Random misfire

[matuva]

I'm not very used in chevy gassers. though, I accepted to help a buddy who owns a 1998 K1500 with a 5.l Vortec engine.

The truck starts fine and purr like a kitten at iddle. Though, when driving, it starts to stumble a bit once we reach 2 000 rpms and the MIL comes on.

I hooked my scanner and it said "random cylinder misfire" :skep:

Fuel pump is Ok, new spark plugs, new spark plug cables... :???:

any suggestion? We have ordered a new ignition distributor cap in case...

 

[THEFERMANATOR]

Those trucks had ALOT of issues with the cap and rotor causing all kinds of misfires and problems. Only run the GOOD marine grade caps or premium caps in them. The cheapos are made from a light duty plastic that is known to burn through in just a few minutes of running. Also the distributor gear is another problem prone area in those trucks. It is rumored that GM got some bad gears that weren't mellonized properly, and the roller camshaft gear would chew the distributor gear and wear it down to just sharp nubs left. Over time it gets so bad the timing will jump teeth and misfire. ONLY run AC DELCO platinum or iridium plugs. I've tried numerous other plugs in them, and all the rest always misfired on me under load. And finally the origanal central injection setup with poppets was another known weak area to cause all kinds of issues. GM in 01 came out with an upgraded unit that replaced the central injection poppet setup with a multi port sequential injection setup with individual injectors at the ends of the hoses. it was a HUGE improvement in driveability for them.

 

[matuva]

The cap is on the way... but I forgot to order the rotor :twak:

 

[Diesel Nut]

I have seen this a couple times. If the cap and rotor does not help, Change the distributor. I have changed the distributor, cap, and rotor and it took car of the problem. The distributor sends the cam signal.