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TPS adjustment (throttle position sensor) - All Modelsby Dr Z, 2008-02-10
The first thing to check before adjusting the TPS is the throttle cable. It should have the correct amount of slack so it does not open/move the throttle plate when you turn the handle bars to either side. Make sure the throttle lever wiggles slightly while watching the throttle plate to ensure it does not move from fully closed throughout the entire range of motion as the bars turn. Make sure there are no sticks or mud caked near the cable that would be causing it to be too tight. After you have confirmed the throttle cable has the correct free play you can check the TPS adjustment and correct if necessary.
The following instructions are for checking/adjusting the TPS using the stock Engine Control Module (ECM).
1) Warm up the engine and turn off the key.
2) If you have a VDI ECU you will need to put the stock ECM in for this check/adjustment. To adjust the TPS using the VDI ECU continue reading this article.
3) Use a paper clip to put the ECM into service mode. See this tech tip. Service mode
4) Turn on the key. The pod should show -COO like in this picture. If the line is above or below the center it will need to be adjusted. (example _COO)
Here is how to adjust the TPS.
1) Remove the black left side covers. Be careful, the engine is hot!
2) Slightly loosen the two screws, do not remove them, and adjust the TPS until the line reads -COO. The line only changes every 0.4 seconds so you need to watch it for 2 seconds to be sure it is centered.
3) Gently snug the two screws without moving the TPS and make sure the line is still centered.
4) Turn off the key and remove the paper clip.
5) Replace the left side black covers.
6) If you have the VDI ECU, don't forget to put it back in!
If there is not enough adjustment to get the TPS to read -COO, you can remove the TPS and make the holes longer by grinding them. I had to do this to mine this summer to get it to center. About 4500 miles on it at the time.-DrZ
I have over 6000 miles on it now and have had to elongate the holes again. RENO suggested vibration as a possible culprit. I was thinking that whatever stops the throttle plate when you let off could be getting worn and causing the need to adjust the TPS beyond it's normal limit. Also, there could be wear or slop in the area the TPS connects to the throttle plate. I think I might try to compare the values of the voltage test mentioned in the last section of this tip to the -COO adjustment if I can get some spare time. I'll report back with results when I get to it.-DrZ 6/25/11
Occasionally someone will discover that adjusting the throttle cable slack to be tighter will move the TPS indicator line on the display, and will conclude that this is an easier way to adjust their King Quads TPS. This is however, not so.
One CAN adjust the throttle cable to make the TPS reading look proper, depending on which way it has drifted, but this is not adjusting the TPS.
The Throttle Position Sensor regulates the fuel metering with respect to the throttle plate's position. The TPS has to "know" the throttle plate's true position in order to tell the ECU how much fuel to deliver to the injector at that point. This relationship is most significant at idle and low throttle settings.
If you adjust the cable slack in order to center the TPS indicator line on the display, you aren't adjusting the TPS, you are "fooling" the display into thinking you did!
We could do the same thing with judicious pressure from the throttle thumb, to bring the line up to center, and we haven't adjusted the TPS then either, we've just moved the display line.
The goal is not to make the TPS reading in the display look the way we want it by using the throttle cable adjustment. The goal is to properly adjust the electronic vernier that regulates fuel delivery, with respect to the throttle plate shaft's zeroed/closed position. If we do not loosen those screws and adjust the vernier's position relative to the throttle plate shaft to center the line on the display, we haven't adjusted the TPS.
(and having the throttle cable set with no slack at all is not particularly safe as it can affect the engine speed when the handlebars are turned)
You don't need a stock ECU to check the TPS.
shorthair found Lyle's tip:
"...you can also use a voltmeter."
"According to the service manual:
0% throttle = ~1.12V
100% throttle = ~4.32V
The voltage between the middle (yellow wire) and ground (Black/Brown stripe) should be about 1.12V with the key on, and no throttle pressed.
If it isn't, you need to loosen the screws on the TPS sensor, and rotate it until it is. It needs to be close, but doesn't need to be bang on perfect.
A lot of 700's were shipped with the TPS off to one side."
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