Optimax 225 low rpm miss

[bigbasser54]

Hi Don,
Got my low rpm miss back, misses just above idle to about 1000 rpm then clears right up. Last time with this issue (5-6 years ago) was an air injector on #4 I believe.
My fuel system was recently cleaned last year (by your injector service) and 3/6 injectors replaced with new. Around 30 hours on the engine since the last fuel system cleaning.

I was going to pick up a new air injector and start playing the swap game.... is there anything I can look for to find which is the bad injector? Rather not swap a new injector around six times lol.

03 Optimax 225
Ser# OT667018

[EuropeanAM]

Nick- when were the SPARK PLUGS last replaced? Month/Year, and how many engine hours since then?

[bigbasser54]

New plugs before this season so 4/2019, probably 5 hours on them. I can pull and inspect for cracks in the porcelain.

[EuropeanAM]

That would be my recommendation. Also verify gap on each plug.

Any line that runs "even remotely" lengthwise in the white porcelain (that surrounds the electrode pin) should be presumed to be a FRACTURE.

Example:

[Savage]

Make sure you pull the lower cowlings, when changing and inspecting spark plugs, or cracked insulators can occur.

[bigbasser54]

I typically use the rubber hose method for plug #6. Removing the cowlings adds time...guess these plugs are so delicate it's worth the effort....

I'll pull plugs and report back. Thanks all for the help.

[Bob G.]

I use a rubber hose for installing all 6 plugs, less chance of stripped threads. Always remove the lower cowlings.

[ScaleMan]

I have the same issue, can you tell me what you found?

[EuropeanAM]

I have the same issue, can you tell me what you found?

Probably hasn't had a chance to, yet. If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to open a separate thread for your engine (providing the Required Info). Thanks!

[bigbasser54]

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[bigbasser54]

Thoughts on the plug conditions? #2 and #5 look fine to me. #1& #3 have a roughly circular light spot at the top of the insulator. #4 has dark staining on one side and also a few carbon/metal flakes on the side electrode near the dimple. #6 has dark staining running lengthwise.

[Bryanmc57]

What are the gaps like. Hard to tell from the pictures but they look bigger than .032"

[bigbasser54]

Gaps were all within spec. Going to swap them all out and see if anything changes.

[bigbasser54]

Ran it today with fresh set of plugs installed with cowl removed, misfire gone. Thanks all!