I just went over 10 hrs in my fly-off, so decided to do my first "cross-country" today. Flew to Kingman, AZ and shut down for about 15 min (looking for a diet coke) and the hopped in to return home. I have a Lyc IO-360 and have heard all the stories about hot starts but had no trouble starting mine. It did however seem to be running very rough at or near idle. The run-up and mag check was normal (ran smooth at 1700 rpm). Although a little nervous about the takeoff, all went well and I returned home safely. Once on the ground again the engine idled normally. I assume the roughness had something to do with the engine already being warm/hot. Can anyone tell me if this is normal and what the cause might be?
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Rough Idle
- Thread starter Brambo
- Start date
Guy Prevost
Well Known Member
Loping, rough idle is really common with fuel injected RV's when they're hot. The consensus is that the fuel is vaporizing in the injector lines. Mine does it, and there are a few threads on this forum on the subject. I have better luck if I lean aggressively during taxi and use higher than normal taxi RPM. Since I don't like to ride the brakes, this leads to somewhat faster than normal taxi.
Let us know if you figure out a surefire cure!
Guy
Let us know if you figure out a surefire cure!
Guy
Russ McCutcheon
Well Known Member
This is normal for mine, Bendix injection. It lopes and carries on a bit idling after hot starts but never misses a beat on run up or takeoff and flight. If mine is any indication then your doing fine. Maybe caused from fuel boiling off in the system (vapor lock) don?t know. I have also noted others doing the same thing as they taxi buy after starting hot.
rough idle
I first experienced this when I was going through transition training in my RV8 with Dave Austin. Dave is a great instructor, hailing from Denton, TX. Right after start, the engine (IO-360-B1B) began to run rough. Dave had me start the boost pump and the problem immediately ceased! Dave explained that the higher pressure of the electric boost pump collapses the vaper lock in the injector lines. Seems reasonable to me!
Craig
PS: I would recommend Dave for RV transition. I have rudder, throttle and prop controls in the back seat, which Dave required for training in my own aircraft. What a treat to train in the aircraft that I will be flying!
CT
I first experienced this when I was going through transition training in my RV8 with Dave Austin. Dave is a great instructor, hailing from Denton, TX. Right after start, the engine (IO-360-B1B) began to run rough. Dave had me start the boost pump and the problem immediately ceased! Dave explained that the higher pressure of the electric boost pump collapses the vaper lock in the injector lines. Seems reasonable to me!
Craig
PS: I would recommend Dave for RV transition. I have rudder, throttle and prop controls in the back seat, which Dave required for training in my own aircraft. What a treat to train in the aircraft that I will be flying!
CT
What a coincidence
My RV-4 ran absolutely awful on the ground in Kingman AZ. It actually quit while I was taxing in. Maybe there is some kind of magnetic distrubance there that interfers with the gasoline atoms and ...I hope you aren't buying this. Funny though mine did run very rough there.
My RV-4 ran absolutely awful on the ground in Kingman AZ. It actually quit while I was taxing in. Maybe there is some kind of magnetic distrubance there that interfers with the gasoline atoms and ...I hope you aren't buying this. Funny though mine did run very rough there.
smithhb
Well Known Member
Bill, I am at the 25hr point in my Phase 1 and I have an IO-360 as well. I also see the loping after the engine is warm and have been told by a couple of different A&P's that adjusting the idle mixture will help. The also advised that this is normal for a new-run engine and the idle mixture will help at lower fuel flow.
They also advised, as others have already mentioned, to lean somewhat at idle until you sense the engine run more smoothly.
HTH
John Clark
Well Known Member
Rough idle
The boost pump is a non-issue in the case of an injected engine. The theory on this rough idle issue is a slight vapor lock in the fuel lines from the "spider" (flow divider) on top of the engine to the injectors. Problem is, the boost pump will not raise the pressure on that side of the servo. If it did, the engine would go ugly-rich anytime the boost pump was turned on. The good news is that at higher RPM, like at run-up, the fuel flow and cooling air both increase and the problem goes away.
John Clark
RV8 N18U "Sunshine"
KSBA
The boost pump is a non-issue in the case of an injected engine. The theory on this rough idle issue is a slight vapor lock in the fuel lines from the "spider" (flow divider) on top of the engine to the injectors. Problem is, the boost pump will not raise the pressure on that side of the servo. If it did, the engine would go ugly-rich anytime the boost pump was turned on. The good news is that at higher RPM, like at run-up, the fuel flow and cooling air both increase and the problem goes away.
John Clark
RV8 N18U "Sunshine"
KSBA
