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I've got a buddy with a '99 K1500 RCSB 4.3 V6, it's stone stock and has about 150,000 on it. It is misfiring under load, especially climbing hills. It flashes the SES light and throws a code when it does this stating "Random / Multiple Misfires". We replaced the cap and rotor today and it didn't help. He put new e3 plugs in it about six months ago trying to fix the problem. I'm out of ideas any help would be appreciated.
:thanks: in advance.
Vacuum leaks, o2 sensors are the most common problems I've run into.
why not put some orignal a/c plugs back in it, since its all stock
i had the same problem and it ended up being a plugged cat.
run a compression test.if it is stock i would put ac plugs in it.ck for vacuum leaks.put a good set of plug wires on it
+1 on the plug wires..sounds like secondary ignition problem
Thanks for all the input we will start trying what you guys have said. I was thinking plug wires too but didnt want to just keep throwing parts at the thing.
Could have had a bad plug originally, then when he installed the new plugs, he could have cracked one, it's very easy to do and sometimes you won't even notice it. it won't hurt to check them again.
that many miles, original plug wires?
Get it on a scanner and see which cylinders are misfiring or if all of them. That will greatly narrow down the problems it could be.
Definately sounds like a plugged cat. Put it in drive step on the brake and rev it up without spinning the tires. Open the door and point your ear towards the ground underneath the truck. You should be able to differentiate the misfire sound between an engine issue or it being choked up with exhaust. If he has never put cats on it look no further. ASE Certified here.