We have been having problems with my dads work truck. 5 and 8 skip like a bastid. We have swapped coils, changed plugs, checked valve springs, intake gaskets, wires, checked block grounds and all sorts of ****.

Anyone know what could be making just these 2 cylinders develop a skip? Its only with a slight load between 2,000 and 3500ish rpms.

Its starting to get old just looking for random things. Even with a scanner, nothing has turned up. Just a P0300. On a Snap-On scanner u can see them both miss fire.

Any help would be greatful.

 

Do an injector pulse test. Make sure the injectors are working properly and that the injector O-rings are holding.

 

just a thought but have you checked the fuel pressure?? i've had the same prob with my 99 and still have yet to figure it out, cept mine are cylinder 1 and 6.

 

yeah FP is 50psi with reg and 60psi before that.

 

Use the scan tool and ur fuel pressure gauge and prime each cylinder, pulse each injector individually and check their pressure. Each one shouldnt drop down more then 10psi. Chances are, the cylinders that are missfiring aren't holding pressure.