I've been troubleshooting a friends truck. We completely rebuilt the top half of the engine. Rebuilt heads, new cam, new timing chain, lifters, etc. It still has an issue with timing. We tried a new and swapped back to the old tps, map, iac sensors. The new ones didn't make a difference. I also tested the old one and tried a new icu under the dist. No help. It wasn't throwing any codes, but it would not run good when set at 0 deg. timing. It would stall and backfire. Bump the timing up to 4 or 6 deg. and it runs better, but still will backfire and fall on its face when you put your foot into it a bit. So I changed the knock sensor, connector, and ran a new wire most of the way up the harness. NOW it throws a code 43! I tried another new knock sensor, and still throws a code. If you unhook the battery, and let it sit a bit, it will run for a bit when you first hook it back up, then throw a check engine light, which will stay lit from then on. (only way to get it to stay off a bit is to unhook battery). Then it slowly starts running worse. I had the timing back down to 2 deg., and now just bumped it up to about 6 (this is with the icu plug unhooked), and it seems to run the same, maybe worse.
I also just tried a new computer tonight, no luck! Help! Doc??!!