Multiple Misfires

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dapepper9

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Cam pickup and magnetic crank pickup are used together to determine location and speed of engine and pcm uses that to time it
 
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jalbin

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Update

So I did the plenum gasket and everything that goes along with that. I see either very little or no change. I hace to drive it around some more to get the codes, but it feels like they are going to be the same. Replacing the upstream O2 sensor today. Am I still experiencing some kind of vacuum leak? If not, what else could be causing this issue?
 

dudeman2009

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So I did the plenum gasket and everything that goes along with that. I see either very little or no change. I hace to drive it around some more to get the codes, but it feels like they are going to be the same. Replacing the upstream O2 sensor today. Am I still experiencing some kind of vacuum leak? If not, what else could be causing this issue?

Well, you've checked the ignition coil, replaces the plugs and wires. I don't remember if you did the cap and rotor. Plenum is done, O2 is replaced. Vacuum leaks won't cause misfires on the magnum engines. At this point i'd check cylinder compression, that can cause similar symptoms to misfiring.

You can also check the wires leading to the fuel injectors. If those are bad or even the injectors, that can cause misfires. A fuel pressure test at the rail is something to try. It should be about 50psi +/- 5psi at idle, I don't remember for under load. It should never drop below 30psi though.
 
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jalbin

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I haven't done the cap and rotor. I need to check fuel pressure at the rails and I need to get a leak-down gauge from somewhere. I read that a dirty fuel filter will cause issues, but you'll only see them under load. I haven't checked the EGR either.
 

dudeman2009

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I haven't done the cap and rotor. I need to check fuel pressure at the rails and I need to get a leak-down gauge from somewhere. I read that a dirty fuel filter will cause issues, but you'll only see them under load. I haven't checked the EGR either.

Check the cap and rotor next, if those are just horrid, that would cause your problem.
 
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jalbin

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Update

Good call reminding me about the distributor cap. It had a messed up contact and take a look at the wires going to the pickup coil! Could THAT cause the misfires? (Are YOU my mother?)
 

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dudeman2009

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Good call reminding me about the distributor cap. It had a messed up contact and take a look at the wires going to the pickup coil! Could THAT cause the misfires? (Are YOU my mother?)

I'd try just cap and rotor first. If that doesn't fix your problem, then you'll probably be replacing the Cam sensor, but when you do, you'll mess up the fuel sync and need to get it reset.

Edit: Forget the bit about the fuel sync, my cam sensor was kind of busted but I wasn't aware of it and thought it was normal.
 
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dapepper9

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Won't mess up fuel sync unless you spin the distributor which there's no reason to for that plate. All you do is pop the rotor off and lift the plate up. New plate fits in the distributor 1 way
 

ADudeOnSkis

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I drove around for a year with a bad upstream 02 before it coded. Test it or just change it. Use oem or nkg.
 

Shadow_Death

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If you go NKG make sure you get one with the correct length cable too.

Lessons learned the hard way. :/
 
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jalbin

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Late Update

So I have replaced the distributor cap and rotor, cam sensor, upstream O2 sensor, and a bunch of little vacuum lines (not the problem, I know) but the truck is still shooting misfire codes and idling rough.
 

regularcab2500

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Have you performed the leak down test or resistance tested the fuel injectors yet? Also, how many miles are on this truck?

Sent from my SM-G930V using Tapatalk
 

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