Riddle me this. 3rd gen welcome

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Bigtman07

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Ok guys I have an interesting problem that I am still trying to track down and need some extra advice. A while back I was going to a truck show up north some of you may have seen my thread on the other place. But anywho on the way up I found that one of my electrodes broke off in the cylinder. I couldn't change it till I got home. On my way home the truck started to lack power and was thrown engine codes left and right but only one of them stuck. P0307. Cylinder 7 misfire. Ok changed the plug and cleared the code thought all was good. Couple days later it came back same code. Checked plug again it was loose screwed it in cleared the code. Next day back again. Ok checked it again loose??? No ok so switched wires on 5 and 7 thinking I accidently crossed the wires when I replaced them. Cleared the code and it ran like crap. Ok switch wires back all was fine. Made sure code was gone. Next day same thing. ok Fine I'll change the cap and rotor. Did that cleared code again. # days later back on again. Ok Thinking injectors. Changed the injectors around to see if the miss follows the injector. Nope still the same cylinder. Ok I was thinking sludge weak spring carbon buildup. Got some seafoam and foamed up the truck. **** gone for about a month. All of a sudden its back. But this time the truck runs funny on a cold start. Just like it's missing. Give it some gas clears right out no big. But what would cause such a random misfire and would go away after seafoam??? I'm a little confused.
 
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Bigtman07

Bigtman07

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When I did my plenum about 4 or 5 months ago i took it off and gave it a total cleaning and it still looks the same. I ran some seafoam through it last night so we'll see how that goes. Ran really smooth right after so who knows.
 
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Bigtman07

Bigtman07

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Sounds good. No rattles shakes or anything like that. No pressure loss.
 

Laramie1997

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Sure you didn't nick the plenum gasket when you installed the new one? Very easy to do and it will cause those problems.
 
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Bigtman07

Bigtman07

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Pretty sure. But of course I don't know for sure.
 

Laramie1997

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....


Locate a temp gun (IR) and check the cat. If the temps coming out of the cat housing are NOT higher than what they are going in, then you have a problem with it. Rattles aren't a tell tell sign that you have a problem. Neither is a pressure test.
 
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Bigtman07

Bigtman07

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uh huh interesting. Will do. I'll check on that. Thanks for the extra advice Chris.
 

Laramie1997

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Yes, we have plug wires. Unlike you though, we do not have coil packs. We still operate on a cap and rotor system. Had it been a bad wire, the problem would have chased when he moved it. IE, swapping 5 wire and 7 wire. If the wire was the problem, his misfire would have moved to cylinder 5 and 7 would have been fine.

As has been stated, common problems within a cylinder misfire on 7 is usually the plenum and or the cat. Being that he DID have a blown plenum gasket, I still conclude that the cat is getting flaky along with the pre-cat O2 sensor. The sensor itself shouldn't cause the misfire as on its own however.

Tony, just a reminder, those plenum fixes don't always work. That Al plate does fix the visual problem, but I have been seeing where rams with that fix have gone another 10-20K miles and the gasket is blown again. The difference is where the pressures go to. These gasket failures on the new Al plate usually move further up in the kegger and typically, you wont be able to see it with a visual inspection.

Hence why I never jumped on the bandwagon and swapped mine out. I'll just throw a gasket in it and call it day.
 
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Bigtman07

Bigtman07

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uh huh. Well Sounds like I need to pull the keggar again and take a look huh. I am getting a new exhaust some time soon and will remove the cat so maybe that will help.
 
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