Truck hesitates or backfires when accelerating

I would check timing or spark plugs

Backfire often means lean fuel condition. Check for correct fuel pressure and report here.

check compression is it more then 10% difference between cylinders you have a leak also check for fouled plugs. wires fuel pressure, catalytic converter. i have the same problem in my lincoln its a leaking valve seat

wha is the make and model and year? please. how many miles on it?

TSB 91813 APR 91 Engine - Rough Idle/Hesitation/Backfire/Stalling

there will be codes stored so the scanner in use has not got the right protocols to read the ECM
Nissan products have to be set using a screw in the ECM to get to read the codes
you have to be specific with make , model , year , type of equipment to get closer

Sounds like a vacuum leak in the motor. Backfiring may be its own problem altogether. Backfiring only occurs when cold air is being introduced into a hot exhaust stream or when the timing is off. Check for vacuum leaks under the hood and leaks in your exhaust. If you have a leak in your exhaust it could be interfearing with your emission sensors and giving your motor false information.

A pop and hesitation is likely a backfire. The hesitation around 40 and 50 would be in keeping with that theory. There are several reasons you might be getting backfires and hesitation. If your ECM is adjusting the engine to run too rich this could happen. Misfiring might be occuring. Timing could be out. But one of the most likely is a restricted exhaust, likely due to a plugged, damaged or worn out catalytic converter. In some cases the converter may be bad enough to be giving you some performance problems, but not yet quite bad enough to signal an error. A vacuum test can help confirm whether this is exhaust related.

sounds like you have jumped a tooth on the timing if not timing out

sounds like a choke sticking or carburetor needing attention..(adjusting or rebuilding) hard to say more without hearing it my own self.....hit me up if i can help more [email protected]