Engine rough (miss shots) when idle in flight

[Camillo]

Hallo.

I have done a few hours of flight on my -4. It has a new Lycoming injected experimental IO-320. It has a Christen oil system.

During last months, a couple of times it runned rough after having idled preparing for landing (I have to idle way before landing in order to lose speed and height). One on ground, I pulled the mixture between half and 3/4 cut and the throttle all in to clean the spark plugs. The further flight went OK.

Yesterday during both landings engine went so rough that I had to abort the first landing fearing of an engine failure. Even increasing power gently didn't stop the faltering. Nearly the same on the homing landing, where I had to slip and lose height in order to land safely without going around.

I have to admit that during the last flights I use to power on the aux boost pump. I now suspect that the boost pump induce for flooded engine during low power settings. Actually, during the first landing I immediately shut off the pump and while for the next seconds the engine continued to miss shots, during the second approach, which became an actual landing, engine run OK (or at least I can't remember it run badly). I will for sure avoid powering on the boost pump in the future. While on ground, idle is wuperOK. Issues only when flying idle.

I was wondering is this can be a reasonable reason for the issue or if I have to investigate more. Actually, I can't trust on the engine and this makes me very upset.

Thanks.
Camillo

[rv8ch]

Ciao Camillo, what kind of fuel injection do you have? Also, what kind of air filter system? Are you running regular magnetos, or electronic ignition?

How does it behave when flying? Do you have an engine monitor? If so, you can upload data to savvyaviation.com and get some interesting insights.

[Camillo]

Ciao.
I have regular magnetos. Fuel pump and air filter system from Van's.
When flying is OK (apart when idling). On ground, idle ot WOT, is OK.
I do have Dynon Skyview EFIS and EMS. How can I download data from it?
Thanks.
Camillo

[sailvi767]

If you have the continental style injection system that ECI was selling its designed not to use the boost pump unless the primary pump fails. If you turn it on you will get a rough running engine. If it’s a more standard lycoming system then you have a issue and the pump should be on for takeoff and landing.
G

[Walt]

Idle mixture set correctly??
On a Bendix/Silverhawk FI system (std on Lyc) the boost pump should have no effect on how the engine runs unless the pressure is over 45 psi.

[Camillo]

I have an airflowperformance aux pump. The filter is just after the pump.

Engine is a Lycoming EAIO-320 D1A part number YENPL-RT10467. As indicated in the Lyco major part sheet, engine injector is AVX-5VA1 from AVSTAR.

I bought the engine brand new (experimental) from Van's in 2014. In the engine log test sheet is hand written: "inhector aux-5VA2 S/N AV027282 assigned to this ENG". In the engine test verification there are some values below minimun requirements, if that may help.

As of idling mixture, no, I didn't. I will check how to do it. However, on the ground minimum works perfectly. Fuel pressure is around 30/32 PSI (not looked during rough engine operations).

Thanks.
Camillo

[Carl Froehlich]

Assuming you set your idle mixture correctly (I find most new engines are way rich) then I suggest you look for an air leak.

I experienced the same condition way back in my learning days. The engine ran fine when at power, but pulling back to idle it was scary rough. I ended up doing a dead stick landing as I figured that was safer than trying to nurse it in.
The cause was one intake manifold being loose (one of the two bolts missing on this rented plane). The manifold was close enough to reseat under full power, but dropped away at idle.

Your may have a harder to find air leak.

Carl

[lr172]

I would start with Idle mixture. They are often very far off (overly rich) when they come from the factory. It should be adjusted before first flight. Probably too rich. Runs ok cold, as cold engine needs/likes richer mixture, but chokes on the extra fuel when hot and wants a leaner mixture.

Larry

[Lenny Iszak]

Check for an intake leak. Intake gaskets, rubber couplings, check valve on the bottom of the sump or the MAP sensor hose.

If you do have an intake leak you can see it on your EGTs rising quickly when you pull the throttle back. They should not do that. Would be happy to look at your engine monitoring data. Best is to upload the log files to https://www.savvyaviation.com/ and share a link to it, but you can just send me the raw log files too. Good to keep an eye on engine monitoring data for the first few hours. There are a lot of things you won't catch on the screen while flying.

Lenny

[blaplante]

This should help you with the data pull from the Dynon: https://forum.flydynon.com/threads/ems-data-log.12352/