I've been trying to get my truck tuned, but it's been giving me hell every step of the way. Was told something is wrong mechanically, but the issue still persists after confirming everything was good to go. My issue is, when I try to make a run, the truck will pull well, then it will, at random rpm points, start stuttering and coughing. During this stuttering and coughing, the wideband shows that afr's are way lean. Up until the coughing starts, afr's are fine. I would assume that this would indicate spark blow out, but plugs are gapped at .020". I have fought and fought with this truck and can't seem to get it to clean up. Could I have a weak ignition coil or three? I've always heard that the LS coils are nearly indestructible, but what else could it be?

The truck is a late 2007 4.8L with a precision 7475 turbo, magnafuel 750 fuel pump, 160lb injectors...

Any help is greatly appreciated. If you need more info on the truck please ask.

Thanks in advance.

 

I would check your fuel pressure. Just hook a gauge up to it when you are making a run, and see if it drops off.

What injectors are you using? are they the newer Bosch 160lb injectors?

 

Fuel pressure is good, I have a gauge on the pillar. I have a boost referenced fpr, and fuel pressure goes up and down with boost like it should. Fuel system is custom. All the stock stuff is gone. Injectors are 160lb units from FIC. Bought them about a year ago. Maybe a year and a half.

 

May be silly but do you have more then 1/4 tank of gas? If I have less than 1/4 and I step on it my truck stutters I guess the force takes the gas to the back and robs the pump causing it to stumble

 

I'm running a sumped fuel cell.

 

Is the fuel cell in the bed with the pump under it? Is the cell adequately vented for what the 750 is pulling? How is the FPR plumbed?

 

Swapping out some coils wouldnt hurt to test.

 

Have you posted your tune and log file(s) somewhere?

 

Do both banks go lean when this occurs?

What method did you use for the 80e swap?

 

Do you have a log of afr during a pull? Does it clear up as you get to higher rpms or does it get worse the higher you rev?