[Androids10guy]

Ok so I have an 01 s10 4door with a 4.3. I've been having an issue with a cylinder 6 misfire. It only presents itself with anything more than a gradual acceleration to cruising speed (55-60) or when pulling a trailer. I've changed spark plugs, wires, distributor cap and rotor, fuel pressure regulator, o2 sensors, done compression test, injector balance test, and checked for vacuum leaks and still NOTHING. I can't get this figured out and don't know where else to go with it. Has anyone else had or seen this problem before and if so what else can I do?!?!

 

[Rhotpursuit]

Let me guess...store branded parts. 4.3’s are picky about their ignition parts. OEM is your best bet. Before someone jumps me like a dog on a bone, you might get away with some brands, but the general spent a lot of time and money researching what works best.

 

[Rebel n Dirt]

I have spent 15 years behind the counter at 3 different auto part store chains, and I can say that @Rhotpursuit is right on the money. It seemed that AC Delco had the least problems with these crossfire caps, and the economy store brands had the most. If you cant get AC Delco, try getting Standard. Stay away from BWD, their quality has fallen pretty bad in the last few years. The shops now refer to them as "Broke When Delivered".

BTW, you will not usually be able to see the problem with the caps. It is caused by imperfections in the channels the cross bars travel through. There is only a mm or so between the post inside the cap and the wire post, and if that area has a bubble or imperfection then the spark will jump where it is not supposed to go.

 

[Androids10guy]

I have spent 15 years behind the counter at 3 different auto part store chains, and I can say that @Rhotpursuit is right on the money. It seemed that AC Delco had the least problems with these crossfire caps, and the economy store brands had the most. If you cant get AC Delco, try getting Standard. Stay away from BWD, their quality has fallen pretty bad in the last few years. The shops now refer to them as "Broke When Delivered".

BTW, you will not usually be able to see the problem with the caps. It is caused by imperfections in the channels the cross bars travel through. There is only a mm or so between the post inside the cap and the wire post, and if that area has a bubble or imperfection then the spark will jump where it is not supposed to go.

I get that and I'll probably give it a try since all I got to loose at this point is a few bucks but so far I've put 2 distributor caps both duralast gold and the problem never switched from cylinder 6. Maybe I'm just the unlucky guy who got two caps with the exact same defects but idk. Even still I'm gonna try an oem cap and maybe a few other things like maybe some upper engine seafoam. I'll try almost anything at this point. Thanks guys. @Rhotpursuit

 

[oldeerslayer]

Forget the Seafoam snake oil. It'll just make things worse. There is no such thing as a repair in a bottle.
You could also try doing a fuel pressure and leak down test.
Most LAPS "loan" fuel pressure testers.
Short version: Hook it to the test post in the fuel line near the distributor. Might have a plastic cap that needs to be removed. Turn key to on but don't start. Should read 60 psi and hold 55 psi for 10 minutes.
More complete how to:

HOW TO: Check regulated fuel pressure, pump max output...

HOW TO: Check regulated fuel pressure, pump max output, & leak-down‏ according to the GM shop manual If your vehicle has a driveability issue, the fuel delivery system should be the first thing on your list of things to check. Correct pressure, and the ability to hold the pressure, is critical...

www.s10forum.com

 

[Rebel n Dirt]

I wont speak bad about a specific part store chain... who knows I may end up working behind that counter one day myself, so I will say one thing I have noticed about Duralast, is they Dontalast very long. Cant say Master Pro is much better either... LOL. The only "store brand" that was of any good was from CSK back in the mid 90 with the Niehoff stuff. Niehoff was an economy brand here in the US but it was a premium brand in Europe, and it was good... then as all BWD companies seemed to go, quality fell off and well the rest is history.

 

[Jayhawke]

something to try- remove #6 plug and look at the seat and threads in the head with a strong light- any rust or discoloration there? a bad seat can cause ground issues .addtional, i did not see you state you have changed the dizzy- the bushings do where out.- as a few others on here have found out.remove cap and see if you have any wobble in the rotor- try picking it up and wobble too. ask here and i am sure everyone will help you find the right dizzy for a decent price.

 

[John S]

I think Jayhawke may be on the right track. I have a 2003 4.3. Recently had misfire cylinder 6. Ended up being the distributor. You could see the gear was clearly worn. The teeth were somewhat pointed on the ends rather than flat like they should be, resulting in excess play and poor timing. Certainly worth a few minutes to pull for inspection. Don't forget to mark distributor position.

 

[Androids10guy]

UPDATE. So I went ahead and put a oem distributor cap and rotor and just for the **** of it swapped out my wires again for a fresh set. The problem did improve. It doesn't happen to me under normal driving loads. BUT I haven't seen what it does pulling a trailer and it started misfiring on me when I got to interstate speeds. Gonna put my computer back on to see some live misfire data to see if it's still cylinder 6. If so, a new distributor will probably be my next move.