Limp(s) and "invisible" limp
I need to learn more about limp mode one these trucks. First of all, is it true that only fuel and transmission issues can cause it? For example, if a wiring problem causes limp, is it because it makes the computer "thinks" it has a fuel or tranny problem?
The reason I ask is because I had a customer with a LiLY that began to experience limp increasingly after a good tune and I kept telling him it was the filter until we found out some of the injector harness was rubbing and grounding out on a bracket (there is a bulletin on it). But why did he start experiencing it more after the tune? Is it because with more power and driven more aggressively it flexes the harness more, or could it be something in the tune makes it more sensitive to reporting the failiure?? (not on purpose). I would think either the first one or since there is more demand for fuel it fails more often?
Also, how about disabling limp mode? I know the safeguards are there for good reason and a little wear has already occurred by the time it limps, but decreasing the occurrence would improve drive-ability and satisfaction for the customers while they are saving up for say a lift pump or a torque converter.
Finally, what are the likely causes of the invisible "limps" or hesitations that do not set check engine lights or codes. I suspect defuel, no? I used run a smooth tune that would fall on its face and hit a wall for a second in the higher gears every once in a blue moon, like monthly. Never flashed the PRNDL or MIL, and no 700 or 87 codes.
I know very well that logging can and will give me more info on this when it comes to specific trucks, just looking for general ideas. And what should I log? Thanks!!!
