tps evaluating for ii issues

[dave]

I used the CB to run errands Saturday morning. Turned off, and restarted the motor 7 times. While not stop-and-go city driving, it was still around town that required probably twenty stops and starts, each that caused the engine to idle for the length of an average stoplight. Temperature was in the low seventies. Approximate total miles were 15. Bike ran perfectly, idling at exactly 1050 RPM each time. It’s too early to conclude that the idle problem is 100% cured at this time, but it is looking good. I will post new information as I add up the miles.

[dave]

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?

[Cormanus]

Dave, I know nothing ... absolutely nothing about this, but did you check the throttle body clamps again?

[SportsterDoc]

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.

[pdedse]

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?

[max]

Pdedse, you're first, not trying to be pedantic but by " cleaning the tps " i guess you meant cleaning the tps connector, right? just to clear my mind ( it needs doing ).

And thanks for chiming in, it was interesting to read about your experience mirroring Dave's and all this info helps me to diagnose the solution, your reply adds to this process quite a bit.

Thanks max

[pdedse]

Pdedse, you're first, not trying to be pedantic but by " cleaning the tps " i guess you meant cleaning the tps connector, right? just to clear my mind ( it needs doing ).

And thanks for chiming in, it was interesting to read about your experience mirroring Dave's and all this info helps me to diagnose the solution, your reply adds to this process quite a bit.

Thanks max

Yes, exactly, the connector. I was too vague : )

[max]

Dave once again you have been very precise, that makes it possible to come up with the answer sooner.
What you described is what i was expecting, it actually isolates the iacv and shows that it CAN function " normally " if told the right info.
That is supported by you unplugging the eot sensor and the bike becomes rideable again with the iacv again getting the correct input, i am aware that the iacv replacement fixed johnf's bike but let's concentrate on your case for now.

1 we have now established that the issue is very repeatable, even at low temperatures.

2 we now have a second condition that makes the bike ( somewhat ) rideable again.

3 the tps reset does in fact work repeatable and the engine reset does NOT according to your test.

The difference is that the iacv cycles at engine startup and " resets " itself according to engine temperature and that means at this stage the iacv does exactly what it is told.

As far as i can tell the iacv is " told " by the ecm to maintain a setpoint that results in 1050 rpm in correct working condition with a warm engine, it seems perfectly capable to do so for now.

In addition to all this magnus reported that his old iacv was clean when he replaced his and documented it with some good pictures, so "sticking " is not on my list of options at this time.

SO....

My suggestion is to ride some more and do exactly as you have done now, with tps unplugged just to make sure it wasn't a fluke and look for any signs of the rpm's changing, you want to make sure that unplugging the tps clears the situation every time, don't do anything else because it will prolong the faultfinding as you have mentioned.



Here's what i think happens; your tps has a spot or region in it that has a poor contact, similar to a crackle in a volume control on a radio.
The voltage from the tps is connected to a so called " a to d converter" in the ecm this a/d looks at the voltage and generates a number between 0 and 255 inside the ecm and writes this into a place in memory and updates this process 1000 times a second, this updated value is used by the ecm to decide how much fuel to inject in the engine at any one time together with other sensors and uses a " map " to decide how much fuel is required.
if the tps has a bad sector it is likely that it writes too high or too low values into the memory location and this influences the position the iacv is told to go.
So if the engine expects the idle value to be a digital value of 55 because it has learned through a tps reset that this is the lowest value and reads 85, it decides the throttle is not in the idle position and "tells " the iacv to adjust a lower or higher value of 1050 rpm.
This is my speculation of how the system works, the values are examples and vary in the real world but they represent a model to explain the principle.

So thanks again, Dave, i feel i lean a bit hard on you for information but sofar you are the only one that has helped in a meticulous way to solve the problem.
There is a possible interim solution that i think could be successful without purchasing anything but i will have to think that through some more.
I feel that we are very close to a working solution but need a little more confirmation.

Hope to hear from you with some more riding and a deciding outcome on the tps disconnected.

max

[peterbaron]

1. MOST common mistake in trying to "repair/find" problems is replacing parts, more parts... or complete segment/ass-y prior diagnosing. So even if the presumed problem is fixed with guaranteed 100%, no one knows what was wrong.
2. Watching 5 min video clip/idle up and down tells me what tach is doing, instead of where eventual problem is located.
3. Most members are not troubleshooting oriented (normality, they have their skills in different fields), so a lot of the information they provide is of less or no value
4. WHAT tech would love to know prior making decision is : actual reading report when it occurs (RPM, temp, V, Amps, injection time++++ = service data live stream, DTC status = history, pending or active, freeze frame data, when/how it happens...long, short rides, almost warmed up, only hot, how often...once a month... ANY modifications done to your bike ( PC, bypass O2 sensor, electronic or/and MFI related mods), any work already done to your bike in regards to this problem...
5. Would be excellent if tech has long Honda motorcycle experience and is electrically smart. Techs are people who would like to face the issue in reality, touch it, instead of having describing/filming/narrating it by members
5. Hope this RPM/stalling issue is not related to upcoming ECM update/reprogramming/recall/campaign by Japan HMC
6. If problems are not common, is more difficult to find/rectify them
7. Hope you ride your bike often , not 500 miles/year, use FI cleaner and fuel stabiliser for LONGER storage - not necessarily winter storage
8. How many members did visit HONDA or qualified service center and speak with tech personally??
9. The bottom line is (I know is not easy/simple): diagnose it right and fix it at the first time

This is NOT or about to criticize anybody's/members effort in finding problem but to provide more essential/valued technical info.
Hope this GENERAL info will help to understand the complexity in finding MFI/electrical solutions (not only TPS)

pb

[dave]

Hello Max. Thank you so very, very much for all your help. I need to clarify though, that I did not ride the bike after unplugging the TPS. Also, after I unplugged the TPS I only ran the engine for about one minute, in the garage, and on the center stand. So, because my idle condition seems to quickly come and go at will, it may be too early to assume the TPS is not the fault. Do you know why the TPS on this bike is not replaceable? I checked my VFR800 FSM, and it states that the TPS is permanently mounted to the throttle body and must not be removed. But, Honda sells a TPS that fits both the ST1300 and the VFR1200, part number 16060-MEB-671 (Ferret - if you're reading this can you please read the numbers on your ST1300 TPS and tell me what they are? My CB11 TPS is a Keihin, model JT6H 40116). Do you think it is possible to replace a TPS on the CB11? I see dozens of automotive TPS for sale on the internet for cars and it looks like they're a common, easy, and inexpensive part to replace. I would gladly replace a TPS, even if it was wasn't 100% sure the TPS was at fault, before I would spend all the labor to replace the IACV. I will disconnect the TPS the next time the idle condition occurs and then ride the bike. 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? Also, I would like to test the TPS as Sportsterdoc has suggested. During my TPS research I discovered these are fairly fragile items, and a common failure is caused by the tiny, soldered connections inside the TPS breaking. Thank you again Max, and Sportsterdoc, for all the work you're doing to help resolve this most irritating issue.