adverseyaw

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adverseyaw last won the day on January 14

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About adverseyaw

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  • Location
    KBFI
  • Reg #
    N201XG
  • Model
    M20J

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  1. adverseyaw

    IO-360 misfires at idle and low MP

    I've been chasing the induction leak theory and have had some success so far. After changing the intake gaskets and o-rings, and cleaning up the Precise Flight standby vacuum line and valve, we got the popping to stop at much lower RPMs and get the mixture to richen way up (so much that it barely ran). Clearly, I had big leak(s). I'll be testing the sniffle valve again this weekend to see if that's leaking further air. We only have a few more possibilities. One thing that tipped me off is that I can only pull down to 12-13" MP with the throttle at idle and 600rpm. I found a few YouTube videos showing IO-360s pulling more vacuum at idle. It may be I can only get it this low but high numbers indicate a leak is possible (not guaranteed, but worth investigating).
  2. adverseyaw

    IO-360 misfires at idle and low MP

    That's a good idea. We pressurized the intake already and it held pretty well. Would the gaskets still be likely even if we've preformed this test?
  3. adverseyaw

    IO-360 misfires at idle and low MP

    An overall update: I stuffed a bolt into the sniffle drain valve tube and ziptie'd it there. Ran the engine up but still misses at idle. No change. The plugs are Champion RHM-38S fine wires. My A&P pulled them a few weeks ago and said they were all clean. I'll check the resistance on them soon.
  4. adverseyaw

    IO-360 misfires at idle and low MP

    Interesting. This engine has only 50 hours on it but getting extra air into the cylinder would do this. Good idea, will check. Interesting. The mags were overhauled 50 hours ago, but something was faulty with them causing no ability to start. The prior owner had them repaired right before I bought the plane. Could be a lingering issue with the mags. No problem with hot starts, but there is some occasional afterfiring at idle.
  5. adverseyaw

    IO-360 misfires at idle and low MP

    I think I've got enough to go on at this point. Checking the sniffle valve and sanity-checking the plugs is a good start. Done lots of runups on one mag at a time, no change so far (RPM drop, EGT rise, but no change in misfiring). Haven't looked at condensors, but will see what I can do there. These are all great ideas. Essentially we're eliminating variables in each system: fuel, air, spark. Getting your input helps me find new variables I may have overlooked, like the sniffle valve, which could read fine during a pressure test but could open after it gets jostled by a bit of extra fuel.
  6. adverseyaw

    IO-360 misfires at idle and low MP

    Good idea. The gauge reads well into the green and the problem is present with the boost pump running. Yep, it's there at all mixture settings. :-/ I had the flow divider cleaned, reassembled, and bench tested as part of cleaning the debris out of the fuel system. The problem was present before and after the cleaning, unfortunately.
  7. adverseyaw

    IO-360 misfires at idle and low MP

    Yes! This is very similar to what I'm experiencing. Definitely the first thing I'll check. We haven't cleaned out that valve yet. Will try the sniffle valve and will look at the induction gaskets too. We pressurized the intake and didn't find issues, so I'm not certain it will be a problem, but good to know. ;-) Plugs: will check those next. Not sure what's in there but will probably lose Champions if I find them in there. Air: sniffle valve is the best bet so far. Otherwise no leaks we've been able to find (nor staining -- my A&P has been pretty diligent about that since we cleaned the fuel system). EGT: the probe is in good shape, as it reads fine when we swap connections with another cylinder. The problem is in the line or a connector upstream of the wire bundle. Still working on tracking that down. Runup: yep, I do the EGT check for mags. Good suggestion, my A&P thought the same thing and checked this twice after the servo went back into the plane. We had it even at peak RPM at idle cutoff.
  8. adverseyaw

    IO-360 misfires at idle and low MP

    I don't know. The guy I bought the plane from had trouble with the overhauled servo and sent it out for repair, but I'm missing that document. It may need to go out again. (I would like to pinpoint the issue before sending the mag out, but it's certainly a possibility.) The 1000-1700 was me running the engine up. Any idle time in the trace is time when it was skipping. (In the entire trace I probably had 5 solid minutes of idling.) Good point. I haven't run across the 6/1 second setting in my EDM 830 but will look again and see what I can capture. Will do. We've leak-checked most if it. Good points -- will check into the 1-second setting and will continue to plug away at the EGT4. Interesting. Will look into this. Thanks all!
  9. adverseyaw

    IO-360 misfires at idle and low MP

    The problem occurred within a few seconds of engine start, and continued through the entire data log. The log is about 30 minutes long and the sputter probably happened a few hundred times, most noticeable at idle and at RPMs below 1700 or so. This is off of the Savvy website so could ask them. Getting details on the plugs like you suggested is probably a good first step though.
  10. adverseyaw

    IO-360 misfires at idle and low MP

    I'm running 10:1 compression pistons and do a lot of work to keep the CHTs in check. Unless timing 20 BTDC will adversely affect idle, it's probably a good discussion for another day :-) (Unfortunately the pistons aren't a variable I can change, and I haven't heard of more issues at idle, so for now I'm exploring what I can do with the other facilities on the engine.)
  11. adverseyaw

    IO-360 misfires at idle and low MP

    Went to 20 BTDC per Lycoming SB for reducing CHTs. Those are good suggestions. I actually don't know what plugs are on the plane. I'll check soon. Thanks!
  12. adverseyaw

    IO-360 misfires at idle and low MP

    Yeah, I did a bunch of searching before I posted. Found some threads but nothing that stuck. Most of the ideas were things I've tried. EDM data attached. My EGT4 connection is toast, so unfortunately that data is not useful. Blue line is fuel flow and green line is RPM.
  13. adverseyaw

    IO-360 misfires at idle and low MP

    This one, I take it? Am digging through now, thanks much.
  14. adverseyaw

    IO-360 misfires at idle and low MP

    Back when I was clogging injectors with debris, I was getting EGTs to peak 100-200 degrees on affected cylinders. I've only run it up twice since then, but no notable EGT changes since then.
  15. adverseyaw

    IO-360 misfires at idle and low MP

    I could be talked into that. That said, I've never experienced it on carbureted aircraft I've flown, nor the M20J I got my complex endorsement in. Do others encounter this as well?