I took my truck out yesterday to help break in the new engine and all of the sudden it started acting out on me. I had a diablo handheld on it and my fuel trims on bank one were reading between 3, -3. But bank 2 was reading 50, 45. Can this be a bad oxygen sensor? What should I check? I took it slow on the way back home and I could hear knock at part throttle.

 

Doesn't sound like Bank 2's getting any fuel. start with your injector harness on that side.

 

I've had that happen a couple of times with HPT that it just didn't connect right for some reason. Cleared the LTFT, physically disconnected, then reconnected and they were reading correctly.

 

what do I disconnect? THe o2 sensors or what? I tried removing the battery in hope of clearing it but problem still there. I'll see whats going on after work.

 

mine read between + 13 and +16 at all times.

 

Ok, I changed the fuel filter, removed and blew off the o2 sensors and now fuel trims are even worse. Both short term trims are at 50 and both long term trims are at 25. Is this rich or lean? I'm thinking fuel pump or does it have to do with tuning?

 

Trouble shooting over the net is never easy. Is this a new engine/tune or is there somthing you have done recently, That may help someone diag this? But to go lean on one bank and the other soon after, I suspect some type of intake leak, exhaust leak, MAF, injectors some many things to look at? Wish I could be more help

 

It's a new 402 engine. I will just wait till I get a retune from nelson. I thought the truck should at least run with the old 5.3 tune though. The first night we started it up it was running good at part throttle but lean at WOT, then a day later it began acting up at idle, part throttle, and I don't want to go WOT like this.

 

Well there you go I would park that beast until you get her tuned. Custom parts custom problems if you know what I mean. Im just got done building a 408 myself and would expect nothing but problems from ad tuned 5.3 cal.. Its my first one so i'll keep an eye on this thread... Keep us updated