Throttle Position Sensor (TPS) Calibration

Getting this subject off the "New Himalayan FAQ Thread".

Good to know how your engine is setup, and the calibration of the various sensors. The TPS is intigral to the proper working of the EFI system. This sensor is calibrated at 0.6 VDC +/- 0.02 VDC. Mine was claibrated at 0.63 VDC and engine operates good. Moved the TPS up/down within the OEM calibration range, inlcuding adjusting the idle air screw +/- 1/4 trun open/closed from factory setting. 0.63 VDC and idle air screw at the factory setting seems to be optimum for my Himalayan engine operation. I did notice that the TPS reading fluctuated between 0.62 VDC and 0.64 VDC when at idle. Going to leave it be for the time being.

Have researched the TPS calibration for my '85 GW as well. There are no new TPS units for my GW so I have found an alternate from an early model Prelude that works well, just has to be modified to suit.

In doing the research, I found that most TPS units are cheaply made, have the least amount of QA/QC of many parts in the EFI system. These are low cost units, a TPS from a different mtorcycle or car can be used as long as it has a linear voltage reading from 0.0 VDC to 5.0 VDC, and a new unit can be faulty from the get go. Know this from experience. Had to change a TPS unit on an '85 GW fuel injected model. Installed a new aftermarket alternative, and when idling, engine operated fine, did not like to operate between 2500 and 4000 RPM, but did from 4000 RPM on. Changed this faulty TPS unit for another new one, and all was good.

Did more research on the QA/QC aspect of these units and found that when there is a fluctuation in the TPS unit such as there is on my Himalayan, this is "noise" and impacts on the smooth operation of the engine. There should be no fluctuation of the TPS calibration when the throttle is at a certain position such as at idle. This is not to say that the FI system will not work properly, but that there is a probability of TPS failure.

When a TPS fails and is out of calibration, it can affect the engine timing. The faulty TPS unit on my GW did just this. The signal from the TPS unit at a given RPM would change and when this happened the engine would misfire, or fire a cylinder at the wrong time. When a cylinder fired at the wrong time, it was as if the engine came to a hard stop, as if the engine had seized. The signal from the TPS would then change back to normal and the engine would operate as if nothing had happened, very disconcerting.

I did not want to believe that a new TPS unit would be faulty from the get go, so I looked at every other aspect of the FI and fuel system. Reported this on a GW forum, and a fellow from down under correctly diagnosed my problem, even though I did not want to believe it. This fellow had the same issue on a BMW motorcycle.

I have viewed the videos on setting the TPS claibration and would like the engine of my Himalayan to idle as smooth as those in the various videos.

Long intro, but thought I'd share my experience.

On my carbed bike the TPS doesn't seem to affect the fueling, just the ignition timing.
Given the sensor is activated by the throttle butterfly / plate there is the possibility that the slight change at idle is just a slight movement in the butterfly caused by the intake pulses.
The ignition timing which gives the smoothest idle is not always the one which gives the best on road performance, so be careful what you wish for!
Haven't seen anyone who has dyno tested various TPS settings, most seem to only consider idle.
My bike has worked fine on factory settings for the first 55000 km, but it has recently needed some carb adjustment and I wondered what the consensus was on adjusting the TPS at the same time - there is nothing in the carb bike manual regarding adjustment or settings.
Someone posted a technical bulletin from the factory regarding revised TPS settings , and from memory the revised figure was not 0.6V
Nothing worse than new parts which don't work, but better now than in the days when Joe Lucas was still around! Back then you usually bought two of everything, in case it was faulty out of the box, or to replace it when it failed within a few miles!

Seems the TPS unit is integral to the throttle body assembly - hopefully I'm wrong in this. Found a throttle body assembly on eBay for some $270.00 CDN. A TPS unit that could fit should be considerably less monies. Will be looking for a suitable alternative for the TPS unit, but this will have to wait until after our trip across Canada starting this coming Saturday.

Another issue with a TPS is that it is affected by heat. I found this to be true with the faulty TPS unit I had on my '85 GW FI model. The hotter the engine operated, and the ambient temperature say a very warm day in the summer - BTDT, these two issues exagerated the faulty TPS engine operation.

Roy - Factory settings are generally the best, but can't hurt to check the calibration and know what has to be done should a new one be required. Being the inquisitive type we humans are, a few of us will and have checked out this issue. Important to take note of the initial reading so that the TPS can be set to this if needed.

The TPS calibration for my '85 GW is done separate from any idle adjustment, but it does affect fueling. The TPS can produce an error code on the '85 GW, but it has to be waaaay out of calibration. I expect the Himalayan to be similar. The only time I change the idle adjustment on my '85 GW is when I balance the right/left cylinder banks of the 1200. Can't envision a reason to dyno because of a TPS unit.

Looking at the basics...
[The guy in the first video says 5.5 - the meter says 0.55]
This one goes with 0.57...

I had to do it. Viewed the videos again. Calibrated the TPS on my Himalayan to 0.55 VDC. Seems to idle smoother - not as much hunting on cold start, roll on of the throttle is good. Went for a ride around the block, speed from 30 KPH to 100 KPH. Rode well. Think that the idle is smoother when coming to a stop - not as much "hunting". Should not need to adjust the idle air screw. Will leave the TPS at this calibration for now. Have a few days I can ride, but priority will be to get everything in order for our trip. Will know before end week if the calibration is what I want.

So I too just went through this process on my Himalayan.
From the factory the TPS was reading 0.65

I dropped it by 0.06 volts to 0.59
Results: At idle it seemed to smooth out a bit - but on the 6mile test ride felt like it was surging still.

Added 0.04 to the factory value for a 0.69
Results: Idle was a bit high around 1500 when stopped would hang around 2k if rolling and pulling in the clutch but always came back down to around 1500 when stopped. The test ride other than the high idle was great - day and night difference from .59 to 0.69 no surging.
Came back and adjusted the idle to around 1300 as indicated on tach. Back out for a test ride once again all was good.

But the cold start/warmup would be the tell all. Of course the bike was hot from the test rides so I had to wait until today.
So starting went like this. Pushed the button, ran for about 5 sec dies - push the button again purrs right along at idle. So in my case a higher value worked better.

Details about the bike
Stock US 2022 built in 2021
Means new styled tank guards etc - but still euro 4 emissions with separate ECU
Miles 400+/-
Valves - Exhaust set at .25mm and Intake at .09mm
EVAP Removed
Riding attitude : sea level - 1,500ft

Thanks for the reply. For my 2021 Himalayan - no mods, idle at cold with the TPS calibrated at 0.55 VDC start/stall and repeat, but operated with throttle assist until warm. Did stall a few times on road until well warmed up. Read a thread on ADVrider forum about increasing the TPS calibration to 0.68/0.69 VDC and start at cold with no stalling. Could not leave alone, so adjusted the TPS calibration before morning start to 0.68, settled out at 0.70 (not a lot of difference) and no stalling on start, and no throttle assist. Will take for road test to warm it up, then adjust for idle RPM.

Liked this video regarding the most common issue regarding stalling on start. This is the thread, read post #4: https://www.royalenfieldowners.com/index.php?threads/variable-idle.2686/ Like the attitude of this dealer, doesn't accept the common come back of "that's just the way it is" - refreshing sentiment.

This dealer also mentioned, setting the idle with the idle assist screw, and changing the spark plug gap.

The telling will be a consistent idle at start - should be hgher than when engine at operating temp, no stalling at start, checking plug colour - should be a nice light chocolate brown, and smooth idle when warm.

On my 2022 the TPS was .62 ish from the factory, it had cold start stalling issues and ran VERY lean. I was told by the dealer "they are just cold blooded". Setting mine at anything less than .62 and the bike was not really ridable. My first attempt to improving it was to set it at .69 and the difference was amazing. Of course after warm up the idle speed had to be adjusted. A few days later I bumped it to .70 then .71. For the last 400 miles I have been running it at .71 and it purrs like a kitten all the time and doesn't stall, ever but to be honest it still feels lean.

I did my first service at 600 miles (I know late) and found the exhaust valve slightly tight, intake was spot on. What was more concerning was the vent line was pinched off on the frame AND the line from the throttle body to the Evap canister was pinched and zip tied that way to the frame right above the throttle. Yep the factory bent the vacuum line in a U shape and zipped it to the frame. I had issues with over pressure and or massive vacuum in the tank from day one. I decided to just remove the evap and run the vent line down to the swing arm area next to the overfill line and plug the throttle body vacuum line. In three weeks of ownership I have discovered one thing about this bike. The companies build quality is nothing short of a joke. LOL But I love the bike and continue to rack up the miles and make what changes are needed to run they way I want it to run.

My video on the TPS.

Mine came set at .67 and had the start/stall and erratic idle issues. Was fine after warming up. After replacing the spark plug with a NGK and final TPS setting of .57 it now starts first attempt, no stalling and smooth idle.

I set mine at .65 and the stalling went away. but I also added a Power Boost at the same time so that made a difference as well. I'm not sure which added more but it runs better and hasn't stalled yet.

Mine was 0.65 IIRC.

• TPS Adjustment
• New Spark Plug
• Idle Screw Adjustment
• Re-routed Evap Hoses
• New Relays
• Drained Tank
• New ECU

The stalling was never resolved on mine and RE could never diagnose.

.656vdc from the factory. Have tried .60 and .57, neither setting has improved the cold start issue. I will try .53 next and then move to the high end with .68 and .71. I have installed the iridium NGK plug and adjusted the idle although have returned the idle screw to factory settings. One thing at a time

I really enjoy this bike overall and can overlook the cold start challenges. However… it is *ridiculous* for a fuel injected bike in 2022 to have cold start issues. EFI can do this AND meet emissions.

Wonder if there’s any point in asking Keihin themselves about this value should be or how to determine it.

Ligonier said:

.656vdc from the factory. Have tried .60 and .57, neither setting has improved the cold start issue. I will try .53 next and then move to the high end with .68 and .71. I have installed the iridium NGK plug and adjusted the idle although have returned the idle screw to factory settings. One thing at a time

I really enjoy this bike overall and can overlook the cold start challenges. However… it is *ridiculous* for a fuel injected bike in 2022 to have cold start issues. EFI can do this AND meet emissions.

Wonder if there’s any point in asking Keihin themselves about this value should be or how to determine it.

Click to expand...

New bike? I would recommend .68 as your next stop, check the idle is close to 1280-1320 when room temp, and leave it and reevaluate after the engine has broken in. As you see from this thread, there are lots of factors which can affect how perfect a cold start is. Allowing the engine to break in does seem to be overall helpful for some.

tom_d said:

New bike? I would recommend .68 as your next stop, check the idle is close to 1280-1320 when room temp, and leave it and reevaluate after the engine has broken in. As you see from this thread, there are lots of factors which can affect how perfect a cold start is. Allowing the engine to break in does seem to be overall helpful for some.

Click to expand...

Tom,
Yes new bike. 2022, about 1200 miles on it so far. Noted on your suggestion.

My take away thus far is that we have values over a range-vids from India like .55, dlr in Ohio likes .63 with an idle bump of 50-100rpms, you suggest .68v. IE there is no quantitative correct answer, only that which works for your bike.

A little richer is better can be better at startup, but as it pollutes much more they attempt to minimize that, which when you have variances in production can give variances in experience. Without going down the rabbit hole, turning up the TPS voltage represents a more open throttle, but at some point that setting along with others creates an oscillating and unstable idle.
For our North American bikes, this overview and approach seems to have helped those whose bike's needed a little help.

tom_d said:

A little richer is better can be better at startup, but as it pollutes much more they attempt to minimize that, which when you have variances in production can give variances in experience. Without going down the rabbit hole, turning up the TPS voltage represents a more open throttle, but at some point that setting along with others creates an oscillating and unstable idle.
For our North American bikes, this overview and approach seems to have helped those whose bike's needed a little help.

Click to expand...

If everything else is working properly and the map is good, at cold start, using primarily the IAT, TPS, engine temp and O2 sensors, the fuel ratio is enriched more than normal and leans out as the temps rise. If the map is faulty for whatever reason, there can be problems. Apparently RE has determined that many bikes with these symptoms do indeed need to be remapped and have authorized it where allowed.

I myself have resolved my idle/stall symptoms by adjusting my TPS. In my situation leaning actually worked better for me. If altitude is a factor then that could explain it.

But I don't like doing bandaids like TPS adjustments because if that is the one adjustment that corrects the problem, then the the map is the cause, assuming all else is good.

Normally and under ideal conditions, and if the map is correct for my bike, the TPS should be set for the true throttle plate position value. The TPS tells the ECU the position of the throttle plate and that along with other sensor inputs gives the ECU the data necessary to give properly fuel scheduling. When you change the TPS setting to another value not equal to the true throttle plate position you are making a misadjustment to resolve another problem. In other words, while the TPS setting is not the actual problem, you're changing its probably correct original value in an attempt to resolve another problem.

When we change the TPS value it also not only affects idle but every other throttle position response as well , and that is why I would prefer another resolution to this problem.

My bike is still low mileage so I'm not doing any other changes or adjustments until I get some mileage on it, based on the reports of others who's idle/stall issues gradually improved with increased mileage as it broke in. If I had stalling issues during riding or movement I would definitely address it now, but I don't.

I have near 8K miles on mine, and I feel that Royal Enfield does need to enrichen the bikes a bit through ECU remapping. I used to have the stalling problem every cold start, but installing the Booster Plug about a month ago fixed that. The silly "choke lever" on LHS has never worked and so I don't touch it. Never stalled since. However, the Booster Plug isn't really enough, the engine can still readily enter a lean condition and ping between 3500 and 4500 when engine exceeds about 75-80C. I hear it and throttle around it, but every plug chop I've done shows this engine runs lean - the timing may or may not exacerbate it, but it's possible they have a touch too much advance, too. My Lucas additive helps only slightly, I basically need to granny it or take a fukitol and twist it for the Yeti Yell when it's over 100F outside

Edit: this is prolly all off-topic, since I have never touched the TPS on my bike yet. I just don't think it'll help with anything here.

Must be fortunate here to have a proper map installed as my '22 starts and idles with no drama.
Hope others with problematic bikes find a solution!

deleted as redundant.

nmroadrunner said:

Must be fortunate here to have a proper map installed as my '22 starts and idles with no drama.
Hope others with problematic bikes find a solution!

Click to expand...

Spotted the unicorn rider! Although I wonder if your altitude has anything to do with it. I'm under 100ft altitude, and my Himmie was always grumpy on cold start before Booster Plug. You're over 5K ft, right?