IO470 Idle Help

[flyby]

This is obviously not SuperCub. But it is a Peterson 260SE, is that backcountry enough? Can delete if not appropriate.

Next to the cub, our family hauler is the 182 with an IO470. I value the knowledge on this forum so I thought I'd ask:


Our 182P has an IO470 (Peterson 260 STC). Having a heck of a time keeping it idling.

When cool/cold engine the boost pump has to be on low in order to keep at idle or it will die, like fuel starvation. When engine is warm it will idle fine without the use of low boost. I noticed today after some time warming up, it would idle without boost pump on, however when advancing past 1000 rpms it would then studder, needed boost pump again until it was past 1200 rpm. After the flight and while at full operating temps, I could run at all rpm range without boost pump. It seems this issue is consistently getting worse over time.

Mechanical fuel pump has been rebuilt I believe, but I would have to confirm on the logs. Looking for ideas or direction, last few annuals the mechanics cannot seem to nail down what the issue could be. Adjusted idle mixture etc... At times the fuel pressure gauge will fluctuate in cruise. All are very inconsistent but becoming more frequent.

I am doing a ground run today and will see if I can record some pressure readings on the gauge and report. Any other ideas? One person suggested it could be debris in the mechanical pump relief valve.



Sent from my iPad using Tapatalk

 

[stewartb]

http://www.airplains.com/images/support/Service Bulletins/Air Plains Cessna 182/SID97-3F.pdf

 

[OLDCROWE]

I had the same situation (IO520) and found a vacuum leak (from when I had the instrument and standby vacuum system removed) was causing it.

 

[mike mcs repair]

I had the same situation (IO520) and found a vacuum leak (from when I had the instrument and standby vacuum system removed) was causing it.

good point,

I'm not familiar with that STC, but in general....

some leaks to check for:

• loose or missing intake bolts to cylinder
• loose or missing hose clamps on intake rubbers
• partially missing intake gaskets
• intake hoses slipped off one side
• intake tubes cracked at weld & up by cylinder (if welded style)
• intake "Y" sagged down(depending on which style)
• hole worn in front crossover, or cracked
• worn bushings/shaft at throttle butterfly

i'm sure their are more...

then as Stewart pointed out, rechecking both low and high fuel pressures, then readjust idle mixture adjustment till you get a little black smoke at a low idle of like 350 or 400(if you can get it that low, will require good camshaft lobes)

 

[Dave Calkins]

good point,

I'm not familiar with that STC, but in general....

some leaks to check for:

• loose or missing intake bolts to cylinder
• loose or missing hose clamps on intake rubbers
• partially missing intake gaskets
• intake hoses slipped off one side
• intake tubes cracked at weld & up by cylinder (if welded style)
• intake "Y" sagged down(depending on which style)
• hole worn in front crossover, or cracked
• worn bushings/shaft at throttle butterfly

i'm sure their are more...

then as Stewart pointed out, rechecking both low and high fuel pressures, then readjust idle mixture adjustment till you get a little black smoke at a low idle of like 350 or 400(if you can get it that low, will require good camshaft lobes)

In other words......an induction leak leading to a lean condition at idle or low rpm seems likely.

Please let us know whta you find on this issue, FLYBY. Thanks

 

[flyby]

Flew it today. Seems odd that it just isn't consistent. It wasn't as big of issue today. After it's at full operating temp the issue goes away. I'll start tracking down these trails and will try to report back. Last annual the A&Ps did check/adjust fuel idle mixture but not sure how deep they got in to the pressures or looking for a vacuum leak.


Sent from my iPad using Tapatalk

 

[mike mcs repair]

... After it's at full operating temp the issue goes away. ...
Sent from my iPad using Tapatalk

cracked cylinder head???

did they do the pressurized cylinder and soapy water in between fins check?

 

[Tom3holer]

I would first check the RPM rise at idle. It should be 25-50. If there is none it just dies as you lean to cutoff at idle you need to adjust the idle mixture linkage per the stewarb made.

 

[flyby]

I would first check the RPM rise at idle. It should be 25-50. If there is none it just dies as you lean to cutoff at idle you need to adjust the idle mixture linkage per the stewarb made.

Are you referring to the rise while cutting the mixture shutting down at idle? If so then yes it does get an RPM rise, about that amount while going mixture cutoff.


Sent from my iPad using Tapatalk

 

[flyby]

cracked cylinder head???

did they do the pressurized cylinder and soapy water in between fins check?

I'll have to ask about that - I will be with a mechanic tomorrow at an EAA meeting - will come to him with these lists you suggested and see what he thinks.


Sent from my iPad using Tapatalk

 

[Tom3holer]

Should be 25-50 RPM. As long as there is a noticeable rise your in the ballpark.

 

[mike mcs repair]

Should be 25-50 RPM. As long as there is a noticeable rise your in the ballpark.

AT the SPECIFIED RPM ONLY, is that a valid test...

 

[skywagon8a]

If you have an all cylinder EGT/CHT instrument, does one cylinder have drastically different temperatures than the others while the rough running is happening? If so, start your search there. You could have a dirty fuel injection nozzle.

 

[flyby]

Unfortunately no on the all cylinder EGT/CHT. Talked with A&P and he is going to look over induction system, he is pretty certain in his opinion it is related to the flow divider. Taking up to him in a couple weeks and will report if that was the case or not.


Sent from my iPad using Tapatalk

 

[skywagon8a]

Get a half a dozen small (baby food sized) jars. Remove fuel nozzles, with them connected to their fuel lines run the fuel pump with the mixture full rich for a short time. Do the jars fill the same amount? If one is noticeably less, that one has a dirty or restricted nozzle. It could also be a piece of something in the flow divider blocking that line.

 

[n40ff]

Soak nozzle in Hoppies No. 9

Makes it shoot straight

 

[OLDCROWE]

Soak nozzle in Hoppies No. 9

Makes it shoot straight

Every 250 hours weather they need it or not, works wonders especially in a heated ultrasonic cleaner!