TPS baseline won't go down to 150mv - SOLVED

[nwguy]

I replaced my 99 Bassa's TPS last summer and was able to set the baseline at 150mv. I'm trying again, but weird things are happening. I have the diagnostic cable for doing this. What I've done:

Warmed up the bike thoroughly
Disconnected the linkage between the throttle bodies
Backed out both TB stop screws so screws not touching
Key on but engine not running
Initial measurement was 168mv

I loosened TPS screws and no matter how far I try to rotate the TPS it wouldn't get below upper 160s mv. I pulled the TPS to see if gunk was in the screw slots. None there. Now as time has passed I can't get it below 170mv.

The engine should be off, correct?

Would an engine not sufficiently warm cause this?

Wondering what's different between last time and this time. No more than a few hundred miles on the bike between last time and this time.

[n3303j]

It's only a rheostat. It should go down to low numbers. 150 is only used so they aren't using the ends of the resistive element.
I'd be tempted to.pull the TPS  and measure resistance directly to the contacts with a meter. If you can't get <150 (and a smooth progression as you advance the control) I'd assume the problem is in the TPS.

[nwguy]

It's only a rheostat. It should go down to low numbers. 150 is only used so they aren't using the ends of the resistive element.
I'd be tempted to.pull the TPS  and measure resistance directly to the contacts with a meter. If you can't get <150 (and a smooth progression as you advance the control) I'd assume the problem is in the TPS.

To which contacts? The red and black leads coming off my diagnostic cable when it's plugged into the TPS?

[michaell32]

Look inside the TB. I've seen oil residue so thick it prevents the plates from fully closing.

[nwguy]

Does engine temperature affect setting the TPS baseline?

I cleaned out the insides of the throttle bodies as best I could last summer when replacing the boots. That was a few hundred miles ago.

[PeteS]

20mv is only small percentage of max voltage. I doubt it will make that much difference. Does the TPS sit above or below the throttle body? On the early EVs it was mounted on the underside and gas would drip into them affecting the resistive element. I discovered the element is around the circumference of the TPS not the bottom like the majority of pots. Drilling a small .1” hole on the underside just off center let the gas escape and the TPS lasted much longer.
This won’t apply if yours is mounted on top.

Pete

[michaell32]

How are you measuring voltage?  When I set mine, I used a multimeter and wire piercer adapter right at the TPS. IIRC guzzidiag showed a different voltage than my Fluke. I went off the fluke for the base setting.

[guzzisteve]

I set my 98EV back in 07 and it's still in same place, I do check it & hasn't moved.

[Vagrant]

Don't use cables or GD. Use a high quality digital meter. Just set to the 515-540 or what the book says. The 150 is a one and done as far as I'm conceded.

[PJPR01]

A Casper cable is a good one of measuring the voltage to get it to 157 mv...much easier than probing the wires.

Did you also loosen the screw for the high idle on the throttle body...that could be preventing it from dropping all the way down...at least it was on the V11 Scura.

Linkage is disconnected, so the only thing that I can think of that's hanging it up is the high idle screw on the bottom where the cable connects...if that's present on your model.

[n3303j]

To which contacts? The red and black leads coming off my diagnostic cable when it's plugged into the TPS?

When the TPS is removed from the bike I check every combination of terminals with an ohmmeter. One pair (probably extreme) should remain at a fixed resistance as they are opposing ends of the resistance element. The other two pairs should give you a varying resistance as the control is turned. It should be a smooth sweep without any gaps if the potentiometer is operating correctly.

[Tom H]

As mentioned, do not use GD to set the TPS. Use a multi meter. The Casper cable is great!

This link should still work for the tuning guide if you need it:
https://archive.guzzitech.com/EVTuneup-Jeff_B.html

Tom

[Dukedesmo]

Not familiar with your bike but my Ducati 916 TPS is set by adjusting to 150mv at fully closed and I find that disconnecting the linkage between front/rear cylinder (as recommended by Ducati) doesn't give it enough spring force to fully and consistently close it every time under it's own power. I leave the linkage connected but wind back the adjuster so that the rear butterfly valve (TPS is on the front TB) is not closing, that way I can ensure that full spring force of both valves is on the front and therefore the TPS is fully closed at '0' (150mv).


Also and, again not familiar with yours, the butterfly valve is fixed to the shaft by 2 screws which have a small amount of play if loosened as the holes in the plate are larger than the screws (back of the screw is 'crimped' so it can loosen but won't fall out, which is a good thing), meaning you can loosen the screws and 'wiggle' the plate so that it is perfectly central and therefore fully seals/closes - the first time I checked mine one was slightly off centre and so wouldn't fully close.


Finally, to make future adjustments easier, I opened up the ECU and soldered 2 wires to the TPS voltage line and fitted a 2-way terminal block under the seat so I can attach a voltmeter to do the adjustments 'hands-free'.


Not sure how much of this might apply to a Guzzi but I would think the setup is not too different?

[Wayne Orwig]

Measure the voltage. Take the screws out and pull the TPS. Measure the voltage. If it drops, then the butterfly in the throttle body is sticking open a bit.

[nwguy]

Problem solved. My TPS got covered with oil the other day and cleaning it fixed the problem. I had installed a new crank position sensor and didn't transfer the o-ring from the old sensor to the new one (why no new oring with the new sensor?). Got quite a bit of oil all over the left side of my engine, including the TPS. I cleaned the TPS with denatured alcohol and a q-tip. Then sprayed it several times with deoxit and blew it out with my air compressor.

Wayne's suggestion to remove the TPS before testing with my multimeter made sense to me. After cleaning, it dropped well below 150mv. I then reinstalled it with a reading of 149.6 mv.

michaell32: I'm using a Fluke multimeter

PJPR01: I do have a Casper cable and have been using that while testing/setting.

Tom H: I have been using the tutorial you cited along with Brad the Bike Boy's that has pictures.

n3303j: I liked your comment that the TPS is "only a rheostat". While cleaning it and turning the mechanism I could feel the contact moving over the winding.

Thank you all so much for your help. I love Wild Guzzi.

The problem now is that my bike is stone cold with the TB stop screws loosened and the air bleed screws closed, and I need to warm up the bike for the rest of the tune up. Would it make sense to do step 10 shown below with it cold, back out the air bleed screws a bit, then ride it until it's warm before resuming the tune up? I'm assuming the bike doesn't need to be warmed up to set the TPS baseline but I'll test it again after the warm up ride.

10. Turn in TPS side throttle plate stop until you get 500 to 525mv on your multimeter.  Turn in the non-TPS side throttle plate stop screw until it just touches the butterfly stop. Most folks will tell you 360-380mv  but this is wrong for the new bikes with 1.5M computers.  500-525 is the correct number for the new machines. After this step, do not touch the TPS side throttle stop screw!

[Wayne Orwig]

The problem now is that my bike is stone cold with the TB stop screws loosened and the air bleed screws closed, and I need to warm up the bike for the rest of the tune up. Would it make sense to do step 10 shown below with it cold, back out the air bleed screws a bit, then ride it until it's warm before resuming the tune up? I'm assuming the bike doesn't need to be warmed up to set the TPS baseline but I'll test it again after the warm up ride.

10. Turn in TPS side throttle plate stop until you get 500 to 525mv on your multimeter.  Turn in the non-TPS side throttle plate stop screw until it just touches the butterfly stop. Most folks will tell you 360-380mv  but this is wrong for the new bikes with 1.5M computers.  500-525 is the correct number for the new machines. After this step, do not touch the TPS side throttle stop screw!

If the throttle butterfly is closed and you have 150mv cold, move on to the 500mv setting.

[guzzisteve]

Make sure you tighten the screws real tight not just snug, check voltage.