Stalling issue

Hyprdrv · Jul 20, 2021

Searched, couldn't find a solution.

Since the weather has warmed up, my '16 939 has stalled out on me 4-5 times.

Always occurs at medium-low speeds when I pull in the clutch to brake. If I coast down, no problem. If I don't, it'll stall.

Seems to happen when air temp is over 26°C / 80°F, but I'm not sure about that.

Bike is stock, but I did put in a Rexxer reflash a month ago. TPS was reset. Idle is 1300. It restarts right away when I hit the starter.

It's getting hazardous, I almost got stuck in the middle of an intersection today.

Ideas?

N4teTheGreat · Jul 21, 2021

You may need to have your throttle bodies synced, or possibly cleaned as they can get dirty and if they do that can cause airflow problems when the throttle is closed abruptly.

Hyprdrv · Jul 21, 2021

After 5000 km? Seems premature.

N4teTheGreat · Jul 21, 2021

Hmm with low miles like that could be something else. I'd have the dealer take a look.

gatdammit · Jul 21, 2021

You have a 939, which shared some early issues with the 821. On the first gen, there was an issue where the bike would stall while on the roll, either when the throttle was rolled to idle or the clutch was engaged. I dealt with this when my 2013 821 was brand new. The fix was supposed to be a TPS update. I believed the dealer because it stopped doing it.

Specifically, mine would normally do it in taller gears at medium speeds, typically when I was starting to slow down from the 55 mph. Common situation was 3rd-5th gear, cruising around 60 mph, pull clutch to downshift and it would stall.

Have you checked the TSB update history?

Hyprdrv · Jul 21, 2021

Yes, that sounds similar to mine. My bike is practically new (4500 km).

Dealer said no outstanding items. But I will re-check.

What was updated on the TPS?

gatdammit · Jul 21, 2021

I don't know. Was just told there was an "update" for the TPS. This was in 2013, very early after I got it.

Hyprdrv · Jul 21, 2021

Dealer says no outstanding recalls/TSBs.

TSB 16-003 was done, that was some time ago. Of course my Rexxer reflash will have obviated that.

No TSB for the TPS for this bike, although 16-003 deals with "idle management".

gatdammit · Jul 22, 2021

Do you still have the emissions canister on? Pipe and air filter mods with Rexxer flash?

Mine doesn't stall between shifts but it will occasionally stall or the idle will hunt low when I come to stop after a fast highway run. More commonly during summer heat.

Hyprdrv · Jul 22, 2021

Bike is fully stock except Rexxer.

I don't recall if it stalled while on the stock ECU map.

I removed the emissions canister yesterday, and it still stalled once. So no joy there.

So far it seems it has no issues until / unless it is fully warmed up. I'm guessing the idle is higher when warming up.

It was cooler yesterday, about 25°C/77°F. Previously all stalls occurred at higher temperatures.

Irritating issue. I expected better from this bike.

Any way to reliably bump the idle 200 RPM without the bike eventually compensating for it?

gatdammit · Jul 23, 2021

Was your Rexxer tune specifically for a stock setup? Most of the base tunes are for increased intake flow and at least a slip on. The crappy OEM map is super lean at low RPM/ idle so the piggy backs or flash tunes generally make the mixture richer down low. If you didn't free up the flow, this could be the issue.

It's EFI, so no manual way to adjust idle.

Hyprdrv · Jul 23, 2021

Rexxer said to download the stock data, send it, and they would send an updated version. So that's what I did.

I don't know what they did. I don't know these bikes, so I didn't specify what changes to make. I just told them the results I needed.

They knew the bike was bone stock, and I told them I specifically wanted to smooth out the throttle, reduce the aggressive engine braking and improve the off-idle response (where the bike takes more than expected throttle to get going). The first two worked, the last one not so much.

They've expressed confidence the stalling is not due to the new map.

I've asked and there is no ECU mod to bump the idle up or disable the emissions recirculation valve.

I don't know if that's because the ECU code is still mostly opaque / unavailable, or because us owners are an unimaginative lot.

I can see no mod for the canister valve, since that valve might not exist on bikes earlier than 2016. Plus most would just remove the canister and plug the hose, which is free.

But it seems to me having the ability to move the idle up and down a few hundred RPM would be nice, and doing it via the settings menu would be even better. I'm surprised nobody has developed such a mod.

I was reading an interesting thread where the 950 owners had some crap gunking up their throttle bodies.

I kind of doubt that affects the 821/939s, but does anyone know for sure?

I'm going to try some new gas and reset the TPS and adaptives (again) because I don't know what else I can try before I leave for my trip tomorrow.

The bike was cold when I did the first TPS reset, which (to my understanding) is the right way to do it. But it's worth a shot.

When I get back from my trip, I will try to find some time to revert back to the stock map to see if that changes anything.

gatdammit · Jul 23, 2021

Carbureted vehicles were the only times I was constantly playing with idle speed. I think the theory is the ECU uses all it's data to maintain optimal idle...probably some emissions reasons in there too.

I can tell you two specific issues I had that affected idle/ stalling and excessive engine breaking. First was my cracked rear down pipe. It was probably cracked when I noticed a lot of hunting at idle after highway runs and occasional stalling. More prominent when it was hot out. Second was a broken secondary air circulation line on the bottom of the airbox. It was running like ****, got horrible mileage (like 10-15% loss) and the engine breaking was brutal. I **** canned the entire secondary air system (cheap blocker plates and bypass plug), which may have helped with engine breaking but I fixed the down pipe at the same time. Feel fairly normal. This motor engine breaks much more than an I-4, which I kinda like as I don't ride the breaks very much.

I have 23K miles and have seen my throttle bodies recently. They were fine. You can try the full Sea Foam treatment (google) if you don't want to pull the tank and air box to inspect the throttle bodies.

Curious - how did you reset your TPS? Like, a DIY method?

Hyprdrv · Jul 23, 2021

Nope, no magic. I'm too dumb for that.

The Rexxer User unit allows for TPS reset and clearing the adaptives. Apparently these are both required after reprogramming the ECU.

Thanks for the info, that helps. Mine is not noticeably hunting (yet), but time will tell.

I will definitely be looking up the Sea Foam TB cleaner process - although I suspect it involves removing the air filter, which means removing the tank, which may be beyond my skill set. If I had a place to work on the bike over the winter, I might tackle it, but I currently don't.

gatdammit · Jul 23, 2021

Pulling the tank is a *****. And R/R the airbox is worse. They hung a lot of somewhat fragile leads, lines and sensor stacks on the bottom of the airbox, which literally takes all my 190 lbs to force back on the TB stacks. Couple that with I'm a bit fat handed when it comes to delicate work and I've broken lots of stuff doing these jobs many times. But, if you plan to get intimate with her and do more than very basic maintenance or upgrades, it's good to be familiar with the process.

Project Farm on did a thorough test on the Sea Foam treatment claims. It works. I've sworn by the stuff for a very long time. Throw a bottle in all my tanks after oil changes. Did the intake and oil treatments on a couple cars.

Hyprdrv · Jul 23, 2021

Sooo.. which are you recommending first? Throttle body, oil, or gas?

gatdammit · Jul 23, 2021

Well, you can drop a can of the fuel treatment anytime. Have to do the oil treatment right before an oil change since you dump it after, IIRC. The intake takes the aerosol stuff they make and honestly, not quite sure you can do it on our bike unless you hooked the tank back up. For a car, you removed a vacuum line from the TB and shot it through that. But, I would group them all together like this:
1. Oil (preferably at normal interval). Put fresh stuff in after.
2. Intake, if possible.
3. Fuel, when she's put back together.

Watch the Project Farm video on it. Tons of car pages on forums devoted to it.

gatdammit · Jul 23, 2021

Man, wish my RapidBike could reset the TPS. How does it work on the Rexxer? That that was just a hard coded ECU flash.

Hyprdrv · Jul 23, 2021

There's just a button on the screen that says "Reset TPS". It must know the factory command(s).

Same for adaptives, you just press a button and bam.

I'll take a screenshot if/when I pull it back out to re-reset the TPS.

It seems the Rexxer is limited to fuel mapping - no other mods available. Which I guess is surprising and not. I guess nobody has been able to really tinker with the code itself.

Not sure I'll bother with higher-octane gas since none is available for much of my tour route.

Interesting that you dump the Sea Foam oil treatment right after. I guess it's a cleaner, not a treatment per se.

But yeah, I suspect doing the intake cleaning on our bikes would be a real PITA.

Hyprdrv · Jul 23, 2021

I wonder if I could mess with the TPS signal, just a bit, to make the bike think the throttle was a little bit more closed than it really is. That might bump up the idle.

Yes, I know it might mess up the mapping. I'm only talking 1-2% here.

Purely theoretical, since I have no time to do this right now.

Stalling issue

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