Rev Hang - /TPS question . Buell xb9r 2004

[evade]

Hi Folks,
I just fitted a new exhaust and went to map it and do a TPS reset, it looks like the mapping failed (or I did it wrong) which is sort of fortunate as it narrows the issue I have down to the TPS reset.
I've found since doing it the revs hang, if I pull in the clutch the revs hang around 2.5-3K for a few seconds before slowly declining to tick over. I've read this is most likely to do with idle too high (although it's set to 1050) or a bad TPS reset...I'm guessing the latter.

Just a quick question about the TPS procedure, the instructions I followed said 'keep backing off the idle screw until the throttle volts stop decreasing' does this mean they constantly decrease until you turn the screw the correct amount or when you blip the throttle they decrease?
However much I turned the idle screw I found the voltage would decrease a tiny bit whenever I blipped the throttle, or decrease and .01 volt and then go up .01 volt. In the end I think I backed it out to the maximum.

Also I take it it's the box marked 'volts' on ECMspy directly to the right of the throttle % ...not 'EGO volts' box.

Thanks,

 

[Tork]

When backing out the idle screw, I monitor the TPS Degrees value since it's directly related to the TPS reset procedure. The value will decrease as the throttle plate closes (indicating the opening amount in degrees). When the throttle plate hits the mechanical stop, the plate is prevented from closing any further, and the value should stop decreasing as you continue to back out the idle adjustment. However, there may be some friction in the TPS sensor, throttle plate shaft, etc. that makes the plate hang open a tiny bit. Snapping the throttle open/closed at this point helps overcome that friction and help force the plate closed. Using some carb cleaner in the throttle plate area can be useful prior to the TPS reset, especially if the throttle plate area looks dirty. I blip the throttle and back the idle out a quarter turn a few times just to make sure that the TPS Degree value bottoms out and no longer decreases, indicating the plate is truly closed. This is the point at which the TPS should be reset. Ignore the actual value while doing the TPS reset procedure - You're just looking to verify that the value stops decreasing. Make sense?

I've seen posts from folks who mistakenly stop backing out the idle adjustment as soon as the TPS Degree value reaches zero, and hit reset. If the TPS sensor is worn, or the previous calibration was borked, the throttle plate may still be slightly open, even if the displayed degree value says '0', so zeroing the TPS at this point would just produce another TPS mis-calibration. In this case, if you were to continue to back out the idle, you'd notice the degree value go negative (-0.5, -1.0, etc.), indicating that the plate still had more to go before it was truly closed, and that the previous calibration was indeed off. Remember, when doing the TPS reset, the goal is to calibrate the electrical 'zero' point to the mechanical condition where the throttle plate is completely and truly closed, so using the degree value as described above is a useful tool to help tell you when it has reached the mechanical stop and is ready for reset. Just be careful and only back out the idle a bit at a time and only enough to verify that the plate is closed. Back it out too much and you risk unscrewing the idle cable completely out of it's threading and getting it back in is a pain in the ass. Also - putting a little grease/lube on your idle adjust cable threading can help make your TPS/idle adjustments smoother (less twitchy) and help keep the cable from binding and breaking due to corrosion.

After you hit reset, bring your TPS Degrees up to about 5.5 - 5.6 degrees, adjust the idle to about 1000 rpm, start the bike and take it for a short ride to bring the engine up to temp and closed loop condition (temp above 160C, cold start enrichment = 100). Make your final idle adjustment and you're done. If the RPMs hang a bit at stop lights/signs, just back off the idle slightly until it returns normally.

 

[user_deleted]

THAT is a great offering Tork. thanks for posting.:up:

 

[mrlogix]

yes, nice and very detailed. +1 from me

 

[evade]

When backing out the idle screw, I monitor the TPS Degrees value since it's directly related to the TPS reset procedure. The value will decrease as the throttle plate closes (indicating the opening amount in degrees). When the throttle plate hits the mechanical stop, the plate is prevented from closing any further, and the value should stop decreasing as you continue to back out the idle adjustment. However, there may be some friction in the TPS sensor, throttle plate shaft, etc. that makes the plate hang open a tiny bit. Snapping the throttle open/closed at this point helps overcome that friction and help force the plate closed. Using some carb cleaner in the throttle plate area can be useful prior to the TPS reset, especially if the throttle plate area looks dirty. I blip the throttle and back the idle out a quarter turn a few times just to make sure that the TPS Degree value bottoms out and no longer decreases, indicating the plate is truly closed. This is the point at which the TPS should be reset. Ignore the actual value while doing the TPS reset procedure - You're just looking to verify that the value stops decreasing. Make sense?

I've seen posts from folks who mistakenly stop backing out the idle adjustment as soon as the TPS Degree value reaches zero, and hit reset. If the TPS sensor is worn, or the previous calibration was borked, the throttle plate may still be slightly open, even if the displayed degree value says '0', so zeroing the TPS at this point would just produce another TPS mis-calibration. In this case, if you were to continue to back out the idle, you'd notice the degree value go negative (-0.5, -1.0, etc.), indicating that the plate still had more to go before it was truly closed, and that the previous calibration was indeed off. Remember, when doing the TPS reset, the goal is to calibrate the electrical 'zero' point to the mechanical condition where the throttle plate is completely and truly closed, so using the degree value as described above is a useful tool to help tell you when it has reached the mechanical stop and is ready for reset. Just be careful and only back out the idle a bit at a time and only enough to verify that the plate is closed. Back it out too much and you risk unscrewing the idle cable completely out of it's threading and getting it back in is a pain in the ass. Also - putting a little grease/lube on your idle adjust cable threading can help make your TPS/idle adjustments smoother (less twitchy) and help keep the cable from binding and breaking due to corrosion.

After you hit reset, bring your TPS Degrees up to about 5.5 - 5.6 degrees, adjust the idle to about 1000 rpm, start the bike and take it for a short ride to bring the engine up to temp and closed loop condition (temp above 160C, cold start enrichment = 100). Make your final idle adjustment and you're done. If the RPMs hang a bit at stop lights/signs, just back off the idle slightly until it returns normally.

That is brilliant, thanks for this. I'll take a look later today and see if I can get it nailed, paying attention to the degree value this time.

This might be a stupid question but is it the butterfly valve visible with the airfilter lid off? If so could you double check by looking at it while doing the procedure?

Thanks,

 

[user_deleted]

yes it is. remove air box cover(4 torx screws)...remove air box lid(5 captive snap tabs)...there it is.

 

[djs2k2]

Yeah I had huge rev hang after a tps reset and had to be reset again!

 

[evade]

Thanks for the advice, TPS reset worked great focusing on the degrees value - I actually had to snap my throttle forward slightly to get it to 0.0 .
Remapped it too which has transformed the bike, fixed a massive flatspot low down in the revs - think I've lost a bit from the top end though but hey ho.

 

[Tork]

Evade - As mentioned in my post, when backing out the idle and snapping the throttle you're not trying to reach a degree reading of '0' (zero) and need to completely ignore the actual numeric value displayed.

1. You slowly back out the idle while observing a decrease in the degree value as the throttle plate closes. At some point, it will stop decreasing in value. It may or may not stop at zero. Doesn't matter. Again, ignore what the actual number is, it's irrelevant. At this point, the throttle plate is theoretically closed, but it may be still be hanging open slightly due to debris or throttle cable friction.

2. Back out the idle another 1/2 turn and snap the throttle. If the degree value continues lowering further after snapping the throttle, back out the idle another 1/2 turn and repeat until the degree value ceases to lower any further. Now hit reset.

The reason why you need to completely ignore the TPS degree value during the reset procedure is that you must assume the possibility that the TPS zero is currently mis-calibrated. Therefore, if you are backing out your idle and stopping at a mis-calibrated '0' (zero) indicated value and hitting reset, and the throttle plate is still slightly open for whatever reason, the end result will again be mis-calibrated and the error will be subsequently factored into your ECM mapping calculations.

If your displayed degree value ends up at '0' (zero) after backing out the idle and snapping the throttle, it's a good indication that the previous TPS reset calibration was done correctly. If it ends up going lower than '0', that's a good sign the TPS is out of calibration (mechanical sensor wear or the previous reset procedure wasn't done correctly). In this case, your bike may actually run better after you've completed the reset since the calibration was previously off.

Another TPS-related tip: Always make sure you're throttle cables are adjusted properly, to include a tiny bit of slack per the manual instructions. That slack allows the throttle plate to correctly return to it's mechanical stop with no throttle applied, especially when the handle bars are at their extreme left/right limits. I worked on a friend's XB that had just come from the shop after a minor low-side accident. The mechanic had adjusted the throttle cables and reset the TPS among other things. Unfortunately, the throttle cables were adjusted too tightly and had no slack at all. The mis-adjusted throttle cables were constantly pulling enough to keep the throttle plate slightly open, even after backing out the idle adjustment and snapping the throttle, resulting in a TPS reset calibration that was completely off and made the bike run like crap (poor idle, coughing, backfire through the intake, cutting out under load, etc.). While looking at the bike, I noticed the absence of that little bit of play you always feel in the throttle grip, and the idle RPMs would increase when you turned the bars left and right. After re-adjusting his cables and resetting the TPS, the symptoms were cured and the bike ran great.

 

[hntnfsh]

Excellent posts Tork. Thanks!

 

[evade]

Evade - As mentioned in my post, when backing out the idle and snapping the throttle you're not trying to reach a degree reading of '0' (zero) and need to completely ignore the actual numeric value displayed.

1. You slowly back out the idle while observing a decrease in the degree value as the throttle plate closes. At some point, it will stop decreasing in value. It may or may not stop at zero. Doesn't matter. Again, ignore what the actual number is, it's irrelevant. At this point, the throttle plate is theoretically closed, but it may be still be hanging open slightly due to debris or throttle cable friction.

2. Back out the idle another 1/2 turn and snap the throttle. If the degree value continues lowering further after snapping the throttle, back out the idle another 1/2 turn and repeat until the degree value ceases to lower any further. Now hit reset.

The reason why you need to completely ignore the TPS degree value during the reset procedure is that you must assume the possibility that the TPS zero is currently mis-calibrated. Therefore, if you are backing out your idle and stopping at a mis-calibrated '0' (zero) indicated value and hitting reset, and the throttle plate is still slightly open for whatever reason, the end result will again be mis-calibrated and the error will be subsequently factored into your ECM mapping calculations.

If your displayed degree value ends up at '0' (zero) after backing out the idle and snapping the throttle, it's a good indication that the previous TPS reset calibration was done correctly. If it ends up going lower than '0', that's a good sign the TPS is out of calibration (mechanical sensor wear or the previous reset procedure wasn't done correctly). In this case, your bike may actually run better after you've completed the reset since the calibration was previously off.

Another TPS-related tip: Always make sure you're throttle cables are adjusted properly, to include a tiny bit of slack per the manual instructions. That slack allows the throttle plate to correctly return to it's mechanical stop with no throttle applied, especially when the handle bars are at their extreme left/right limits. I worked on a friend's XB that had just come from the shop after a minor low-side accident. The mechanic had adjusted the throttle cables and reset the TPS among other things. Unfortunately, the throttle cables were adjusted too tightly and had no slack at all. The mis-adjusted throttle cables were constantly pulling enough to keep the throttle plate slightly open, even after backing out the idle adjustment and snapping the throttle, resulting in a TPS reset calibration that was completely off and made the bike run like crap (poor idle, coughing, backfire through the intake, cutting out under load, etc.). While looking at the bike, I noticed the absence of that little bit of play you always feel in the throttle grip, and the idle RPMs would increase when you turned the bars left and right. After re-adjusting his cables and resetting the TPS, the symptoms were cured and the bike ran great.

Thanks Tork, I think I'll slack off the throttle cables a tad and try again. I kept backing off the idle screw until the degree value stopped going down, this was at 0.1 and then when I forced the throttle shut more then when it naturally stops it went to 0.0, I backed it off a tad more and reset the TPS. But as you say I think the throttle cables are a little too tight.

The bikes running great got all the work done on it just in time for a track day.. then when I gave it a final check over I noticed the belt was torn
That belt only had 1.5k miles on it so now to find out why it has torn!

I'm hoping it's just wheel alignment or age of the belt or something simple