Cylinder 3 & 6 misfire

BlackMagnum2000 · Dec 20, 2014

Alright so earlier in the week I upped my tune on my Superchips and it threw me those codes. Now I thought it was fine after I put it back down to an 87 tune until it just gave me these codes again.

Background. Every ignition piece is new. Plugs, wires, distributor, button, rotor, cap, coil, cam and crank sensors. Ever since I rebuilt the engine, it seemed like it has been missing at around 1,500-2,500 RPM. Hooked it to a Snap on and it detected no misfires at all. So I've driven it for a while now (1,000 miles? Maybe 2?) and this has just started happening

rowdyram · Dec 20, 2014

Because 3&6 are sequential in the firing order my first thought is a cross firing cap or a plug wire(s) not routed correctly ie too close to exhaust. Also because the are sequential a severe mis on #3 can cause a #6 DTC even though its not missing

BlackMagnum2000 · Dec 20, 2014

rowdyram said:
Because 3&6 are sequential in the firing order my first thought is a cross firing cap or a plug wire(s) not routed correctly ie too close to exhaust. Also because the are sequential a severe mis on #3 can cause a #6 DTC even though its not missing

What would cause the cap to cross fire exactly? The wires/connections to the cap all are insulted pretty well and are pressed all the way down.

I'll look into the wire routing tomorrow. I don't think we paid close attention to that when we put the engine in honestly

rowdyram · Dec 20, 2014

Sometimes the plastic castings in the cap don't come out thick enough and spark jumps between posts inside the cap. If you look inside there is usually carbon tracking. This will look like small black lines almost like cracks. Can be hard to see if your cap is black.

BlackMagnum2000 · Dec 20, 2014

rowdyram said:
Sometimes the plastic castings in the cap don't come out thick enough and spark jumps between posts inside the cap. If you look inside there is usually carbon tracking. This will look like small black lines almost like cracks. Can be hard to see if your cap is black.

Well my cap is bright blue but its not exactly easy to inspect being so far back. But I'll see what I can do to look at it. thanks bud I appreciate it

rowdyram · Dec 20, 2014

As far as checking the wires.. Closing the hood almost all the way and peeking in while running you can sometimes see spark jumping if not a spray bottle with water, sprayed down the wires will also help

BlackMagnum2000 · Dec 20, 2014

What exactly is the water for??

rowdyram · Dec 20, 2014

Increases conductivity and causes spark to jump easier making a voltage leak stand out. If your miss is 1500-2500 it probably won't show at idle without some help. If you spray it down and there is a leak you'll either see it or it will cause a misfire. If it causes a miss spray that spot a few times to verify then shut it off and inspect that spot.

BlackMagnum2000 · Dec 20, 2014

Alright thanks. I'll look into it tomorrow

dodge dude94 · Dec 21, 2014

Rowdy is onto something there. After you do the water check, get yer skinny ass up there ( :bleh:

) and pull the cap and rotor out and inspect them.

BlackMagnum2000 · Dec 21, 2014

dodge dude94 said:
Rowdy is onto something there. After you do the water check, get yer skinny ass up there ( ) and pull the cap and rotor out and inspect them.

I'll probably replace plugs 3 and 6, swap out 3 and 6 wires with some spare I have, then water check, check the cap, then re-route. Not sure when I'll be able to get to it though.
My bet is probably on the routing honestly

BlackMagnum2000 · Dec 24, 2014

Alright brand new Bosch Super Plus Coppers and MSD 8.5 mm wires as suggest by Merc225hp. Gapped to .035.
Cranked fine. Didn't run it for long as I didn't have my intake on. No codes, but the codes only happened twice and kinda far in between.
Still is stumbling/missing between 1,000 and 2,000 RPM. Almost seems to be doing it even harder. Really getting confused here..
Routed the coil wire far from all the other plug wires. And any plug wires that crosses did so at a 90° angle, and they all have wire loom around all crosses.
I checked the cap, looked good. Also the spark plugs that came out looked good too.

BlackMagnum2000 · Dec 24, 2014

Any chance I got a bad MAP sensor (replaced maybe 9 months ago) ?

dodge dude94 · Dec 24, 2014

Have you done a compression test?

BlackMagnum2000 · Dec 24, 2014

"Hey dad do we have a compression tester?"
"You won't have low compression"
"But do we have one?"
"No, and don't bother"

dodge dude94 · Dec 24, 2014

BlackMagnum2000 said:
"Hey dad do we have a compression tester?"
"You won't have low compression"
"But do we have one?"
"No, and don't bother"

Considering how ignorant he is at times, drag your skinny ass to the parts house and rent a compression tester and test the compression.

BlackMagnum2000 · Dec 24, 2014

dodge dude94 said:
Considering how ignorant he is at times, drag your skinny ass to the parts house and rent a compression tester and test the compression.

Problem is he's off work tomorrow and I'll definitely hear it from him if I do that. Honestly I don't see why it would be off though. What are you thinking, intake mani leak?

BlackMagnum2000 · Dec 24, 2014

My truck is like ten times more moody and ****** than my girlfriend

dodge dude94 · Dec 24, 2014

BlackMagnum2000 said:
Problem is he's off work tomorrow and I'll definitely hear it from him if I do that. Honestly I don't see why it would be off though. What are you thinking, intake mani leak?

lol **** that guy! Do it anyway! :flipthebird:

We've proven him wrong more than once. Spending money on the ignition means nothing if you've got other problems...like oh...say a BURNT VALVE. :crazy:

BlackMagnum2000 said:
My truck is like ten times more moody and ****** than my girlfriend

Daaaaaaaamn :uhoh2:

BlackMagnum2000 · Dec 24, 2014

dodge dude94 said:
lol **** that guy! Do it anyway! We've proven him wrong more than once. Spending money on the ignition means nothing if you've got other problems...like oh...say a BURNT VALVE.

Daaaaaaaamn

You think one of my brand new valves is burnt?

Cylinder 3 & 6 misfire

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