'04 Deuce (EFI) stock TC88 21K miles

for the last week or so I noticed an odd sound at start up Idle.
Intermittent muffled quiet "pop" is the best I can describe it.

It goes away at idle after the bike is ridden 10-15 miles
...until today.

engine light was coming on and off today while riding.
and the "muffled pop" at idle didn't completely go away when hot like it has been

ran the codes and fault code P1356 comes up
search says that's no combustion rear cylinder

hit button again and PN 32919-04A comes up.
Search comes up empty on that part number

I'll change plugs tomorrow (wouldn't that be grand if that makes the odd noise and engine light go away

Plugs aren't old though.
less than 5K miles on them (NGK)

any thoughts, guidance or comments welcome

Thanks

..L.T.A.

 

Also may want to check your plug wires and check that they are tight in the coil. May be time for new wires as those are 17 years old.

 

Thanks CB

I switched plugs front to rear this morning to see if any difference.
None to speak of.

light didn't come on, but I still hear that intermittent quiet/muffled pop/punk sound.
Could that sound be from the rear cylinder not combusting at times?...and hopefully nothing more serious....

I'll buy new plugs( and wires today if dealership has wires in stock)

if that doesn't do it, whats the best procedure to determine if electrical or fuel related?
(fuel injected)

Last question for assistance, if I can't isolate and correct myself, will any harm come by riding it to the pro indy ?
He's about 15 miles down the road

Thanks
Yours truly;
Mr Bummed Out In Ohio



..L.T.A.

 

Yes that sound could be from the non-combust of the rear cylinder. The only other thing I can think of is a fuel injector, you may want to also check the connections on the fuel injection circuit and the connection at the fuel injector.

 

Bad coil maybe?

 

I have a Harley service manual with schematics.
and a decent volt meter (I don't know how to fully utilize)
.... electrical is one of those things that makes my brain short circuit and smoke trying to decipher

..L.T.A.

 

Start with the plugs, what do they look like?
Now the wires spark to the plug.
Check the coil according to the manuals specs.
Wire sparking to ground? Best founnd in the dark.

Edit:Readin a few other replies in regards to the code, some said it was their power commander. Thought I better throw that in.