>I have a very minor surge (occasional) on full power & RPM's. At 25
>square the engine runs flawlessly. My Sierra has an IO360A1B 200 hp
>fuel injected engien. My A&P said it is probably a Mag Coil, unless he
>sees an obvious crack its $200 each, or he can remove the injectors and
>flush them.
>Are there any approved fuel additives that can be added to clean them?
>I go for annual in 2 weeks and I can get them pulled at that time.

None that I know of. Pull them at annual and do the "piss test" to see
that they all fill the bottles at the same rate, and that they have a
smooth, straight stream with no "feather" or spray. If so, then no
"cleaning" is needed. If they do need cleaning, you can not stick anything
into the nozzle to clear trash, it will score the nozzle and affect the
flow. Ultra-sonic cleaning and Hoppes Nitro-Solvent are the only ways to
clean them.

Another cause of an intermittent change in engine smoothness is the
hydraulic lifters and the exhaust valve and guide clearance.

I'd recommend doing the SB 388C Valve wobble check if the engine has 500
hours since new or OH, and also checking the leak down on the lifters and
setting the dray tappet clearance as part of the inspection. This is
relatively inexpensive, especially when done at annual, and can save a LOT
of problems in the future with stuck valves, bent pushrods, and aggravating
"auto rough" engine operation.

In fact, I'd recommend doing the SB 388C checks on ANY engine that has 500
hours since new or SMOH, because there seem to be plenty of evidence that
the hydraulic tappets may need cleaning and setting of the dry tappet
clearance periodically, and there is certainly plenty of evidence that
exhaust valve guides need checking on a periodic basis.

Funny thing, the Mags have a 500 hour inspection interval, too... They
need to be checked for E-gap timing and general condition inside. Maybe
you should have this ALL done?

Bob Steward, A&P IA
Lycoming Alumnus, Class of '99
Birmingham, AL

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