Roger Rogers

ha! I thought so too. Replaced all injectors.

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). Is there any possibility this is actually a more random misfire, but being attributed to only one cylinder, or the cylinder is wrong? Cylinder 5 isn't AFM, so my understanding is that it is much less likely to have a collapsed lifter. But then, the problem doesn't seem to indicate that anyway... so. Next things I'm going to try unless someone tells me DON'T DO THAT!: - Run Marvel Mystery Oil in the oil for 500 miles - Pop open the valve cover on cylinder 5 bank and see if anything is sticking, etc

Hi @CrawlSlow, thanks for chiming in. No mods or tune before code. Never been done at all.

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 misfiring cylinder is excellent and same as the other cylinders Cleaned the intakes carefully (I cleaned with walnut shell blasting and then seafoam with a brush on the valve stem and valve opening), and after doing so the misfire disappeared entirely... for about 100 miles, or about 10-20 minutes of idling... I idled a lot just because I was so amazed that the problem was gone I was (happily) surprised that the cleaning had an effect, sadly, it didn't last long. This makes me wonder if I'm having a problem with the lifters/springs? Maybe the valve in this cylinder isn't sealing tightly/quickly? I'm probably talking gibberish, as this is by far the most I've ever worked on a modern 4 stroke engine. As KARNUT says, I should probably take to another shop, but the high miles (220k) seems to make them go towards replacement and I feel this engine has a lot of life left on it. It runs great at highway speeds and under load and the cylinder compression tests are all basically at factory specs.

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). Clearly oil vapor going through the intakes without the gas acting as solvent is not helping things. One bummer in this whole process is that after I changed my fuel injectors the MPG has dropped I would say 2-3 MPG. I'll start a separate thread on that... not sure if they need to settle in for MPG to rebound or if the compatibility chart I looked at isn't accurate. Thank you everyone on this thread for giving advice. Much appreciated!

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.

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.

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 my catalytic converters, etc. Any other things to try I'd really appreciate. Was thinking to pop the valve cover to see if anything is sticking for that cylinder.

Just tried. No sound of back pressure. Granted, the truck is almost empty at present. Should there be? BTW, really appreciate your feedback!

Sorry, I don't think I understood what you were asking. No special tune. This is all factory tune. Is that what you mean?

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?

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?

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.

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? To recap what's been done so far: plugs, wires, coil pack on cylinder 5. Going to order a fuel injector next.

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.

Ran compression test on cylinders 3 and 5 and I'm getting exactly the same compression from each (~140 psi). It might be slightly higher, as I couldn't screw in the tester more than hand tight. While not high, that seems decent, right?

I've borrowed a compression tester, so I'm going to try that next and will let you know how that goes.

Hey y'all. Just joining this forum. Seems like a great community! My post title pretty much states the issue. It started in the past few months. Symptoms: Mild rough idle, gets better with increased RPM - or maybe is just drowned out. Sometimes shows code O305. Already done: change plugs, wires, coil pack. Considering: pressure test, fuel injector replace, maybe isolated manifold leak? Of course, also dreaded collapsed lifter Have read quite a few posts on this issue already, many point to AFM. However, wondering, does AFM affect cylinder 5? I didn't think so, unless something changed in 2014? Even if not, would you suspect collapsed lifter anyway? Any other thoughts? The symptoms are mild at present, but I'd like to address sooner than later if that can help avoid (further?) engine damage. Would appreciate any thoughts at all. This engine has high miles, but they are highway and I'd love to keep it going. Cheers!