tutuzulu
Joined: 16 Aug 2010
Posts: 1
Location: Charlottesville, VA
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 Posted: Wed Aug 18, 2010 6:11 pm Post subject: ghost in the engine 2200A |
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Hi Listers,
I have an engine problem that has everybody, mechanics, Jabiru personnel, and of course me, totally bamboozled. Any ideas would be welcome.
Here's a review of the problem so far
Immediately after the annual inspection in March, the engine began running rough above about 2,650 rpm. It starts with a little roughness, and the longer it runs above that rpm the rougher it gets, and soon the rpm starts bouncing around wildly within a range of about 2,500 to 2,750. One of the cylinders will start cooling down in EGTs and CHTs. Which cylinder it is will change; it’s nearly always 2 or 4, sometimes 3, and rarely 1. When the power is reduced below about 2,650, the cool cylinder warms up and everything runs smoothly.
It seems like after every change (see below), it runs a little bit better for a little while, but then reverts to the same problem. It’s interesting that I can run it for a while and have the problem be on one cylinder, then shut it down for 5 minutes and then start it again and have the problem be on another cylinder.
The following have resulted in no change:
L, R, or Both magnetos.
Carb heat On or Off.
Electric fuel pump On or Off.
Replaced rotors, distributor cap, spark plug wires, and sparkplugs.
New carburetor. (The only difference this made was that a couple EGTs ran too high.)
Inspections that were normal:
I’ve removed the carb and looked into the intake manifold but could see no obstructions or abnormalities.
There was no metal in the oil filter.
All the valve springs appear to have the same resistance when I push on them. The rocker arms all appear perfectly aligned when in the full up/out position.
I also removed the air intake Scat hose and tried running it with carb intake open to the engine compartment, with both the old and a new carb. No difference.
I'm grounded and heartbroken.
Anybody got any ideas?
Many thanks,
Bob Miller
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Bob Miller |
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