So i went to start the bike about a month ago, there was a thud, then sounded like the starter didn't catch. Started perfect right after that. While riding later, it sounded as if the cylinders were firing right on top of one another, almost like it was out of time, and has been since. No power loss at all, but my fuel mileage went from the low to mid 40s to around 32 33 mpg. I could easily pull 200 miles out of a tank, but can't get much past 160 now without babying it. I have an 09 SG, w/pcv, SE AC and 4" Rhinehart slipons. Bike has 40000 miles on it, as i like to ride my money, not park it in the garage. Any ideas. BTW, i did replace the plugs yesterday with stock plugs, as the SE plugs were fouling out pretty bad. Appreciate the help! HUA!

 

Plugs fouling how? Black, dry, sooty or black and wet? "Reading" plugs is part of every trouble shooting process. What color are the tail pipes, sooty black by any chance?

I have NO experience with any of the fuel modifiers but just reading the forums indicates that the experts will tell you to take the pcv off and run a tank or two and see what happens. If the problem remains, it isn't the pcv. If the problem goes away, you know the guilty component and can work that out with the manufacturer.

 

Sooty and dry. Pipes are also sooty as well, but i contribute that to the canned map i had on the PCV. Chrome on the right pipe started to turn a copper color abit, just about the same time. I now have the proper map, but i will definitely try running it without the PCV. But if there was an issue, shouln't it throw a code? Last time my PCV went bad, this is not the first time, bike threw multiple codes and went away when it was taken out of the loop. This happened quite suddenly with no codes.

 

There is a check-list to consider when an engine still "pulls" but does not give the proper mileage and coloration starts on the pipes:
- air filter
- fuel quality
- spark plug cables
- O2 sensor wiring
- intake air mass flowmeter
- possible exhaust gasket leak
- possible partial occlusion of the catalizer
If the engine starts easily the timing is OK and the spark plugs are sufficient for the time being. Dirty spark plugs will clean themselves in a few hours using the heat of combustion, but the gap needs be adjusted manually.

I don't have a PCV, but I guess that if you have a faulty one installed and you can start the engine, problems will arise as soon as it will try to come into action like read
the O2 throttle-position air-flow tachometer values because it will send a wrong set of informations to the EFI killing your mileage and increasing the exhaust temperature. This could be caused by only one bad or intermittent contact in a large connector.

 

My guess would be that your pcv shot craps

 

Have you changed out your fuel filter at 25,000?

 

In case of lack of fuel, I would think the system could reduce the throttle opening to balance the air fuel ratio using O2 sensor feedback.

 

the pcv takes the o2 sensors out of the equation, unless he has autotune, but he didn't mention that.

 

This is an old thread, I know.

I'm having this same problem now.

Is anyone else having this problem?

 

My fuel mileage dropped dramatically and plugs fouled right before my 8 year old original battery finally gave up the ghost.