Matt
Since the missing problem is altitude related, I would pull the air box away
---From the rear of the carb's. Reach inside the carb and see if the sliding
barrel is stuck. It should move freely up or down, if the barrel is stuck, or
moves very slowly. it needs to be cleaned so that it will move freely. (This
sets the mixture as the airplane climbs to altitude), hence the rough at
running at altitude, and the smooth running at a lower altitude. This is why
at altitude the EGT is going up (lean mixture).
If the barrel is not the case. pull the carb and clean out the float chamber
and jets. Something is partial blocking the main jet.
Carb ice is not a problem with the 914. The turbo raises the air temperature
above temp for ice formation.
Jim Brown
N398JB
N112B (RV 7A almost ready to fly)
Matthew Carpenter wrote:
>
> A weird problem with our 914 showed up on the way home from Oshkosh last
> Wednesday.
>
> 1.5 hours from Oshkosh heading to Texas, the altitude was 6500 msl and
> the OAT was 44F.
> The engine begin to lose power, the sound changed. The EGT, normally at
> 1360 was at 1550 and going up.
> When the EGT hit 1600 the engine begin to sound ruff, like it was
> starting to miss, but not to the point of stopping.
> To us it seemed the the mixture was to lean.. might we be seeing some
> carb ice? Water in the gas?
> I turned on the secondary full pump, the EGT dropped down to 1550, and
> the engine did smooth out, but the power was
> still not there. The MP showed 31, RMP was at 5000, it all looked
> good.. except for the EGT.
>
> We landed and replaced the full filter.. maybe it was starting to clog up..
> Ran fine for 1 more hour, 4500msl and 65F OAT, then the problem came
> back. I went down to 2000 msl, and the problem went
> away.
>
> We landed once more, and I checked all the hoses, and electrical wiring
> under the hood, everything looked fine.
>
> We ended up flying the rest of the way at 3500msl, and had no problems
> for 3 hours..
>
> Any ideas?? Why would the EGT drop when I turn on both fuel pumps, and
> then return to 1600+ with only 1 pump on. (even toggled the two pumps).
>
> Hope someone had some ideas, I would like to fix it before the next long
> flight.
>
> Thanks,
>
> Matt Carpenter
> A138
> N138WJ
> Amarillo Texas
>
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