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Chasing Misfire Gremlins; Cyls. 2, 4, 6, 8

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  #71  
Old 07-27-2021 | 08:44 AM
Extinct's Avatar
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Originally Posted by red99disco2
Currently my codes are P1300, P0305, P0307. There were a ton of codes before I did the plugs, wires, and O2s, mostly having to do with O2s and multiple misfires. I also haven't hardly moved it since completing the O2 work. Do I need to do some driving for those to gather more data and update? I've been nervous to drive with as bad as its idling and misfiring.
When you have paired misfire code, first thing to check is if you have the two wires swapped location wise. Normally the engine will barely run at all if you have two swapped.

You can monitor fuel mixture using the oxygen sensor voltage once it is running. Close to one volt is rich, close to zero volts is lean.

I have found the best way to troubleshoot is swap known good for suspected bad. Misfire on the 5 and 7? Swap plugs with 1 and 3 and see if it follows the plugs. Then do the wires (will need to be 8 and 6 but you get the point). Then do the coils. Then do the injectors.

Sometimes general rough running can be traced to the MAF which you can test by unplugging it, but that generally does not manifest by throwing specific cylinder codes.
 
  #72  
Old 07-28-2021 | 06:13 AM
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From: Birmingham, AL
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Just stumbled across this post and wanted to comment for the benefit of the future reader…

I had an almost identical issue but a much more severe misfire. I installed reman injectors from a seemingly reputable eBay store to try and fix some lean codes that I had had for a while.

Long story short: do not buy cheap remanufactured fuel injectors from Ebay. The injector that went in the #3 cylinder was faulty, failed wide open, and flooded the cylinder with fuel. Just like the OP it still took a while to diagnose, until it hydrolocked the engine. Luckily I shut off the motor as soon as I saw the flashing SES light and super rough driving.

I almost ended up destroying my motor and spending more time and money than was ever necessary simply because I bought the cheap $75 (for all 8!) injectors.

$300 and genuine Bosch injectors later the truck was running perfectly. My lean codes weren’t even related to the injectors, we found a vacuum leak elsewhere eventually.

Moral of the story, not only is throwing parts at it expensive, it does not help diagnose the root cause of the issue. Only replace parts when you have done everything possible to troubleshoot the problem. Then buy good parts.
 
  #73  
Old 07-30-2021 | 01:18 PM
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From: Idaho, USA
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Thanks! I will triple check wires and plugs. Before I did all the plugs/wires/sensors work I was getting codes for all Odd numbered cylinders but so far it's reduced to only 5&7. If a coil fails can it partially fail or would it fail as a unit? 5 & 7 are on different coils so I don't understand those failing unless they can fail partially. I admit my ignorance in all things automotive here, I'm doing as thorough research as possible and doing the work myself. On the Torque app specifically, what readings can I check for to help diagnose or potentially rule out certain factors? When idling parked should the O2 voltage readings be cycling rich/lean or maintaining steady readouts in the middle? I'd like to do a compression test soon after checking the plugs/wires, are the harbor freight or cheaper amazon kits worth the buy? I'm nervous to drive it as far as my nearest mechanic. I just put SeaFoam in the tank to hopefully help clean the system, it's been a while since I've run it through a round of that.

Thanks everyone for the input, its super helpful!

Originally Posted by Extinct
When you have paired misfire code, first thing to check is if you have the two wires swapped location wise. Normally the engine will barely run at all if you have two swapped.

You can monitor fuel mixture using the oxygen sensor voltage once it is running. Close to one volt is rich, close to zero volts is lean.

I have found the best way to troubleshoot is swap known good for suspected bad. Misfire on the 5 and 7? Swap plugs with 1 and 3 and see if it follows the plugs. Then do the wires (will need to be 8 and 6 but you get the point). Then do the coils. Then do the injectors.

Sometimes general rough running can be traced to the MAF which you can test by unplugging it, but that generally does not manifest by throwing specific cylinder codes.
 
  #74  
Old 07-30-2021 | 02:12 PM
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Coils can fail partially. Each oil is actually a siamesed coil with two wires being fired by one half of each coil. so 2& 8 are paired, 3&5, 1&7, 4&6. Although they can fail partially with only #5 failing on that coil, usually the paired cylinder fails quickly behind it. If you have confirmed you have the wires installed in the correct locations you can swap coils left to right and if it is the coil the #5 misfire will move to #6 and the #7 will go to #8 if the coils are bad.

Start with swapping plugs from 3 to 5 and 1 to 7. If it stays the same check compression on every cylinder on that side. You could have a blown HG between 5 and 7 and no/low compression on both cylinders. If you prefer working on it to driving to the auto parts store or ordering a compression tester from Amazon swap plug wires 7 to 8 and 5 to 6. If it stays the same swap coils left to right. If it stays the same swap injectors 5 and 7 to 1 and 3.

Oxygen sensors should be cycling at all times. If you have close to zero volts it is either lean due to bad injectors, bad maf, or bad sensor. Constant near one volt means your injector is stuck open or MAF is bad.

Report back your findings and we will go from there.

 
  #75  
Old 08-14-2021 | 07:23 PM
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From: Idaho, USA
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Sorry for the delay, it's been a busy past two weeks for me! I just did a compression test today, have not gotten to swapping wires/coils/etc.
Cyl. 1: warm 140, wet 165 Cyl. 2: warm 140, wet 160
Cyl. 3: warm 140, wet 150 Cyl. 4: warm 130, wet 145
Cyl. 5: warm 135, wet 150 Cyl. 6: warm 140, wet 155
Cyl. 7: warm 135, wet 145 Cyl. 8: warm 145, wet 150

Warm span: 135 - 145, wet: 130 - 160

Thoughts? Am I wrong to feel this is low compression all around?
Current codes are multiple misfire, and cylinders 1, 5, & 7. If I'm not mistaken, I believe that's 3 different halves of the 2 coils so is it safe to not have the coils as a primary suspect? Any thoughts to the timing belt?
 
  #76  
Old 08-14-2021 | 08:51 PM
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From: Lynchburg VA
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Compression looks fine. 1 and 7 are on the same coil. Do the plug swap like I recommended.
 
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