The International Cessna^® 170 Association

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Sounds like water in the fuel! Was it Avgas or Mogas? I noticed you didn't switch tanks when it started to run rough, or at least you didn't mention it.
I'm assuming you did drain the sumps throughly after re-fueling, of course...

A few years ago, with my good friend Russ Platt we were flying the Piedmont Airlines DC-3 at an air show when BOTH engines started to run rough! I looked at him, he looked at me, and we both asked the same question...you did drain the sumps, didn't you? "I thought you did!" That's what happens when two captains fly together.

Old joke: The three most dangerous things in aviation - A doctor in a Bonanza, two airline captains in a Cessna 172, and a flight attendant with a -
(decorum dictates I don't finish this one...well, it was funny in 1977!)

I let a friend borrow my 170 the other day - he's the only person I trust with it (tons of tailwheel time, a Citation captain and unfortunately a furloughed US Airways pilot I used to fly with).

After using 43A, he topped it off with Mogas, using five gallon jugs. A few days later, I drained almost a quart of water from the right tank! Same station I fill my Mogas trailer from; BP. Sometimes the tanker will stir things up after filling the underground tanks. He's as perplexed as I am.
BTW, it is hangared, so it can't be rain water.

Something to consider; what do you think? Russ Farris

I've had an in flight stuck valve and the symptons where just like you are describing. I didn't fly for 30 minutes after it stuck, was lucky, and had a place to put down so I don't know if the valve would have unstuck itself or not in my case. It seems possible that a valve could come unstuck while flying. Carb heat, leaning, etc has little affect and it does feel like the engine is going to leave the aircraft. Most people tell me that valves stick on the ground during runup and they have never heard of an inflight valve sticking, it has happened to me more than once. One really weird thing is that the plane will not idle back to low RPM when a valve sticks, not sure why that is. During the landings now when it happens I cut the engine off with mixture control once I have the runway made, start it back up to taxi off the active. Am sure that different problems can have the same symptons and am not saying that you had a stuck valve, but it is possible, and it would be hard to diagnose if that's what it was and now it is unstuck. It might stick again, and it might go several hundred hours without sticking if that's what it is.

I had the problem in an 0200 in a C140. The rocker shaft bushings were VERY worn, enough to cock the rockers and leave asymetric marks on the bosses. My theory is that the cylinder got hot and the valve stuck. After a few minutes of cooling the valve freed up and the cylinder ran fine for a while. The cycle repeated at about 15 minute intervals.

My guess is a sticking valve. If it were water in fuel I'm not sure it would run rough for 30 min as the water would almost have to be in suspension to do that. When you switch mags and notice little change it tends to eliminate the plugs/ignition. You tried carb heat with little difference so that rules out air problems. Probably a valve.

When my engine went to the shop last week I had a chance to talk to the Cyl expert for some time. He has seen a bunch (in the thousands) of cyls and he said it is almost a given that Cont C-145/0-300 and 0-200 exhaust guides would be tight. He has no explanation but says he sees it all the time. It seems unlikely that all the rebuilders are reaming the guides undersize so that leaves the possibility that the guide is swelling after a couple of hundred hours or so. All but one of my guides were under the the limit range, and when reamed required the removal of metal not just carbon residue. Anyone else heard about this?

I would consider a "guide tune up" but read the rope trick woes thread first.

Bill

Bronze guides can't actually "swell" but long periods between oil changes can add lead sludge buildup from avgas useage with similar results. Frequent oil changes are always good. Although I have an oil filter, I still change it every 25 hours.

78D has the screen, no filter. Recently went from 25 hour changes to every 20 hours. Have stocked up on a few cases now that Sam's is selling Areoshell again close to home for $20 case. The manual states from 20 to 30 hours depending on conditions. Today's conditions with fuel contents the way they are and it being such a tough world out there these days, 20 hour intervals just seems better!

And buy a gallon of TCP and use it in your avgas!

What's the story on TCP? I've seen Canadian pilots talk about using it but I don't remember anyone I know ever talk about using it. Why is it something to consider?

Rumor has it that loads of Moose droppings are being hauled back from Alaska and boiled into something called Total Carotene Poop on the backside of Mt Nebo.

Hummm, it then appears they are harnessing the methane gas potential of the Moose poop ... my dog makes some pretty large amounts of poop in our yard, maybe I could harness that potential and avoid paying for someone else's poop.

. . . and, avoid the busisness problems that Dave & George have encountered in their venture. Dave's hope of the TCP slowing planes down, and George ever hopeful that something is going to speed his up. Then, they have been bickering over the name of their new company . . .

Speaking of TCP, I've had some on backorder from Spruce for several months now. where do you buy this stuff?

Bruce

Auto gas - 87 oct regular- works well- no sticking valves, no TCP, change oil and filter at 50 hour intervals. Only caveat, don't let it sit in your plane for months at a time. And it's a lot less expensive than avgas.
Rudy

Whenever you think you have water getting to the engine, don't forget to drain the carb bowl. And if you have a electric fuelpump ( 180 Lyc ) drain it too.