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Roger Rogers

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About Roger Rogers

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    2014 Sierra Z71

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  1. I've done this. It's interesting. The idle gets better. Didn't go away entirely, like when I cleaned all the intakes and exposed parts of the valve. But it's not much different. I think it's just better for now and then I feel like the computer starts trying to learn how to solve the misfire issue and things get worse. I'm a noob mechanic, but the fact that the misfire could go away entirely, even if for 20 minutes of idling, and always when at highway speeds, would seem like the cam shaft isn't a problem, right? The misfire code is 100% consistently 0305 (cylinder 5).
  2. Hi @CrawlSlow, thanks for chiming in. No mods or tune before code. Never been done at all.
  3. Well, I spoke too soon. The misfire is back. So strange, because it entirely disappeared for about 100 miles. I could idle with no misfires, but it's now back to misfiring at idle. To recap: At idle I will get about 150 misfires per minute (using OBD2) At highway speeds the misfires disappear entirely (OBD2 still connected) When idling the misfires appear to grow in intensity over time. Check engine light will come on eventually and I've had the traction warning appear as well. Replaced coil packs, plugs, wires, injectors Compression test on the misf
  4. Well, I had to try one more thing... I took off the manifold and walnut blasted the intakes. The actual intakes didn't look bad, but where the valve seat was gunky and I used seafoam to clean that up as best I could. No more misfires! I didn't realize these engines were so finicky about carbon build-up. It really didn't look bad, definitely not as bad as many pics I've seen, but apparently it matters! To think the solution suggested was to change the engine. Definitely got me thinking about installing a catch can (though, I've only heard about them and need to read up a bit more).
  5. Hey @BigBadSierra, as you say, that was the first thing I tried. Coil pack, wire, plug. No joy. Next compression test, which was solid. Last thing I did was injectors. The intake ports had some carbon build up, but didn't seem bad at all. Have a hard time believing that is the cause, but I'm thinking to take the manifold off and doing a cleaning and walnut shell blasting the intake ports. Just can't believe that would be the problem.
  6. Yeah, I'm kinda thinking of just doing that. If it dies then I drop a new one in. It just feels like something small is going on. The cylinder has great compression - same as the others in the bank.
  7. I hear you. I did take to a shop and just looking at the code, and the miles (220k!) they immediately went to dropping in a new engine. I'm prepared for that possibility, but the truck is almost all highway miles and in excellent condition otherwise. The only problem is this P0305 at idle and goes away when accelerating / driving. I'm afraid I'm going to get similar response wherever I go, or a lot of parts swapping and then drop a new engine, so trying what I can myself before then. Maybe I'm at the end of the road with this and I don't want to run too much if it's going to damage
  8. Just tried. No sound of back pressure. Granted, the truck is almost empty at present. Should there be? BTW, really appreciate your feedback!
  9. Sorry, I don't think I understood what you were asking. No special tune. This is all factory tune. Is that what you mean?
  10. Ok, I did a hack vacuum leak test using a cigar. No smoke came out anywhere. It seems tight. A few more details: This problem is most noticeable at idle. Acceleration is good and if I am running on the highway a lot (not stopping at lights, etc., meaning not idling, the light eventually will go away. This tells me that when above idle the misfire is happening much less (feel free to correct my thinking). So I'm at a loss. Could this be a sticky lifter/valve? Would this happen only at idle?
  11. Hi @CrawlSlow, I think so. Plugs look good and plug, wire and coil pack on that cylinder have been changed. Oil always changed and is clean. Anything else?
  12. Well, changed all the spark plugs and... I'm still getting 0305 misfire in cylinder 5. Bah! I did find a P219A code. I think this happened once. Not sure if it's recent and I've now cleared the codes in trying to make sure I was in fact still getting a 0305 misfire, which, after waiting a while, showed up again. What next? Any ideas would be much appreciated.
  13. Ok, just pulled all plugs on that bank and retested. I also watched a video on compression testing and learned that I need to turn the engine over about 4 times. I was just doing once before. This resulted in higher values: Cylinder 1: 205 Cylinder 3: 195 Cylinder 5: 198 Cylinder 7: 190 Cylinder 7 is hard to reach so I couldn't tighten the tester as well, whereas cylinder 1 is easiest and I could tighten it properly. I think that could be a reason for the slightly lower values toward the back. That said, the values seem pretty good and consistent, right?
  14. I'm just re-reading your post and realize I only ran on two cylinders and you suggest on the entire bank. I thought I would run on the two non AFM cylinders, but I suppose I should compare across the bank. I'll redo and report back.
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