Sputtering '07 S4R

[Klip]

I've tried several different searches, but didn't find anything that was similiar to my problem.

I have a 2007 S4R with the Testastretta engine. The only accessory/modification related to the engine is a Termignoni Shorty exhaust. Nothing new at all for the past couple years, though. The bike has 23,000 miles on the odometer and I've never had a problem... until now.

I'm having a problem with engine sputtering/losing power when I decelerate. She's smooth as butter if I'm holding a constant throttle or accelerating, but the instant I decrease throttle even the tiniest increment it starts sputtering badly. It acts as if I've just run out of gas. The engine won't die, though. It just keeps sputtering along, losing and regaining power over and over. And it doesn't do it all the time; it's intermittent.

I'm not mechanically inclined at all (i'm more of a "Buy 'Em & Ride 'Em" kind of guy), but I did lift the tank and looked around for anything obviously wrong. All hoses and wires were connected and none were pinched or damaged. The airbox is clean and free of debris.

What do you guys think? Did I just get some bad gas? Why does it only run poorly on deceleration?

Thoughts? Need more info?

Thanks in advance!

[JimmyTheDriver]

Hey man, 

I have the opposite going on, but it may be helpful to you.  On acceleration, around 2-4k, my 07 S4R will stumble and lose power.  If held at constant throttle between 2-4k while in neutral, the RPMs jump all over the place and then engine will cut out/pop until I drop or raise the throttle out of that range.

It was recently connected to a computer which showed the throttle position sensor was not reading properly, thus the ECU was applying the wrong air/fuel mixture. On top of that, the ECU isn't taking readings from one of the O2 sensors.

It is currently in the shop with a new ECU on order.  I'll let you know what the resolve is.

-Jimmy

[Klip]

Thanks for the replies.

Wow no takers yet.  Problem is counter-intuitive to me 'cause it happens on the deceleration.

How long since the last service?  Plugs/valves/tune?

Does it happen over 5200 rpm?  Under?  Both?

I don't know how it would relate but I'd do a careful inspection of the vacuum lines just to rule out a leak.  Don't miss the ones at the charcoal canister.

It's due for service right now. The '07 models were on a 7,500 mile scheduled service interval and I'm close to 23,000 miles.

It happens  from 3,000 RPM to at least 7,000 RPM, if not higher.

I'll check the vacuum lines. I removed the charcoal canister back in the summer of 2007.

Thanks!

Hey man, 

I have the opposite going on, but it may be helpful to you.  On acceleration, around 2-4k, my 07 S4R will stumble and lose power.  If held at constant throttle between 2-4k while in neutral, the RPMs jump all over the place and then engine will cut out/pop until I drop or raise the throttle out of that range.

It was recently connected to a computer which showed the throttle position sensor was not reading properly, thus the ECU was applying the wrong air/fuel mixture. On top of that, the ECU isn't taking readings from one of the O2 sensors.

It is currently in the shop with a new ECU on order.  I'll let you know what the resolve is.

-Jimmy

An ECU problem doesn't sound too bad. When I bought the bike in '07, I paid for an extra 3 years of warranty coverage. I'm covered nose-to-tail until June 2012.

Looking forward to hearing of the solution to your problem.