Lycoming 0-290 sputter

[MikeLima]

The mechanic is tied up till next week so I thought I'd check here just to see if there's any consensus of what the issue might be. And, yes, I know that a real diagnosis will still be necessary.

Motor runs fine under power. No problem starting. When power is pulled out while flying the motor will spit or pop (not a backfire pop, more of an abbreviated sputter). It will continue to do it sporadically so long as the power is pulled. Immediately stops when power is reapplied. On the ground will do it a little but not nearly as often... Idles well.

Anyone have any helpful ideas about what may be the issue?

ML

 

[FORANE]

look up afterfire.

 

[MikeLima]

I just did. Very informative. Thank you.

 

[Dan Thomas]

When reducing power, the mixture gets quite lean during the deceleration. A weak spark will often not fire a weak mixture. Therefore, I'd suspect some bad plugs or, more likely, the mags need work.