my car to a well known garage that I trusted and knew he was the best with the electronics. He traced everthing down and found that the knock sensor wire was switched with another plug in under the exhaust manifold on the right side of the car. He switched the plugins and low and behold no code 43 after he reset the computer and the car now runs great. I never would of thought about those 2 plug ins being crossed like that. So look at that and you never know could be it........