Fouled plugs

[Guest Pilot533]

It was a beautiful day for flying, hazy but nice and smooth, I was about to fly on a progress check and we ran up the airplane fine, but I noticed the engine was idling a little rough, so I ran it up again, and waddaya know, the engine ran very rough on the left mag, so we let it run somewhat lean for 1 minute, ran it up and the same thing, then we let it run for 2 minutes and we were able to run it up after that with no problem. I told the instructor I would feel better if we took another airplane that day, do you think I made the right decision, or do you think that we most likely unfouled the plugs and the airplane was ok after the last runup being successful? Anyway, we took the other airplane, and guess what, the same thing, just this time it was the right mag. We ran it for 2 minutes and ran it up, it was ok after that and we completed the flight with no problem. So what do you think? Is it ok to continue the flight if you run the engine for 2 minutes and then the runup is successful?

[Cessnaflyer 56]

That happens quite a bit. If you take a look at an engine that is getting it's plugs replaced you can see all the deposits that can get lodged in there. Usually after you melted or shook the blockage free the engine is safe to run.

[C-JEAN 1]

Hi, Pilot533 and all. It happened twice or 3 times, to me. I was lucky that the first time, I waswith my instructor, so I learned what to do. The one or two other times, I was the PICin a Cessna 172N. When that happens, we push the throttle almostto full, and we lean until it back fires.Don't be affraid ! The engine is made of METALs. With high RPM, high cylinder pressures, andhigh air velocity in the cylinders, it'sNOT long that the plugs ARE cleaned. B-) I have 228 hours of real flights:51 first in Cessna 150, and after that,all in Cessna 172N. How about you ? And also, uncountable hours in Flight SimS.I touched: The FS of the VIC-20 by Commodore C=, FS1, FS2, FS4, FS5.0a, FS6-with-ugly-sound-bug,FS2002 for multi-play, and FS2004 to testmy sceneries. Blus skies.

[Guest Adverse Yawn]

You were probably a bit over cautious. So long as you clear the fouling and can show that there isn't a mag problem, there won't be a problem. One technique you may want to ask your instructor about is to run the aeroplane on the ground with the mixture as lean as you can make it. With ground power settings this will not be an issue and will prevent the occurrence.

[Guest Pilot533]

Alright I thought that I was being to cautious, I didnt feel comfortable flying that airplane at the time, I guess its because I really didnt know much about fouled plugs, now that thats cleared up I'll know what do do next time.

[Guest jrewing]

Mike,Being cautious is not a bad thing. You were right to discuss your concerns with your instructor. If you can, it's a good idea to involve an authorized mechanic in the discussion, too.Here's some information from Lycoming about spark plug fouling. After clicking on the link, search for the title "Spark Plug Fouling" and you'll see some recommended procedures to prevent or reduce lead fouling.http://www.lycoming.textron.com/support/pu...pdfs/SL185B.pdfI wish you continued success in your training,John

[Guest christianholmes]

I was nervous the first time it happened to me too with an instructor- now, I lean the mixture during taxi unless it's really hot out- and by the time you do run-up the plugs will be fine.

[lcseale53 0]

Curious that the Lycoming publication advises against ever using auto fuels in an aircraft engine while telling one how to keep their faltering engine running on avgas.I've been running 87 - 89 grade auto fuel in my continental C85 for twenty years - with the proper STC of course. Cleaning the plugs now occurs on an annual basis rather than monthly. A little Marvel Mystery oil keeps the top lubed in the absence of lead...but the STC does require a tank of avgas every 60 hours.I also have a continental IO520 (no STC available for injected engines) running strictly on avgas. I keep a spare set of plugs that I rotate out every couple of months for cleaning. Generally easing the mixture out a little during run-up will clear the plugs.Regards,Leon