Low Oil Pressure Running Rough

[Cwalsh7997]

Hey guys my plane came out of annual about a month ago, ever since then I noticed that when I fly if the oil gets to under 6 quarts when I decend to the airport after flying as soon as I get to the airport and am about to land, I notice the oil pressure will drop to about 50 which is still within means and my engine starts shaking and not producing full power?? Please help

[Yetti]

Bad valves/cylinder.  When cold and after a switch/mag check to make sure your mags are grounded, pull the prop through by hand.  See if one cylinder is easier to pull though.

Edited July 6, 2016 by Yetti

[cnoe]

What engine? The minimum safe oil level for an O/IO-360 is 2 qts. so I doubt that your oil level has anything to do with it.

First thing I'd do is an in-flight mag check.

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[Bob_Belville]

3 minutes ago, cnoe said:

 

What engine?

An F model is probably the IO360-A1A.

[cnoe]

Do you have an engine monitor? Descent leans the engine; were there any fuel injection adjustments? Maybe a partially plugged injector? A monitor would readily show the cylinder flame out.

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[N201MKTurbo]

So, the question is, does the oil pressure drop and the rough running have anything to do with each other? Usually not. Have you played with your mixture when it gets rough to see how that affects the roughness?

[Cwalsh7997]

It's the strangest thing, I know it shouldn't be related to the oil level 

[PMcClure]

Low rpm?

[Cwalsh7997]

Full rpm, low altitude, mixture rich, oil temp is good and chts are good

[carusoam]

(1) Engine Shaking after annual?

CW,

you have some spelling and word choices that make this thread a challenge to understand.

I simplified it to four words.

If those four words are true, it may be time for a wellness visit to the mechanic...

(2) 'not producing full power' is another sign something isn't right.

(3) not posting a JPI graph or associated numbers is a sign that there isn't a complete story that other people could help you with.

 

I see three reasons to see a mechanic without the need to go fly it.  It may be as simple as a loose ignition wire or as important as a broken engine mount...

Let me know if I missed something?

Best regards,

-a-

[Marauder]

I would do a compression test or at least as suggested above by my esteemed colleague and fellow F owner, Yetti, pull the prop through by hand. My guess is you have some sort of ring problem and are burning the oil. It would explain the roughness and the lower oil level.

Also put your finger in the exhaust while it is cool and see what the soot looks like. Should be gray and sooty, not black and sticky.

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[cnoe]

1 hour ago, Marauder said:

I would do a compression test or at least as suggested above by my esteemed colleague and fellow F owner, Yetti, pull the prop through by hand. My guess is you have some sort of ring problem and are burning the oil. It would explain the roughness and the lower oil level.

Also put your finger in the exhaust while it is cool and see what the soot looks like. Should be gray and sooty, not black and sticky.

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Now I'm thoroughly confused. With all due respect when did we start talking about burning oil?

It's all so confusing. When rpm's drop the oil pressure drops, but the OP said that he's making full rpm. I can tell you one thing and that is if I'm flying along at full rpm and my oil pressure drops significantly I'm putting down at the nearest airport using reduced power.

Also, OP says his oil temp and cht(s) are good. Does this mean you have an engine monitor (multiple cht's)? If so, what are the EGT's doing; that will tell you a lot.

[Marauder]

57 minutes ago, cnoe said:

Now I'm thoroughly confused. With all due respect when did we start talking about burning oil?

It's all so confusing. When rpm's drop the oil pressure drops, but the OP said that he's making full rpm. I can tell you one thing and that is if I'm flying along at full rpm and my oil pressure drops significantly I'm putting down at the nearest airport using reduced power.

Also, OP says his oil temp and cht(s) are good. Does this mean you have an engine monitor (multiple cht's)? If so, what are the EGT's doing; that will tell you a lot.

I read his message too quickly. I missed the "if" in his sentence. It sounded like when he lands he finds the oil below 6 quarts and notices the problem. 

I hope he has an engine analyzer because the pieces of this puzzle aren't fitting together right.

[ArtVandelay]

At full idle my OP drops to 55, JPI flashes, after landing when I'm back to 1000rpm oil pressure returns to normal.

I doubt that's the problem.

[Cwalsh7997]

When the problem starts to occur right on final every time it does, I make sure my rpm is full, but if I try to give it power the plane starts to shake and won't give me full power, and I do not have an engine monitor

[carusoam]

Does your mind come up with questions like...

1) What will I do if you hear the stall horn and need to go around?

2) what are my choices going to be?

3) why don't I take this to the mechanic when seven other people don't find this to be normal engine behavior.

4) why is my engine not talking directly to me instead of my friends on MS..?

 

Something is unusual, you may want somebody to look into that...  It's worth talking to your mechanic regarding your observations.  It is possible that he adjusted something at annual that is showing up under idle conditions on warm days...  Is the engine still running?  Or is it just turning in the wind?  (My C did this, got its idle adjusted)

Best regards,

-a-

[N201MKTurbo]

If you try to give it power on final and it balks, will it eventually give you power? You may just have your idle mixture mal adjusted.

[cnoe]

I'm starting to understand. Prop "control" is full forward but the "rpm" is reduced? In that case lower oil pressure is normal. It sounds like a mixture issue to me as well. Still just a guess.

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[Browncbr1]

It could be that your oil fouling plugs at idle. Post photos of plugs and clean out any lead and check resistance.     I do not go full rich unless I'm going around..  There are other who do this too, but I'm not making any suggestions on how to operate.  However, full rich is known to foul plugs on some engines. 

 

Also, verify your mechanic didn't change the timing from its configuration when you bought the plane.  I think you recently bought that F, right?   Mine was a similar situation after first annual.  Engine had been running 25 BTDC when I bought it and at first annual, the mechanic set according to the data plate, which is 20btdc if the case was overhauled after 1992 or so.  some owners and mechanics "were not aware that the data plate was changed to 20" by default.   20 degrees gives you a crappy running engine and it took me a few months to figure out what had happened and that the timing was to blame.  Not a single problem since going to 25, so atleast try to verify your timing.   Plugs and timing are things you can pretty easily check yourself at no cost before starting to involve mechanics.  Jmho

Edited July 6, 2016 by Browncbr1

[Yetti]

I am going to rewrite your issue and then we will have another go at it.

 

On final PROP control is full forward.  Mixture control is full forward.  You are at sea level, but altitude density is about 1000-2000 depending on the heat.

You advance the throttle and the engine runs crappy.

Did not notice this prior to annual or the days getting hotter.

I would still do the poor man's compression check.

It sounds like your mixture might be off.

Please confirm the above scenario.

 

Edited July 6, 2016 by Yetti

[jclemens]

I spoke with the OP today regarding the issue he is having.  I figured I would post here to shed a little light on things.  My shop did the annual on his aircraft.  During that annual a LOT of issues were dealt with that he inherited when he bought the plane.  Prior to annual, the plane was not developing full MAP due to a collapsed intake coupler and a leaking induction tube.  Nor was it being operated at the proper RPM due to a grossly inaccurate tach and a defective prop governor.  Along with correcting these issues, the front cowling was modified with the LASAR closure.  This plane is not equipped with an engine monitor, so it's a little more difficult to troubleshoot.  I think the oil pressure difference he is used to seeing vs. what it is now is caused by the fact that the engine now makes rated power and is being operated harder.  The pressure is well within limits, I don't see any correlation with that and any engine roughness.  I suspect an exhaust valve sticking at low power after cruise.  He is bring the plane to me tomorrow for us to look at.  We looked at the plane for the same issue about a week or so ago briefly.  Compressions are all fine, plugs and injectors rechecked as well as timing.  All good there.  This time he is leaving the plane so we have more time to investigate.  I will post back once we determine the issue.  

[cnoe]

Glad to hear someone other than an "internet mechanic" (like myself) is giving it a good going over. There's been way too many loss-of-power-in-the-terminal-area incidents already.

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[ArtVandelay]

To me an engine monitor is a must have, OP should be that at the top of the list.

[jclemens]

An engine monitor is definitely helpful, no doubt. I could most likely figure this out from a JPI download, certainly narrow it down to one cylinder. I have communicated the benefits of an engine monitor, maybe in the future  he will install one. 

[carusoam]

+1 for engine monitors.

Three manufacturers of the devices have done a great job of improving the breed of devices.  A wave of upgrades has occurred over the last ten years.

Used JPI units are available.  There is a reputable guy here that sells them. 

Can't get economically much better than that.  Unless you can work with the installer.  You do the work, he does the signatures...

Best regards,

-a-