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Date: Mon, 23 Jun 2014 19:27:41 -0400
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Subject: Rough idle in Lancair 360
From: Kevin <cloudsurfer835@gmail.com>
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Hello fellow Lacairians,

I've been dealing with a rough idle problem on a Lycoming IO-360-B1B in a La=
ncair 360 for way too long. It only happens when the engine is hot, so I'm w=
ondering if anyone else has had this problem and what, if anything, can be d=
one about it.  The engine runs very strong in flight, and the problem only o=
ccurs on the ground when hot and at low RPM.  Turning on the boost pump has n=
o effect. The previous owner said he had the same problem so this has been g=
oing on for a very long time.=20

After having 4 mechanics look into it and spending thousands of dollars, the=
 problem remains. So far, we have put on a new fuel servo, new injectors, ne=
w plugs, and checked the timing and ignition system and found no problems. I=
've also subscribed to Savvy Analysts and they can't find anything wrong in t=
he engine data. The next couple of things we are going to look at (again, bu=
t more thoroughly) are both fuel pumps (mechanical and electrical), and the f=
uel flow divider. We are also thinking that there might be an air leak somew=
here in the fuel system because the boost pump won't prime until the engine i=
s cranked on the first start of the day, but then it boosts just fine.  We a=
re also thinking that we could have a vapor lock problem since it only happe=
ns when hot, and these are obviously tightly-cowled engines. I've heard from=
 other Lancair 360 owners that many of these planes tend to idle rough when t=
hey're hot, so perhaps we've been chasing our tails this whole time and this=
 is something we just need to live with?

One last anomaly that might be worth noting since it has now happened twice.=
 During climb out on two hot days, fuel pressure began fluctuating (+/- 5 ps=
i), but then stabilized in level flight at higher airspeeds. Once again, tur=
ning on the boost pump had no effect. Perhaps another indicator of a possibl=
e vapor lock issue? =20

Any advice would be greatly appreciated!

Thanks,
Kevin