Erratic TPS reading on Quota 1100ES

[Rafael]

Well, now that my buddy took the big plunge and bought a Stelvio, I get to use his Quota for any dirt road trips until he sells it.

In preparation for a trip to Utah next September, I took it out for a spin. Checked the gas mileage and found that it was a measly 27 mpg. He got mid 30's 2 years ago. We've recently (not may miles ago) tuned it ; adjusted the valves and balanced the notorious throttle body. Anyway, we hooked up the VDSTS and found that the TPS figure behaved normally with the ignition on and engine off. But when the engine is running the reading drops initially then, seem to get stuck, then rise to a figure that's most likely too high. The bike seems to run okay though, it's cold blooded and its a little jerky the way it was before the PC III usb was installed. The right spark plug color seems normal and the left reads rich. I figured that might be from the imbalanced idle setting. The idle imbalance is due to the closed the air bypass per MPH recommendation.

Also found the following historic diagnostic trouble codes:
Throttle Position Sensor: short circuit to battery.
Battery volt: open / short circuit to battery.
Fuel Pump Relay: open / short circuit to battery.

There are no current trouble codes.

It seems to me to be a bad connection to the TPS that is exacerbated by the motor vibration.

I checked the price of the TPS at a dealer... $330US! I think I'll try cleaning it and checking the wires and connector for a defect. Also, searched Weber PF 10 and found that a V6 Maserati motor used the same TPS, wish it was a Fiat... who knows the Maserati part may be cheaper.

Any help would be appreciated.

[john zibell]

Replace the TPS. You can use a Harley one. See this article in the archive. http://archive.guzzitech.com/HD-TPS-Jeff_B.html

[Rafael]

Thanks John, I read it over, the voltage part gave me a little headache. From what I remember the Weber
PF-10 is a lot bigger than the Weber PF 3C. I measured from center to center of the mounting bolts on the PF 10, its around 2 7/8" I don't have a V11 around now. Can someone take a quick measurement? Has anyone used the HD
(PF4C) on a Quota?

Found a PF 10 on a Maserati web site, it was cheaper than MG but still $252.

[Rafael]

Follow up:

I checked with a second MG dealer, turns out that the Weber PF 10 is no longer available through guzzi.

I took off the TPS and tested it with an ohm meter. Found the resistance changed gradually as I turned the shaft, so I brushed off the ground connectors to the ECU and added a little dielectric grease the the TPS connector. The TPS reading is now normal but he spark advance still is static or erratic. I checked the timing with a timing light, the timing advance looks normal, so the reading is crap not the ECU.

Now for a test drive with out the PC3. And try to figure out what's going on with the gas mileage.