Chocks

You might consider expanding your search to midbody's with TKS as well. Might give you some additional inventory of great Mooney's to choose from.

Thank you. I'll check this next. Otherwise, I have exhausted every other possibility I have researched. The "resolution" that I was given for now, was to keep the vacuum pump spooled up to just at 4lbs when it's hot out. That has worked flawlessly thus far. @carusoam thanks for the heads up on the "" issue. I have corrected that, and hopefully it will help with the search.

That is a good place to look. You're talking about the manifold pressure line through the firewall? If so, I'll have to find where the calibrated hole is and make sure I don't mess with it. The manifold pressure stays very constant, unless I lean the mixture, then I get the rpm rise and mp drop.

Still no resolution yet. No intake leaks found after the pressure test. Intake tube donut gaskets are fresh and supple. Replaced the collar gaskets with new just because they tore during tube removal. Issue is resolved when keeping the vacuum pump spooled up to anything above 4 during taxi/idle ops. I received some input from other drivers with the same engine and they all claim that is just a "Mooney Lycoming thing". I'm inclined to believe that, as I have flown that engine more than 200 hours in the last year, and there is no change or progression in the symptoms. Next will be to make sure I'm not sticking any valves when the engine is hot, double check the rebuilt items (fuel servo and mags) for any failures and probably change from massive plugs to fine wires and see how that goes. The search continues...

Just as an update, I also found a post from 2018 that was dealing with a very similar issue on a J. I believe that there is a malformed face on the intake tube on cylinder 2. That would explain the level EGT's but the cylinder running hotter and leaner than all the other cylinders even with a balanced fuel flow. The soapy water / air hose up the exhaust test showed no leaks. But that was with the engine cold. Also, I'm unsure the fluid test can be done on a hot engine as well. So I'm going to pull the intake for that cylinder and put one of the new oversized gaskets in it, and see what the result is. Will report back with updates. Link to earlier thread that helped with my issue:

That's right. It actually took longer to get the clamp off of the valve than it was to test. hehe. I actually replaced the valve, the fittings and the tube due to age, and to make sure it wasn't that. Good thinking!

Yes, I have the two metal tubes that come out of the back. Then I have an additional hole that takes about a 2" scat tube and it runs about a 14" length just open ended down to the fuel pump area. This is a really good area of investigation for me now. Just have to figure out a good process for testing.

I like all of these thoughts so far. I'll start checking fuel lines, connections and such for anything out of order. No leaks, drips or staining anywhere that I can see from the gascolater up to and around the engine. But I will check the lines from the senders into the belly if I get the guts up to pull interior panels. :\ Thanks @47Uand @Sixstring2k et all. @PT20JThe sniffle valve and the lines are all new and clamped tighter than a ducks butt. The fuel pressure gauge was changed out recently. The new one seems to vibrate the same as the old. So I just chalked it up to the "check it later" category. Looks like I need to revisit. A note on that though, my fuel level gauges do a very intermittent bounce sometimes, depending on the tank selected. I'll have to ponder that part. Thank you. @takairI never even thought of that cooling tube. I have a piece of scat tube that comes out of the back of the doghouse and just kind of points in that general direction. That would be interesting to see if there is a cooling issue with that engine driven pump... Hey @carusoam, yes the vac time does settle out above the 1200 rpm. That is something I or my A&P haven't worked through yet. I'm wondering if there is a crossover leak somewhere that would cause that inappropriate sync at low rpm, but haven't started asking yet.

Got a weird one: '64 E. IO360a1a. SMOH 150 Had this low rpm stumble before and after an engine overhaul. Worst occurrence in video link at bottom. Stumble creates RPM (100-200) drop and vacuum drop. Fuel pressure / CHT / EGT ok. Totally intermittent, but only happens when engine is hot after a medium-long range flight. Stumble only happens between idle and about 1200rpm. Completely subsides with power add. Only items out of norm are my #2 cyl runs about 40 degrees hotter than the other 3 - with balanced EGT, but recently on landing I'm noticing that #1 and #3 egt seem to drop off at landing idle. All runups, mag checks, and ignition checks ok. Troubleshooting completed: Engine overhaul in March 2022 about 150 hour in now. Overhauled: Fuel Servo, Flow Divider, Slick Mags New: Spark Plugs (gapped correctly), Plug wires, Boost Pump, Intake Boot, Sniffle Valve and tube Existing equipment: Gami Injectors/EDM 700 (no Fuel flow) Testing: Run boost pump during stumble Check mags for change per mag Change mixture settings during Open and close Ram air Cover Ram air port completely Checked intake gaskets and tubes Checked sniffle valve and line for leaks/loose connections Checked all metered fuel flows Checked spark Checked timing Adjusted idle cutoff Adjusted fuel flow Cleaned air filter Mag test after landing Ignition test after landing If I think of anything else, I'll edit this. Thanks for any help. Video of worst occurrence: https://vimeo.com/748591623

Nothing on the radar right now sir. You gonna move yours closer to show off your new AP?

Hey @N201MKTurbo, totally forgot to update you. Gauge worked perfect for what I needed. Thank you!

No rush. I’m having the fuel divider rebuilt anyway. And I doubt I’ll mess with it until after OSH. Let me know where to send you money when ready.

I'll take it if you haven't offloaded it yet. Let me know and I'll DM you my info.

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One of the smoothest, and beautiful landings you'll ever have in a short, mid or long body is a no flap landing over the threshold at 90kts. Now takeoffs in a Mid or long body are best with the appropriate TO flaps. Shorts handle fine with some or none. Loaded or not.