tps evaluating for ii issues

[the Ferret]

Dave... I have no idea where the tps is on my ST. TO tell the truth didn't know it even had one. Popgun owns an ST, maybe he knows where it is. I imagine on an ST it is covered in bodywork though, as everything is.

[max]

Dave, of course the tps is replacable, the problem is;

if you replace it and it works that's ok, but if you replace it and it does NOT WORK YOU CANNOT GO BACK.

i know you want to replace the thing and be done with it, but be patient a little longer, just make sure it is the tps !!!

Capiche? max

[Lord Popgun]

I’m not sure where it is either, and thats after looking at the bike and in the manual. You do have to remove a fair amount of Tupperware to get to the throttle body, and maybe remove the tank so you can remove the air filter.

The TPS is not shown as a separate item on the ST1300 part fiche, that I can find.

A few years ago a member either posted that the TPS is a common one used on a number of Honda cars. I have searched until my keyboard wore out and cannot find it.

Could you replace one and calibrate it? Sure could, not really very difficult. You will need a multimeter (DVOM) and a few instructions. Me, Max or Sportsterdoc could tell you how. The 3 of us have been working on this with me staying in the background mostly. I will admit I have been slacking since just before Christmas. Sorry Doc and Max.

[max]

Sorry Dave, just replied too soon, in answer to your question; "Are you saying that if when the idle problem occurs, and I unplug the TPS and the problem goes away, then the root cause is not the TPS? ".

a; no, the opposite, if you unplug the tps and the engine runs fine, ( all be it a bit softer than normal ) then it is more than likely the tps.

By unplugging it you have taken it out of service and effectively removed from the bike's computer.

max

[SportsterDoc]

At this point, I am still inclined to think that a poor connection is more likely than a failing component, whether TPS or IACV.

I would not replace the TPS without testing it, as Max posted in his video.
It is an easy test, but the test would likely be valid only when the motor not running properly.

Follow TPS diagnostics per pages 5-23 thru 5-25 of the FSM (see below). In the 68 page thread, note comments in posts 615, 618 & 622, especially see Max's post 632 regarding TPS output test. Advise if output is not 0.5 VDC at idle.

This is a summation of the FSM TPS tests:

DTC 8-1 TP (Throttle Position) sensor low voltage
With ignition switch on and stop/run on, probe sensor contacts to verify steady voltage increase from throttle fully closed to throttle fully open.
With ignition switch off, disconnect the connector, then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.
If no voltage, with ignition off, check continuity on black/yellow to ECM connector, for continuity of center pin sensor output black/red wire to ECM connector and for no continuity (infinity) of black/red wire to ground.

DTC 8-2 TP (Throttle Position) sensor high voltage
With ignition switch off, disconnect the connector, measure sensor resistance between black/red and black green of 0.5 to 1.5 K ohms. Then with ignition switch on and stop/run on, measure voltage between connector pins black/yellow (+) to black/green (-) for 4.75 to 5.25 vdc.

I posted previously info on purchasing a TPS, but please hold off on that.

I’m not sure where it is either, and thats after looking at the bike and in the manual. You do have to remove a fair amount of Tupperware to get to the throttle body, and maybe remove the tank so you can remove the air filter.

The TPS is not shown as a separate item on the ST1300 part fiche, that I can find.

A few years ago a member either posted that the TPS is a common one used on a number of Honda cars. I have searched until my keyboard wore out and cannot find it.

Could you replace one and calibrate it? Sure could, not really very difficult. You will need a multimeter (DVOM) and a few instructions. Me, Max or Sportsterdoc could tell you how. The 3 of us have been working on this with me staying in the background mostly. I will admit I have been slacking since just before Christmas. Sorry Doc and Max.

Bottom right corner of this photo
https://i.ebayimg.com/images/g/x9oAAOSwk...s-l300.jpg

Update: Tightening the loose throttlebody connection clamps does not cure the low idle problem. Here’s a description of my experience with the low idle condition returning last evening. The temperature was in the low 60’s. Bike started normally, and I proceeded 1 mile to the freeway, stopping at two stop lights, where the idle was normal. Proceeded 28 miles on the freeway, averaging 70 mph, and exited. Immediately at the first stop light the idle dropped to 700 RPM, and worked its back up to approximately 1,000 RPM. I proceeded about 2 miles to my destination, stopping at 4 more stop lights and each time he 700 RPM condition returned. When I reached my destination I put the bike in neutral and revved the engine several times; each time the 700 RPM condition returned. I turned the engine off with the key, restarted it, and no change. I turned the engine off again; turned the key to “on” and performed the TPS reset procedure, and then turned the key off. I restarted the bike and it was running perfectly. Note: I have performed this exact same TPS reset procedure several times in the past when the low idle condition occurred and it never worked before. The bike sat for approximately 2 hours before I restarted it for my return trip. It started normally, and idled fine at the first stop, approximately 100 yards away. Stopping at the next light, approximately 200 yards away, the low idle condition returned. I put the bike in neutral and revved it several times with no change, except this time it stalled once. I performed the TPS reset as described above and the problem was cured. I proceeded to the freeway and stopped at three more lights, where the idle was fine. The temperature was now in the mid 50’s, and I rode the freeway 28 miles, averaging 70 mph. Exiting the freeway and at the first 2 stop lights the idle dipped lower than normal, but not to 700 RPM, and worked its way back up. When I reached home, 1 mile from the freeway, the 700 RPM condition returned. I again revved the engine in neutral, with no change in idle speed. In my opinion, when the low idle condition returns the engine seems to be running lean, because it does not respond to throttle input as readily. I turned the engine off with the key and restarted it with no change. I performed the TPS reset described above and the low idle condition was cured. I next turned the engine off and unplugged the TPS, and restarted it. I was idling at approximately 1,000 RPM, but throttle response was weak, very similar to the response when the low idle condition was present. I revved the engine several times with the TPS unconnected, and it would return to approximately 1,000 RPM each time, but the throttle response remained weak. (The check engine light was illuminated.) I turned the engine off and plugged the TPS back in and restarted it, and it was running perfectly again. There was a very obvious difference in throttle response from when the TPS was disconnected. I revved the motor several times, and each time it returned to a perfect 1,050 RPM. I turned the engine off and parked the bike. Note: When the low idle condition returns the engine speed drops much quicker than normal, which I noticed especially when shifting gears because the immediate drop to low RPM when shifting causes noisy shifts, caused by the chain slack loosening and tightening. So in summary, tightening the loose throttlebody clamps does not cure the low idle condition. Max, Sportsterdoc, any thoughts or comments?

Well that's disappointing, to say the least. I quoted you on the above because I can confirm that mine did the same. If fact, what you fully described was pretty much what mine was doing before the TPS cleaning.

After that cleaning, on 8 rides of 1/2 hour or more, only twice did the rpm dip to 900 with fully warmed engine, and then it rose slowly to 1000. Both times was at the end of a ride and upon immediate restart, back to 1000.

Like the doc says, perhaps this is a double (triple) whammy of tightening vacuum hoses and TPS cleaning. Imagine, the TPS having a bad / loose connection, compounded by loose hose which is making the TPS even more squirrel-like (guessing here), you tighten hoses, better, but not quite (with IACV lurking possibly), arg.

I've questioned my decision--way too much--to trade mine in for the Street Twin these last 3 weeks. The desire to be a small part of the solution was overuled by my impatience of just wanting a trouble free bike.

I'm hopeful for you.

1. Once the clamps are snugged, to compensate for material shrinkage, they should be good for a long time. Check maybe once a year. Snug, not gorilla tight.

2. Most likely there has been more than one issue affecting idle.

3. If this was the first time the TPS was unplugged, it may also be a TPS connection issue. Best to clean with soft brush, such as old, but clean, tooth brush and contact cleaner. If no contact cleaner, then alcohol (IPA).
Blow out with clean compressed air. For this, I like the canned air.

4. With the connector off, gently pull back (then push forward) on each wire to insure that the contact is seating within its cavity.

5. If not the TPS connector, then maybe the IACV connector.

I do not have all the answers but strongly suggest checking each possible problem. I tried to summarize on Dec 27, but can re-post if helpful.

And yet...what I keep forgetting is that some of our European friends report that a remap of ECU available at dealers has fixed the problem (did I phrase that right?), apparently U.S. Honda is unaware or can't do because of emissions' restrictions?

A minor vacuum leak will give a high idle. A major leak will make it run rough/die. So probably a combination of issues.

Would like a few minutes with a multimeter on Dave's bike. First check would be TPS connection and voltages.

As for remap, I am not discounting possible benefit, but that would not cure a failing sensor or poor connection.

[dave]

Max, Sportsterdoc, Ferret, and popgun, thank you all so much for all your help. Update: Rode the bike tonight on a nearly identical trip that I rode last night, only exiting the freeway about 3 miles earlier. Temperature was in the mid 50’s to low 60’s. Bike exhibited no unusual idle symptoms during start-up, and while at stop lights during the initial one mile ride to the freeway entrance. Reaching the first stoplight after exiting the freeway the idle dropped to about 900 RPM, and rose to approximately 1,000 RPM. While I don’t consider this terrible, it’s a far cry away from the perfect idle conditions I sometimes experience when the idle speed cleanly drops to 1,050 RPM, and remains rock steady. When I reached my destination and stopped about ½ mile from the freeway this exact same 900 – 1,000 RPM idle condition remained. I turned the engine off for approximately 1 ½ hours before restarting it to return home. The idle speed was about 1,050 RPM, and remained so at the only stop light on the way to the freeway entrance, about ½ mile away. I rode about 24 miles on the freeway, averaging 70 mph, and reached my exit where the idle speed immediately dropped to about 500 RPM when I pulled the clutch in; the engine would have stalled if I hadn’t twisted the throttle to keep it running. I proceeded to the first stoplight, approximately 300 yards away, where the engine immediately stalled. The engine restarted, but required careful twisting of the throttle to keep it running. I proceeded home and pulled in the driveway, and the idle dipped to about 700 RPM, and then slowly rose to about 1,050. I blipped the throttle a few times to see if the condition was repetitive, and it was, each and every time. I turned the engine off with the key and went into the house to get a flashlight. I restarted the bike about three minutes later, and it was idling normally (1,050 RPM), even after a few twists of the throttle. So I rode the bike around the neighborhood to try to get the low idle/stalling condition to return, but it didn’t. Instead, the idle would drop to about 900 RPM, and then work back up to about 1,000. This repeated 4 or 5 times over the course of approximately one mile. I pulled into my driveway and turned the engine off, using the key. Next, I unplugged the TPS, and restarted the engine. I got the flashing “check engine” indicator (8 flashes), and the idle seemed to be acting exactly the same as it was just previous to unplugging the TPS, except the throttle response was very poor (just like in the video Max posted). So I took the bike for a ride to see what would happen, and discovered the engine will not rev past 3,000 RPM with the TPS switch disconnected! There was no change to the way the bike was idling – it would drop to approximately 900 RPM, then increase to just about 1,000 RPM (far from a perfect condition). I rode it about 1 mile with the TPS disconnected, stopping to check the idle speed a few times, and there was no change. Try as I might, the engine will not rev past 3,000 RPM (I didn’t open the throttle 100 % though). It starts shutting off at about 2,800 RPM, and by 3,000 it acts like either the fuel is shut off, or the ignition shuts down. I returned home and reconnected the TPS switch and restarted the engine. Idle was now at about 1,050 RPM, even after a few twists of the throttle – so it actually got better after reconnecting the TPS (the normal throttle response immediately returned, and the ability to rev past 3,000 RPM also). So that’s the latest.

[max]

Ok then, well i could not remember if my bike was limited to 3000 rpm, so i just unplugged the tps and yes, it did go up over 5000 rpm, at which point i stopped.

what we are looking for is a bike that behaves without changes, it may be happy to idle at 900 rpm or any other number.
--------the important point is that it does not change erratically over a longer ride.--------

Don't worry about the limiting to 3000 rpm, although it is interesting to know and may be a clue.

Thanks Dave, good update again; max

[Cormanus]

Two things:

1. My bike has—very occasionally—when I've come to a standstill, dropped RPM and then come up again to normal idle speed. I don't recall that it has ever stalled. I'll be more vigilant from now on and, when it happens again, see if there is any pattern to it.

2. Perhaps more importantly, in the smorgasbord of delight about what a marvellous forum this is (and it is) that's going on in another thread, I'm not sure that anyone has pointed to this thread as an example of the quality of the place. Three members (or is it four? I think it is), in different parts of the world, are applying their expertise and taking a great deal of trouble to help diagnose the cause of a problem none of them has in order to help out people they know only virtually. More than that, they're doing it with grace and patience and a steely determination to figure out the problem. I'm not—at this stage at least—a beneficiary, but thanks fellas. Your excellent work is noted and appreciated.

[dave]

First, I agree 100% with what Cormanus says - thank all you guys for your incredible support. So Max, why do you think your bike will rev over 5K with the TPS disconnected and mine will not? I am going to try really hard to perform the TPS test described by Sportsterdoc on Saturday. I have some transmission work to do on my car that has to come first, and the wife has us booked for Sunday. I'll use the bike Saturday morning to runs some errands, and if the low idle condition rears its ugly head again I will unplug the TPS and record what happens. I posted a while back that unplugging the EOT sensor immediately cured the high idle problem, which by the way, I have not experienced the high idle situation in many months. I want to try unplugging the EOT sensor when I am experiencing the low idle condition to see what that does. Thanks again to all you great guys who are giving their time to battle this problem, and all of you guys have a great weekend!

[Houtman_imp]

I follow this tread with great interest and I truly hope that you (smart ) guys will find a cure !