[NIGHTMARE]

No changes were made to the bike at all but this thing is running lean. It seems to happen at really light throttle. I also can't run it at fast idle at startup either or it will miss pretty badly.

I had the tank off the bike for a few weeks. After reinstalling it the bike ran perfectly for 2 days or so and like a light switch started running poorly. I've since removed the tank again to replace all the soft lines inside the tank. That seems to have helped a bunch but still running pretty lean.

Any thoughts would be great.

 

[amullo]

Clogged fuel filter, TPS has moved (it happens), TB sync out off wack..

Is it only running poorly or do you know that it is actually lean?

//amullo

 

[sconly]

weather

 

[stevel]

I've been there recently - 996 that ALWAYS started instantly on a shut throttle, suddenly became rich and took lots of spinning and open throttle to get it to run.
Spent ages checking every sensor to the ECU - all ok, did filters although theye were spotless, new plugs. changed fuel lines in tank, checked the pump pressure.....nightmare. Eventually did a full set up of the TB's, TPS, CO and idle trim etc, and she now runs fine........why the change? No idea!
I found that setting it up by the book gave ok results, but that tweaking the idle trim on a suck it and see basis gave me better running through the range, esp at the 3000 to 4000 range, checked the plugs and she runs nice light brown colour now whereas before all this crap she was always showing black, slightly sooty plugs. Have posted around various places and feedback was that the TPS could be failing when hot, plug leads etc, but I'm still using same ones and she came good by the idle set up route.
Interested to hear any other ideas on this, it was a PITA to check and set up, but learnt a lot about cause and effect along the way, and happy to swap ideas if anyone else has any

An afterthought/ I experimented with mine by running it in the 3500 rev range when it was really rough, and tweaked the idle trim pot on the ECU......made a big difference, and told me how effective this is a an adjustment. Easy on the 996 as it's a pot on the circuit board, (1.6M ECU) but guess the 998 is a different ECU??