This surging, hesitation, thing is driving me absolutely insane. It only happens at WOT, if I'm at 3/4 throttle and in boost, it's fine. Driving normally is fine too. The issue started happening about a month ago, then I lost 2nd gear on the 4L80E. I just got the truck back with a new built 4L80E, thinking the surging/hesitation would have been attributed to the transmission, but it's doing the exact same thing! Tomorrow I'll be changing the plugs/wires but I'm not getting any CEL's and no knock (according to the aeroforce gauge) when the problem happens.

Could it be the torque converter? I don't think it's the tune as it's Kyle's old truck and the thing has been painstakingly tuned by him before I bought, and I haven't made any additional modifications.

https://www.dropbox.com/s/tshtktgqfy...503_003132.mp4

https://www.dropbox.com/s/s4z6e1rr6v...503_004010.mp4

Any help would be appreciated.

 

Are you logging data? It looks like your AFR is bouncing around quite a bit under WOT. I think I saw it hit 13.6. Be very careful, 13.6 under boost (hell even in a NA engine) can ruin it quickly. I would log it so you can see what your AFR, and timing are doing.

 

Thanks for the response Gadgetized. Unfortunately I don't own HPT or EFI Live (which it was tuned with). Yesterday I took it to a reputable tuner in Houston to see if he could datalog it, but the tune was locked. We put it on the dyno and he logged what he could while doing a few pulls. Ironically, the symptoms weren't able to be replicated. It was incredibly frustrating. The truck pulled smooth and hard, the tuner said from what he could see it looked solid.

Skip a few hours to last night, I got on it and low and behold it started acting up again. I do see the AFR being squirrely when it happens, so I don't know what to do. I'll have to wait until Kyle is back up and running and see if he can datalog it on the street.

 

Fill your fuel tank to the top.

It should be good at over 1/2 tank, but would eliminate that variable. The pump might not be sitting exactly on the bottom of the tank. That is something that would not show up on a dyno like in real world conditions.

 

Unfortunately I had a full tank last night. Ironically though, I'm sitting in my truck right now and looking at the gauge and it's bouncing between full and 3/4 full like crazy.

 

When you filled it up last night, did the fuel pump handle click off or did you go by the gauge? If it was truly filled up it almost sounds like a bad connection in or at your fuel tank. Do you have the ability to watch fuel pressure with a gauge?

 

i have a similar problem and i think it is caused by belt slip at WOT.. i can't prove it but it makes sense.. going in and out of boost is gonna change your AFR and the way your trans reacts.

 

Yeah I let the handle click off. I'll have to find a way to monitor the fuel pressure. Yesterday the AC belt came off the pulley so I had the truck on jack stands. Interestingly enough, when I was done and took it for a stroll to make sure the problem the AC compressor was functioning, the hesitation/surging at WOT didn't happen, I punched it three or four times on some back roads and it pulled perfectly. A few hours later and it was back. I'm stumped. I'm going to just have to wait until we can properly datalog it.

Thanks for the response, Terra, unfortunately I'm dealing with a turbo here not a belt driven supercharger.

 

It sounds to me like you have a wiring issue. I would reach in above the frame and wiggle the wires on top of the tank and see if you can get the pump to turn on and off.