TPS mod.. well, sorta

[taranis]

So I finally got the guts to tear into my bike to adjust the TPS. After reading Gadget's site a gazillion times, I figured I had it pretty well down how it goes.

I tore into the right-side and got the dog bowl off, hoses disconnected and wires unplugged and outta the way. The next daunting task was the tank. I must've stood there for a good 10 minutes trying to decide, "Do I or don't I?" My penchant lately has been to bugger stuff up pretty good, and I consider myself a fair wrench most of the time. But on the Nomad, I seem to be cursed.

So I muttered, "Time to grow a pair, Jimbo.." and set to it. Partially drained the tank and started disconnecting stuff. I left the speedo on the tank and just unplugged the two wires leading to it and the ignition. One fuel line disconnected, a vent hose on the right, and two plugs under the seat and voila!

Holy crap! That's it? COOL!

Set the tank aside and start looking over the relevant parts. Unplugged the TPS, set my pin inside the connector and started checking. .801 at idle, 4.49 at full throttle. Hmmm... little high there at idle.

Since I didn't have a #25 security torx bit, I simply used a small pair of vice grips to loosen the screw. It turned easily, but try as I might, I was unable to get to the back screw.. Nuts. Well, it should move from here.

So I get to tappin....

The very most I could budge the TPS was up to 4.51 at full throttle, but I was also able to adjust the idle voltage down to .701. Corrrect me if I'm wrong, but it seems the idle was a bit rich at the previous setting? Anyway, I decided not to get greedy and button it back up. Amazingly enough, it all went back together easily and best of all, no leftover screws! Now that's success when you don't have parts left over!

Crossed my fingers and cranked the motor. It purred right to life. NICE! Now for the test ride.... Got it out on the road, shifted into 4th at about 30 mph and romped on it.

Holy.
Crap.

It's a damn good thing I have a backrest.. I would've been tossed onto the pilon! This Nad's got NADS now! Daddy like! After a quick run around the neighborhood, the bike seems to be running well.

I need to take it out for a good shakedown cruise to check mileage, but so far so good.

[dogdoc]

Add the TFI and you will need a trailer to land on. :-)

[bobzinger]

Is the TPS a variable resistor? Did I understand...you went from .801 to .701 and 4.49 to 4.51?
I thought if you raise the top reading, you also raise the bottom reading.

[blowndodge]

You do Bob. Can't go in opposite directions.

[Todd]

Yeah, I'm confused a little.....

[blowndodge]

your confused all the time melonhead!!

[taranis]

Strange but true, don't ask me how I did it (wierd stuff happens to me all the time, just ask Ann).

When I started the adjustment I couldn't get the TPS to budge from 4.49. So I loosened the outermost screw almost all the way and started fiddling with it. When I tightened it back up, the idle was down to .701 and full throttle at 4.51. I redid the test several time to make sure I was reading it correctly - from idle to WOT and back again. Waited several seconds for the voltage to stablize.... Did I bugger the TPS? ??? Doesn't seem like it, nor ride like it.

Wish I would've taken pics. Didn't even think about it. Maybe it shifted more in the housing? Somebody with more knowledge on this things will have to help me out on that one.

After I give it a good ride this weekend, I may end up tearing back into it to check the settings again. I'll post result with pics if/when I do.

Sorry for the confusion - I don't pretend to be an electrical genius.

[blowndodge]

If you understand the function of the Throttle Position Sensor then you'll realize why we are mystified. It would be like bumping the timing on a car to get more total advance and getting less at idle. Turning in one way can't make WFO go one way and idle go the other. Something is giving false readings or the extreme range (idle and WFO) are not being repeatable. Could be a loose throttle cable not opening the throttle or letting it close all the way.

[dkdixie]

Or you did not get a true meter reading.......

[Todd]

Or did you maybe lower you idle speed adjustment to close the throttle a little more than it was.

[taranis]

I did lower the idle speed using the knob under the air cleaner, but that was after I put it back together. Couldn't take a reading with the tank on.

I'm gonna go with a false reading...I get what you're saying - can't go up on one side and down on the other. It's physically impossible. So that sounds like what I done did. Dammit. In my own defense, I was running on 4 hours of sleep after 25 1/2 hours on the road to Colorado and back. I probably misread the WOT reading - which means I've done exactly opposite of what I intended to do. Great.

Now you guys are gonna make me tear it all apart again to double-check. *sigh*

Oh well. Need the practice anyway. ;) Thanks for your input - wouldn't have caught that.

Now, if I can't go any higher than stock (4.49) but about .02v, is that going to make any noticeable difference? My end goal is two-fold: Cooler running engine, 87 or 89 octane, no premium necessary.

If not, I may set the TPS back to stock and go with a TFI. The more I think about it, the more I think this is a better all-around solution.

[Todd]

If you are at 4.49 WOT now....You are within tolerance and should not have to change the TPS...mine is at 4.50 and I have the TFI and it works great......first tank I got 37.5mpg 2up riding.

[taranis]

yeah, but the factory manual says I should be able to go higher.. .say 4.53 or better to enrich the mixture. Not a good idea (too rich)?

[Todd]

You can go higher with the TPS and remain in spec, but if you get the TFI you will tune the bike to the optimum air/fuel ratio anyway where ever the TPS is set within reason or specs.......I don't see where you would gain or lose any advantage adjusting the TPS from where you are now, if you decide to go with the TFI

[taranis]

Pretty much agrees with what I already understand, but thanks for the confirmation. Just noticed you're in Greensboro, NC. I used to live over in Elon College, worked in Greensboro. Loved the area around Elon.. great roads for riding. Only problem was the job and the income. Some great riding out there.

Anyway, back on topic, there's nothing left in the kitty for a TFI right now. I'll go back and double check my settings and go from there. Hopefully get a TFI before spring hits.

Thanks much for the assist. :)