2008 won’t idle, tried a bunch, weird issues

johnkol wrote:

Flynavy wrote:

Then checked TPS again and it showed 30-33, it was digitally bouncing in this range and I hadn’t touched it at all.

So it had drifted slightly before you changed the stator.

Can you measure the entire Voltage and TPS range? If the minimum voltage value shows up as 70, what happens at higher voltage values?

.4 at idle then 1.6 at full throttle.

Also though, how is drift even possible if nothing was touched and the sensor was still rock solid tightened down? I’m just having a hard time understanding how the reading can get so whack.

Flynavy wrote:

.4 at idle then 1.6 at full throttle.

That is significantly outside the idle range (0.63V - 0.73V), and the max should be closer to 5V. Does TPS show close to 100 when the voltage is at 1.6?

Brief explanation of the TPS numbers (0-100): as a programmer you never want to code actual voltage values into the firmware because if at a later time the company uses a different vendor for the TPS system (with potential different min/max voltage settings), then you will have to modify the firmware, which is completely unacceptable. So what you do is write the code with abstract numerical values (e.g. 0-100), and then have a file external to the firmware that maps voltages to these numerical values. So if you see crazy numerical values (e.g. 70 that you see at idle) for reasonable voltages, then something must have happened to this external file (which resides in the ECU).

In your case though, the idle voltage is outside the expected range, so how does that map file handle these values? We don't know, it could be a random value, or it could have circled around the top.

Given the above, and also considering that the TPS module exhibits a rattle, you probably need to get a new TPS module.

Before you do this though, you had previously said that you had adjusted the idle screw all the way in without that having any appreciable effect. Irrespective of that, the idle screw should not be all the way in, so I would suggest you back it off one turn and try starting the bike; then try again with the screw two turns off, etc. It should make a difference, and in any case, it doesn't cost anything to try.

johnkol wrote:

Flynavy wrote:

.4 at idle then 1.6 at full throttle.

That is significantly outside the idle range (0.63V - 0.73V), and the max should be closer to 5V. Does TPS show close to 100 when the voltage is at 1.6?

Brief explanation of the TPS numbers (0-100): as a programmer you never want to code actual voltage values into the firmware because if at a later time the company uses a different vendor for the TPS system (with potential different min/max voltage settings), then you will have to modify the firmware, which is completely unacceptable. So what you do is write the code with abstract numerical values (e.g. 0-100), and then have a file external to the firmware that maps voltages to these numerical values. So if you see crazy numerical values (e.g. 70 that you see at idle) for reasonable voltages, then something must have happened to this external file (which resides in the ECU).

In your case though, the idle voltage is outside the expected range, so how does that map file handle these values? We don't know, it could be a random value, or it could have circled around the top.

Given the above, and also considering that the TPS module exhibits a rattle, you probably need to get a new TPS module.

Before you do this though, you had previously said that you had adjusted the idle screw all the way in without that having any appreciable effect. Irrespective of that, the idle screw should not be all the way in, so I would suggest you back it off one turn and try starting the bike; then try again with the screw two turns off, etc. It should make a difference, and in any case, it doesn't cost anything to try.

The idle screw didn’t seem to do much in either direction. Your explanation up top makes sense but here’s where I’m still confused…

The physical TPS has a hole, you press fit this onto throttle body… there is a silver half moon looking metal piece. This is the physical piece that you see rotate when you manipulate the throttle.

So how does the throttle know idle vs full? That silver thing is rotating within the cavity of the TPS, is it a magnetic pickup or resistance type thing? Sam’s thing for when I had the screws loose and I rotated the TPS along both axis, it wouldn’t go lower than 60 no matter what I do.

But the puzzling and concerning thing to me is why did it go to 30, then 60-70? What could have changed that even affects these readings?

Flynavy wrote:

The physical TPS has a hole, you press fit this onto throttle body… there is a silver half moon looking metal piece.

That silver half moon is the so called wiper (attached to the Yellow wire), and is in contact with another disk inside the TPS which provides the resistive load (attached to the Blue and Blue/Black wires); as you turn the wiper, it contacts the resistive surface at a different point, so the resistance between the wiper output (Y) and the resistive output (L/B) changes, thus changing the output voltage that you measure.

When the voltage is lowest, this is interpreted by the ECU as "throttle closed", and when voltage is at max, this is interpreted as WOT.

Flynavy wrote:

Sam’s thing for when I had the screws loose and I rotated the TPS along both axis, it wouldn’t go lower than 60 no matter what I do.

By turning the entire TPS, you are repositioning the resistive disk inside the TPS against the wiper, thus re-setting the the minimum voltage value. Why you couldn't get a vlaue lower than 60, I don't know, it would be instructive if you could measure the voltage and see what it reads; if it is always lower than 0.6V, then you're always outside the permitted range, so the outcome is not well defined.

Flynavy wrote:

But the puzzling and concerning thing to me is why did it go to 30, then 60-70? What could have changed that even affects these readings?

My guess is that because the voltage is outside the specs, the map file (or the firmware) starts counting backwards; for instance, if 0.6V corresponds to 0, and because the firmware does not use negative numbers, a value of say 0.59V will be assigned 100, a value of 0.58V will be assigned 99... and a value of 0.4 is assigned a value of 70.

Flynavy wrote:

The idle screw didn’t seem to do much in either direction.

But it should; if it effects no change then either the screw itself is gunked up, or the passage the screw controls is blocked. In both cases you get a rich condition.

johnkol wrote:

Flynavy wrote:

The physical TPS has a hole, you press fit this onto throttle body… there is a silver half moon looking metal piece.

That silver half moon is the so called wiper (attached to the Yellow wire), and is in contact with another disk inside the TPS which provides the resistive load (attached to the Blue and Blue/Black wires); as you turn the wiper, it contacts the resistive surface at a different point, so the resistance between the wiper output (Y) and the resistive output (L/B) changes, thus changing the output voltage that you measure.

When the voltage is lowest, this is interpreted by the ECU as "throttle closed", and when voltage is at max, this is interpreted as WOT.

Flynavy wrote:

Sam’s thing for when I had the screws loose and I rotated the TPS along both axis, it wouldn’t go lower than 60 no matter what I do.

By turning the entire TPS, you are repositioning the resistive disk inside the TPS against the wiper, thus re-setting the the minimum voltage value. Why you couldn't get a vlaue lower than 60, I don't know, it would be instructive if you could measure the voltage and see what it reads; if it is always lower than 0.6V, then you're always outside the permitted range, so the outcome is not well defined.

Flynavy wrote:

But the puzzling and concerning thing to me is why did it go to 30, then 60-70? What could have changed that even affects these readings?

My guess is that because the voltage is outside the specs, the map file (or the firmware) starts counting backwards; for instance, if 0.6V corresponds to 0, and because the firmware does not use negative numbers, a value of say 0.59V will be assigned 100, a value of 0.58V will be assigned 99... and a value of 0.4 is assigned a value of 70.

Flynavy wrote:

The idle screw didn’t seem to do much in either direction.

But it should; if it effects no change then either the screw itself is gunked up, or the passage the screw controls is blocked. In both cases you get a rich condition.

Tonight I will attempt to get better readings. I’ll be honest, I really don’t want to make things worse and I’m not sure what the smart way to test voltage is? I stuck probes into back part of TPS harness but even that felt intrusive. Should I lightly open wire to get good contact?

Also when you say in contact with TPS with the wiper, you mean internally right? This is the back side of my sensor.

Tried to test again… meter is showing 0 volts until I rotate throttle and then it creeps up to 2.2. When I rotate TPS per the manual the voltage bounces around a little but nothing consistent. When I say rattle, picture the TPS if you were to tap it when a finger nail, you’d hear/feel a buzz/vibration almost like a loose coil or spring like mechanism inside has popped loose.

Flynavy wrote:

I stuck probes into back part of TPS harness but even that felt intrusive.  Should I lightly open wire to get good contact?

Sticking probes is the correct way, no need to open wire. You can wiggle the probes a bit, and if the readings are not jumping around, you have a good contact.

Flynavy wrote:

Also when you say in contact with TPS with the wiper, you mean internally right?

Yes, internally.

Flynavy wrote:

Tried to test again… meter is showing 0 volts until I rotate throttle and then it creeps up to 2.2.

You mean 2.2V is the max value you see at WOT? Maybe the TPS ringing/rattling is a red herring, but the voltage values are definitely out of spec, and that is also supported by the crazy TPS values displayed in diagnostic mode.

I don't know how to proceed from here without spending money; you'll need to get another TPS to see if that is the problem. Alternatively, you can try to fix the low compression issue in order to have a solid mechanical base that you can trust.

johnkol wrote:

Flynavy wrote:

I stuck probes into back part of TPS harness but even that felt intrusive.  Should I lightly open wire to get good contact?

Sticking probes is the correct way, no need to open wire. You can wiggle the probes a bit, and if the readings are not jumping around, you have a good contact.

Flynavy wrote:

Also when you say in contact with TPS with the wiper, you mean internally right?

Yes, internally.

Flynavy wrote:

Tried to test again… meter is showing 0 volts until I rotate throttle and then it creeps up to 2.2.

You mean 2.2V is the max value you see at WOT? Maybe the TPS ringing/rattling is a red herring, but the voltage values are definitely out of spec, and that is also supported by the crazy TPS values displayed in diagnostic mode.

I don't know how to proceed from here without spending money; you'll need to get another TPS to see if that is the problem. Alternatively, you can try to fix the low compression issue in order to have a solid mechanical base that you can trust.

New (used) throttle assembly is already inbound. My overthinking tendencies aren’t allowing me to accept a simple sensor issue though. I just can’t connect the dots of how it slowly crept up as I worked other issues.

For what it’s worth, tonight when I was testing the TPS, it started at 60 at idle. Then it just slowly went to 50 on its own, one tick at a time. Weird…


I really don’t want to accept a low compression issue. My gut is saying don’t hide from the issue as it could be a huge issue but originally everything pointed to electrical. And with the amount of people saying compressions tests are unreliable on these engines I guess it gave me a false sense of security.

Again though the manual says take the reading when a warm bike and WOT. I took on a cold bike with no throttle. Is there enough to make a difference? I plan to check that next.

Flynavy wrote:

I just can’t connect the dots of how it slowly crept up as I worked other issues.

The only reasonable explanation is that there is a problem with the ECU, but the ECU is quite expensive, so let's shelve this idea for the time being until we have more data pointing to it.

Flynavy wrote:

And with the amount of people saying compressions tests are unreliable on these engines I guess it gave me a false sense of security.

Again though the manual says take the reading when a warm bike and WOT.  I took on a cold bike with no throttle.  Is there enough to make a difference?

The people who make these claims believe they know better than the Yamaha engineers.

Cold bike with no throttle would certainly affect the measurement; I don't think it would affect it to the tune of 65 PSI, but it would be better to have a more representative number. Obviously you cannot warm up the engine, so try WOT and see where compression lands.

johnkol wrote:

Flynavy wrote:

I just can’t connect the dots of how it slowly crept up as I worked other issues.

The only reasonable explanation is that there is a problem with the ECU, but the ECU is quite expensive, so let's shelve this idea for the time being until we have more data pointing to it.

Flynavy wrote:

And with the amount of people saying compressions tests are unreliable on these engines I guess it gave me a false sense of security.

Again though the manual says take the reading when a warm bike and WOT.  I took on a cold bike with no throttle.  Is there enough to make a difference?

The people who make these claims believe they know better than the Yamaha engineers.

Cold bike with no throttle would certainly affect the measurement; I don't think it would affect it to the tune of 65 PSI, but it would be better to have a more representative number. Obviously you cannot warm up the engine, so try WOT and see where compression lands.

Well, I’ll be out for a few days so the saga won’t continue until the 26th. But I think that will narrow all of this down. Thanks again for all of your help and I hope you have a great Christmas. Stay tuned!

johnkol wrote:

Flynavy wrote:

I just can’t connect the dots of how it slowly crept up as I worked other issues.

The only reasonable explanation is that there is a problem with the ECU, but the ECU is quite expensive, so let's shelve this idea for the time being until we have more data pointing to it.

Flynavy wrote:

And with the amount of people saying compressions tests are unreliable on these engines I guess it gave me a false sense of security.

Again though the manual says take the reading when a warm bike and WOT.  I took on a cold bike with no throttle.  Is there enough to make a difference?

The people who make these claims believe they know better than the Yamaha engineers.

Cold bike with no throttle would certainly affect the measurement; I don't think it would affect it to the tune of 65 PSI, but it would be better to have a more representative number. Obviously you cannot warm up the engine, so try WOT and see where compression lands.

I lied I have an update. Bought a non OEM TPS as a Hail Mary before I skip town. Exact same readings, 70 at idle. I’m stumped, just absolutely stumped. What’s my next step?

When you say a non-OEM, you mean an aftermarket TPS made specifically for the WRR?

Did you measure the voltage, was it out of spec as the original TPS?

If the new TPS is legitimate, then the next thing to try is a new ECU, hopefully you can borrow one.

johnkol wrote:

When you say a non-OEM, you mean an aftermarket TPS made specifically for the WRR?

Did you measure the voltage, was it out of spec as the original TPS?

If the new TPS is legitimate, then the next thing to try is a new ECU, hopefully you can borrow one.

I did not do those tests to be honest. I’m just sitting here puzzled trying to really think deep if I missed something basic or simple. The TPS presses in and a voltage corresponds to a throttle position so I get that.

Do you think the fact that I’m also getting whacky RPM readings in CO mode could also point back to the ECU?

Are you still seeing unrealistic RPM numbers in diagnostic mode? I thought that this issue had been resolved with the new battery.

Given that the TPS voltage was out of range with the original unit, we couldn't really blame the post-processing of these numbers at the ECU, but if the voltage is within spec with the new TPS unit, then we have two independent measurements (TPS and RPMs) that point to something going awry further down the line.

BTW, at some point in all the WRR discussions, there was speculation that not all processing takes place at the ECU, but that some of it occurs in the display unit, so it could be either of them.

johnkol wrote:

Are you still seeing unrealistic RPM numbers in diagnostic mode? I thought that this issue had been resolved with the new battery.

Given that the TPS voltage was out of range with the original unit, we couldn't really blame the post-processing of these numbers at the ECU, but if the voltage is within spec with the new TPS unit, then we have two independent measurements (TPS and RPMs) that point to something going awry further down the line.

BTW, at some point in all the WRR discussions, there was speculation that not all processing takes place at the ECU, but that some of it occurs in the display unit, so it could be either of them.

RPM issue never resolved itself… I too read something about the main screen and ecu being in sync with each other. While I didn’t specifically mess with anything on the display unit maybe I did knock something loose?

I don't think this is a case of knocking something loose; it's a fundamental problem, like the circuit in the ECU or Meter getting damaged. Can you measure the TPS voltage and see where you are with the new unit?

johnkol wrote:

I don't think this is a case of knocking something loose; it's a fundamental problem, like the circuit in the ECU or Meter getting damaged. Can you measure the TPS voltage and see where you are with the new unit?

Out of town now but I will when I get back. I’ve spent hours thinking this through and I’m coming up short as far as why it’s showing 70 at idle. Like did I install the TPS wrong? No way, it read 70 before I ever even touched the original. Cables are all good, full range of motion. Butterfly valve looks proper.

I wouldn’t be surprised if it was the ECU.

I can't see how it could be wrong installation because you said you tried adjusting the TPS and 70 was pretty much the lowest value that you could get.

If the voltage turns out to be out of spec again, then a value of 70 can be excused, but how probable is it that we have two TPS modules that have gone bad? Not very, which points to the ECU as the next suspect, possibly not supplying the correct voltage to the TPS.

johnkol wrote:

I can't see how it could be wrong installation because you said you tried adjusting the TPS and 70 was pretty much the lowest value that you could get.

If the voltage turns out to be out of spec again, then a value of 70 can be excused, but how probable is it that we have two TPS modules that have gone bad? Not very, which points to the ECU as the next suspect, possibly not supplying the correct voltage to the TPS.

I guess I’m having a hard time accepting the coincidence of a potentially bad ECU with the other weird issues I’ve been dealing with. When it first showed 30-33 at idle my first thought was I physically hit that area somehow and threw it out of spec but I quickly realized there’s no way that’s possible.
It was tightened down rock solid. At this point I’m just replying to keep the conversation going so I guess when I slap a new ECU in we will see.

I agree, the probability of the ECU also being damaged is very low, especially since the ECU has protective circuit to somewhat insulate it from over-current or electrical spike situations. But at this point when two independent measurements point to an electronics malfunction, you have to check whether the ECU is working properly, which brings up another point: are you actually getting a new ECU? It's a rather expensive item, so you may want to consider whether it makes more financial sense to take the bike to a dealer: the troubleshooting may be expensive there, but at least they will not charge you for swapping out various sensors and electronics in order to diagnose the problem.

johnkol wrote:

I agree, the probability of the ECU also being damaged is very low, especially since the ECU has protective circuit to somewhat insulate it from over-current or electrical spike situations. But at this point when two independent measurements point to an electronics malfunction, you have to check whether the ECU is working properly, which brings up another point: are you actually getting a new ECU? It's a rather expensive item, so you may want to consider whether it makes more financial sense to take the bike to a dealer: the troubleshooting may be expensive there, but at least they will not charge you for swapping out various sensors and electronics in order to diagnose the problem.

When I get this throttle body I plan to plug the TPS in direct with it not even installed and see what it reads. Is there any potential the wiper or anything in the body is screwed up or is the wiper just a piece of metal as a reference point for the valve?

You're getting a new throttle body?

The wiper is just a piece of metal; the point where it contacts the resistive disk inside the TPS is what produces the voltage variability.

johnkol wrote:

You're getting a new throttle body?

The wiper is just a piece of metal; the point where it contacts the resistive disk inside the TPS is what produces the voltage variability.

Yeah for 70 bucks and including an OEM sensor I said screw it.