Rough run up

[bonal]

let me set the stage. Two weeks ago we flew home from Groveland and departed in very very smoky air there was lots of ash all over the ground as well. The flight home was perfectly normal all indications fine. After landing I noticed the idle was a bit lopey and did a run up on the taxi way which was fine cycled the mags and rpm drop was normal and the engine was smooth but idle was still lopey. I thought perhaps the air filter might have gotten clogged up from the smoke and ash. So before today's flight I installed a new one the old one was very dirty and only a few months old. When starting it fired right up although it seemed to hit hard when it did. Still had that lopey idle when doing the run up it vibrated real bad and I could not even reach my run up speed cycled the mags and both were firing and they grounded when I shut the off. Tried to work the mixture to see if perhaps a plug was fouled but that did not help. Engine gauges and fuel pressure normal. After shut down I pulled the prop through and felt good compression on all cylinders. I also had a couple back fires when I was trying to run it up.

I was really looking forward to getting out for a flight as this was first opportunity since the big valley fire which has caused so much distruction so close to home and caused so much stress responding to the damage. On the bright side it happened at home not some distant location. Will be taking it over to LASAR next week to see what's up.

any thoughts would be appreciated 

[jetdriven]

Sounds like a magneto worked loose or jumped time. The last one I saw like that would not start without lots of cranking and would backfire when trying to start.  The mag drop was 200 on the right msg. It was timed 20 degrees after TDC.  Fresh pre buy with sale. 

Edited September 27, 2015 by jetdriven

[Hank]

Sounds like my recent problems. Reset timing, worked well for a brief while. Then bad idle, L mag drop ~200 at runup; I tried to burn off the plugs and it coughed, spit and had small backfires so I backed off and put her away. Next step was clean and check all plugs and harness, all good. Then pulled L mag and sent to Kelly. Reinstalled, retimed, ran beautiful on L mag and bad on right.

Pulled all plugs again, retested, put 'em back in, R mag good, L mag 200 rpm drop! Replaced all plugs, no problems since. Now I have eight plugs in the hangar, of which seven are good, but neither I nor the FBO have a bomb tester to check them and find the bad one.

good luck solving your problems. I would start with the plugs. As I found out, resistance checking plugs and continuity testing in the harness isn't enough, you need a bomb tester for the plugs. If that doesn't fix it, you're looking at a magneto issue. OH runs about $500 each . . .

[bonal]

So just back from LASAR found both number 1 plugs gas soaked. We put them on the tester and neither one would spark. Other 6 were firing normal. There was nothing like carbon or lead fowling visible. We cleaned them both up and they both fired in the tester. Did a compression check and number 1 was at 78 others all in high 70's did an oil change as I was around 20 hours and it was opened up anyway. No visible sign of any anomaly on the inspection. Run up was back to normal and short test flight was without issue. The plugs are Tempest and just over 100 hours old. Can't figure what would cause then to both drop off after a flight with no issues. I wonder if the dirty air filter from all the smoke and ash could have caused a over rich condition after landing. When I replaced it last week there was quite a bit of sooty coating on the external side. Well I guess it's a mystery glad there was nothing broken.

on a side note got to spend time with an Ovation 2 a TKS ? And a Bravo that were in for service.

[Mooneymite]

That's good news.  I'm happy it was just plugs.

The gas soaked plugs are "interesting", but fairly easy to keep an eye on.  I suspect the reason they were gas soaked was because they weren't firing, but what caused them to stop firing in the first place is the head-scratcher.

I presume you tried the high-power-lean run-up and that didn't clear the problem?

[midlifeflyer]

That's good news.  I'm happy it was just plugs.

The gas soaked plugs are "interesting", but fairly easy to keep an eye on.  I suspect the reason they were gas soaked was because they weren't firing, but what caused them to stop firing in the first place is the head-scratcher.

I presume you tried the high-power-lean run-up and that didn't clear the problem?

That was my first thought when I read the OP. The related one, Bonal, is whether you regularly lean for taxi after you start, and again after clearing the runway. Good operating practice in any make model. I remember flying with a guy in his 182 out of Los Angeles and he aggressively leaned for taxi. When I commented on it he told me he was the only 182 pilot he knew in the area who had never had fouled plugs.

Edited October 1, 2015 by midlifeflyer

[bonal]

Yes I always lean aggressively while on the ground but not until wheels are planted could have been too rich on short but I know it was not full rich and yes I tried to do the run up last week but it was shaking so bad I did not want to cause damage as I did not know what the problem was. this morning I could barely make enough power to taxi. Weird 

[Marauder]

That was my first thought when I read the OP. The related one, Bonal, is whether you regularly lean for taxi after you start, and again after clearing the runway. Good operating practice in any make model. I remember flying with a guy in his 182 out of Los Angeles and he aggressively leaned for taxi. When I commented on it he told me he was the only 182 pilot he knew in the area who had never had fouled plugs.

During my first year of ownership, I was not very aggressive on leaning. Ok, I never leaned and I found that I was fouling plugs. Since then, I lean as aggressively as I can and haven't had a fouling problem.

Sent from my iPad using Tapatalk

[Mooneymite]

but it was shaking so bad I did not want to cause damage.

Yep...a fouled plug (or, in your case, two) can really make the plane shake, but the high power, lean run-up can clear the rough running engine like a charm.  There will be no question as to when the plugs are firing again.

This is a technique item and there are different ways to do it, so look around on the Internet and find what works for you.

[N201MKTurbo]

Maybe the plugs have too low a resistance? Get some good Champions!

[bonal]

Yes I definitely know how to do a high power lean out to clean the plugs but when I tried this last week I could not even get it to pull past 1500rpm and it shook so violently I thought better not push it could break something else.

[N201MKTurbo]

I had the same crap recently. rebuilt the mag, replaced the harness, then replaced all the sparkplugs after swapping them every which way.

After all that it finally ran right.

I think it was the plugs...

I'm now running a set of AC260s 40 year old NOS three electrode massives. They are still on the approved list for the engine. It runs great! 

[yvesg]

Yes I definitely know how to do a high power lean out to clean the plugs but when I tried this last week I could not even get it to pull past 1500rpm and it shook so violently I thought better not push it could break something else.

What is the correct procedure to clean fooled plugs on our Mooneys? When I need to do it, I never remember what it is.

Yves

[Mooneymite]

Yes I definitely know how to do a high power lean out to clean the plugs but when I tried this last week I could not even get it to pull past 1500rpm and it shook so violently I thought better not push it could break something else.

Wise choice.

 

[DXB]

What is the correct procedure to clean fooled plugs on our Mooneys? When I need to do it, I never remember what it is.

Yves

Yup I had the same problem- then accumulated protocols from various sources including this site and made a detailed card to keep in the plane - there seem to be multiple valid techniques.  It's been much less of a problem since I started leaning aggressively for taxi.  

I'd best let the real experts on here answer your actual question though...

[ryoder]

Fine wires and super aggressive leaning on the ground and mild leaning in the pattern all the way to short final worked great for me.  I had terrible mag drops at first and thought I needed a new mag.  Once I installed brand new fine wires it ran immediately like a brand new engine.  One of my plugs gets oil fouled and my mechanic sand blasts it after spark testing it and I am back in business.  

[bonal]

What is the correct procedure to clean fooled plugs on our Mooneys? When I need to do it, I never remember what it is.

Yves

it seems the Champions were much easier to fool, a simple slight of hand would do the trick and they would be so confused I could almost never get them to clear up. However the Tempest are a much wiser more knowledgeable plug and not so easily fooled. Problem here was that since there was no spark on both plugs there was no fire in the cylinder so nothing there to burn off the fowling like when only one plug isn't fireing I doubt I'll ever know why they both quit like that

couldnt resist your little typo. 

[jetdriven]

Fine wires and super aggressive leaning on the ground and mild leaning in the pattern all the way to short final worked great for me.  I had terrible mag drops at first and thought I needed a new mag.  Once I installed brand new fine wires it ran immediately like a brand new engine.  One of my plugs gets oil fouled and my mechanic sand blasts it after spark testing it and I am back in business.  

don't sand blast fine wire plugs. It strips the thin iridium coating off the ground strap and ruins the plug. 

Edited October 2, 2015 by jetdriven

[Mooneymite]

don't sand blast fine wire plugs. It strips the thin iridium coating off the ground strap and ruins the plug. 

This is what I've understood, but I can't  find an authoritative source.

I pick the lead out, but there really isn't  a reason to sand blast.  Perhaps a softer blassting media (walnut shell) could be used?

[N201MKTurbo]

I've been cleaning fine wires with glass beads for years without any ill effects. Normal usage causes them to erode somewhat. If they didn't erode they would last forever. My last set I got about 800 hours out of and they were glass bead blasted about 16 times.

[Mooneymite]

Here's  what Tempest says:

 

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.tempestplus.com/Portals/0/PDFs/Sparkplug%20Cleaning%20The%20Right%20Way%20061212.pdf&ved=0CCEQFjAAahUKEwjO5s-L4aPIAhXIaT4KHVKYDPo&usg=AFQjCNE1omaG6CgnMTZejzps4zLkBiijcQ&sig2=XaQA9AFix7i8CsRRegqzrQ

[N201MKTurbo]

Interesting, I inspect them with a high power magnifier and I've never seen that effect. Some times they will build up like that, but some additional cleaning will usually get them out. I don't clean them aggressively with the glass beads, I scrape the deposits off with a vibrator bit in a handheld pin vise.,I find that more effective then using the vibrator. Then I give them a short blast with glass beads to clean everything up. I use an ancient Champion plug cleaner and bomb tester. 

Not what jet driven was talking about. 

I have my last set of plugs, I will take them to work and look at them under a microscope and let you know what I see.

[yvesg]

it seems the Champions were much easier to fool, a simple slight of hand would do the trick and they would be so confused I could almost never get them to clear up. However the Tempest are a much wiser more knowledgeable plug and not so easily fooled. Problem here was that since there was no spark on both plugs there was no fire in the cylinder so nothing there to burn off the fowling like when only one plug isn't fireing I doubt I'll ever know why they both quit like that

couldnt resist your little typo. 

OK bonal. The Frenchman in me got fooled by your response. How do we clear fouled plugs before takeoff?

 

Yves

[bonal]

OK bonal. The Frenchman in me got fooled by your response. How do we clear fouled plugs before takeoff?

 

Yves

There are many here much more qualified than myself to answer that question. I know what works for me perhaps others will chime in and then we can both learn what is the correct procedure. I like to listen before I speak. Others, you have had plenty of time to warm up to the question on the table.

[Hank]

Plugs fouled with oil have to be removed. 

Plead fouling can be cleared at the hold short line during runup. My runup,is 1700 and Full Rich. Rough mag drops are often fouled plugs, so I advance to 2000 and lean some, watching EGT. I keep it 100-150° Rich of Peak, which usually means lean until EGT rises at least 100°. I hold it there for 60 seconds by my yoke clock, back to Full Rich, back to 1700 and check the mags again.

when I recently had mag trouble, with ~200 RPM drop on the Left mag and 75 on the right; I tried to burn off the plugs as above, but at 2000 RPM she was shaking, spitting and coughing, so I taxied slowly back to the hangar.

fouling can be greatly reduced by leaning a lot while on the ground. I generally pull the mixture lever ~3/4 to Idle Cutoff; once I parked on the grass, and on departure I had to give it more power to get back onto the asphalt taxiway, and the engine almost died from being too lean. Pushed the mixture forward some, smoothed out, pulled onto the asphalt, reduced throttle and leaned back out. This will keep you from accidentally taking off too lean, as the engine won't run with more throttle.