Unstable rpms

[bobrx3]

If I warm warm up the RX3 and then try to hold a steady rpm (say 4000rpm or 5000rpm) with the bike in neutral, I don't seem to be able to do it. With a constant throttle opening (no motion of the grip) the rpm bounces around. At 5000 rpm it might dip as low as an indicated 4800 and kick high to maybe 5200 and you can hear and feel slight changes in running speed. I can feel this when riding with a very light throttle (holding a steady speed on a flat road). Otherwise the bike runs fine. Accelerates without hesitation or stumbling. As long as I'm speeding up, slowing down or there's a load on the bike (uphill) it feels fine. The bike has only stalled one time at idle, a hundred miles or more ago.

I don't think it started out like this (though maybe I just didn't notice it). I'm at 500 miles. I just did a valve check. It was doing this before the check and the valves were about 0.1mm (wide). I brought them back into spec (0.06mm) and it's still doing it. Resetting the valves seemed to make no difference. I haven't look at the air filter or fuel filter, but at 500 mostly dust free miles neither is likely to be the problem. I don't have a spare plug to swap in, though I do have one on order. I was noticing it on my last tank of gas as well as the current one (bought from different places), so I doubt dirty gas is the problem.

If it had started after I had pulled the tank and adjusted the valves I'd think it was something I'd done, but I'd noticed it before and was hoping the valve adjustment would fix it, but it didn't.

Is anyone else seeing anything like this? I know there have been stalling issues reported and this could be related, but I'm really not seeing stalling.

Before I go digging around in the FI system I just want to make sure that this isn't a characteristic of the RX3 (I can't believe it is, but it doesn't hurt to check). The malfunction indicator light is off and there are no stored error codes.

It could be almost anything. A TPS problem, an injector problem, a fuel pump pressure issue, a CDI issue and so on. I will be contacting CSC on Monday to see what they have to say before digging into the bike, but I'd welcome comments from others who have (or who haven't) experienced similar behavior.

[SpudRider]

Welcome to these forums; we are glad you joined us.

My RX3 holds a steady rpm while idling, and while riding. However, I haven't tried to hold a higher, steady rpm using more throttle, while idling. I will conduct this experiment sometime later this week.

[katflap]

I have only noticed a very slight surge effect when riding at about 30 MPH @4000 RPM under a neutral load.

I don't think the effect was enough to even register on the Tacho.

I will have a play at 5000rpm on my way to work tomorrow, see if I get anything.

I think the ECU kicks in to "closed loop" when under a static RPM or neutral load, which uses the O2 sensor for feed back. But I'm just guessing at where the problem could be.

[bobrx3]

Thanks for the comments. The slight surging I feel under similar conditions - " riding at about 30 MPH @4000 RPM under a neutral load" doesn't really register on my tach either. The surging seems no worse (in fact it's better) then I used to feel with my V-Strom 650. The rpm fluctuation only really shows up well with the bike in neutral (which is absolutely no load). I'd guess that under riding conditions at neutral load, any surge would create a load and would tend to be slightly suppressed.

I'm also not sure about how sensitive the tach is. When I put a digital tach on there I see fluctuations even when the analog tach looks rock steady (almost like the needle sometimes sticks slightly). Could be mechanical or could be the software they're using to drive the tach.

I'd really like to take a look at the engine parameters while the rpms are not steady. The signals from the TPS, MAP, O2 sensor etc. but I don't have any diagnostics working yet. I've been looking at using a OBDC with bluetooth wired to relevant diagnostic port pins (+v, Gnd, and K-line) but I don't get any data using the Torque app on my Android phone (works fine with my car). I have the Delphi PCHUD software but no hardware connection for it yet. Build or try to buy from China I guess.

[Jay In Milpitas]

Hi Bob,
just pondering your condition, but I'm a novice with EFI so I may be way off track.

Since the O2 sensor senses O2 level in the exhaust stream, have you checked your exhaust pipe flange and the clamp to the muffler for tightness? I haven't noticed if my bike is flippity floppulating under steady throttle, but I had been getting a bit of exhaust popping on deceleration lately, and found those 3 fasteners less than tight. Snugged them all up and no populociousness any more. Wondering if loose head pipe vibrating at certain rpm's could make the controlly box thing think it needs to change the signal to the squirty part?

Have you changed brands of fuel recently? I know that here in the Republik of Kalifornia ARCO has a higher percentage of alcohol (methanol) in their fuel. One of my trucks wouldn't run for beans with it in the tank.

One time after adjusting my valves I had an occasional, sporadic problem with the fuel pump quitting then resuming, manifested by the engine dying and restarting. Under close examination I finally noticed the lock tab on the electrical connector to the pump was touching one of the little bolt heads, preventing the tab from locking as well as not letting the connector fully seat. A couple light passes with a round file on that area of the lock tab solved the problem. Don't know why I hadn't noticed it before.

Good luck in your quest.
Jay

[bobrx3]

Under close examination I finally noticed the lock tab on the electrical connector to the pump was touching one of the little bolt heads

I know exactly the connector to the pump that you mean. There's a bolt that gets in the way of the locking tab. I noticed it taking the connector apart, so I made a special note to check it when I reconnected it. Looks like it must be a common issue!

Headers and pipe connections are tight, so it's not that, but it's an interesting idea to maybe disconnect the O2 sensor and so make the system run open loop. It could be closed loop on partial throttle and open loop on WOT but I don't think that info has ever been provided. That's typically the way these things work though. I know the engine will still run with it disconnected but I haven't checked if it makes any difference to idle or higher rpm stability.

The other sensors aren't part of any feedback loop, so they shouldn't cause instability unless they are generating a noisy signal rather than a constant voltage. I think they are probably required for the engine to run though. Easiest way to measure them would be via the diagnostic port, but the signals could be monitored on an oscilloscope or even using a voltmeter once you can actually get to the appropriate wires.

All the fuel here is the typical 10% ethanol - or at least that's what the pumps claim. I've heard rumors that there's a marina with alcohol-free gas for boats not far from here. More expensive of course but it might be interesting to try.

I'm still hopeful of being able to connect to the diagnostic port. That's really the best way to look at this. If I can't get my system to work I'll have to talk with CSC about getting one on loan for a few days.

Most of all I'm looking for feedback on whether other RX3s do this. If they all do it it's probably a waste of time trying to eliminate it and it could just be a characteristic of this engine.

[Weldangrind]

Originally Posted by Jay In Milpitas

I haven't noticed if my bike is flippity floppulating under steady throttle, but I had been getting a bit of exhaust popping on deceleration lately, and found those 3 fasteners less than tight. Snugged them all up and no populociousness any more. Wondering if loose head pipe vibrating at certain rpm's could make the controlly box thing think it needs to change the signal to the squirty part?

That's one of the funniest posts I've read in awhile.

[katflap]

Hi Bob,
Tested @ 5000 RPM riding, Neutral load , all fine.

Tested @ 5000 RPM Stationary, fine also, just a little tacho needle vibration. No surging.

Also did 40000 RPM @ £30MPH, as stated in my previous post, no surging here either, so i dont know where i got that from.

Regarding data cables, i know some guys in china managed to wire up a regular cable and got it to work.

For myself, i got a dedicated cable from Taobao via Taobaotrends.com agent (see spuds excellent tutorial )

Though it is bit pricey

https://item.taobao.com/item.htm?id=39520023502

The cable cost $37.70 (£24)

It weighs 0.23Kg

I had mine shipped with some other stuff but if i have worked it out correctly,
i think you could get it mailed for about $6.00 using China or HK post with tracking.

[woodlandsprite]

Originally Posted by Weldangrind

That's one of the funniest posts I've read in awhile.

I agree

[SpudRider]

Originally Posted by Jay In Milpitas

...I haven't noticed if my bike is flippity floppulating under steady throttle, but I had been getting a bit of exhaust popping on deceleration lately, and found those 3 fasteners less than tight. Snugged them all up and no populociousness any more. Wondering if loose head pipe vibrating at certain rpm's could make the controlly box thing think it needs to change the signal to the squirty part?...

Originally Posted by Weldangrind

That's one of the funniest posts I've read in awhile.

Originally Posted by woodlandsprite

I agree

X3.

[SpudRider]

Originally Posted by katflap

Hi Bob,
Tested @ 5000 RPM riding, Neutral load , all fine.

Tested @ 5000 RPM Stationary, fine also, just a little tacho needle vibration. No surging.

Also did 40000 RPM @ £30MPH, as stated in my previous post, no surging here either, so i dont know where i got that from.

Regarding data cables, i know some guys in china managed to wire up a regular cable and got it to work.

For myself, i got a dedicated cable from Taobao via Taobaotrends.com agent (see spuds excellent tutorial )

Though it is bit pricey

https://item.taobao.com/item.htm?id=39520023502

The cable cost $37.70 (£24)

It weighs 0.23Kg

I had mine shipped with some other stuff but if i have worked it out correctly,
i think you could get it mailed for about $6.00 using China or HK post with tracking.

As always, thanks for your detailed report, and your willingness to help, Kat.

[bobrx3]

Thanks Katflap. It's useful info that your bike doesn't seem to do what mine is doing.

I've read your excellent write up on diagnostics. You did a lot of work on that!

Getting the cable via TaoBao looks like a lot of work so I've ordered on of the VW VAG-COM cables. As far as I can tell it's probably a K-line to RS-232 level converter and serial to USB interface so I should be able to talk to it via PCHUD over a com port (assuming I can get it to install in the COM1 to COM4 range). Interfacing to the diagnostic port on the RX3 should be easy as there are only three active wires (+v, Gnd and the K-line). I can a VAG-COM adapter in the US for $6 and it will be here in a few days. Not much lost of it doesn't work!

I have your PCHUD files and a second version of PCHUD I downloaded from a Russian website. Seems to load OK on my XP laptop.

The bluetooth ELM327 interface I have doesn't seem to want to talk to the MT05 on the RX3. I wired it up the the appropriate pins and it powers up OK but I can't get it to talk to me using generic ELM 327 software. Probably doesn't speak proper MT05 language, which may be different from that used in most cars? Even if I could I'm not sure I could easily access all the engine parameters. Works fine on my K-line Subaru though.

I haven't talked with CSC yet, but I intend to give them a call this afternoon and see what they have to say.

[jct842]

On my majesty 400cc scooter it was impossible to hold it at 3000rpm with it on the center stand. Always would slow down or speed up, yet with the wheel on the ground and while riding you could hold 3000 rpm all day long. Seems it just needed a load on the engine. John

[bobrx3]

Thanks for the data point on the scooter. I guess it could be a characteristic of small displacement fuel injected engines with one (or two) cylinders. It's not something I've ever noticed on the carburated bikes I've owned and it's not something I've noticed on any fuel injected cars either.

I spoke with CSC yesterday and they said that they have seen this behavior and it's more noticeable on some bikes than others. It doesn't seem to be associated with any particular fault and running the engine diagnostics doesn't show any particular anomaly. It looks like it could be due to the cumulative effect of a number of small fluctuations. Sensors that may be slightly noisy, tiny intake or exhaust leaks, fluctuations in spark efficiency etc.

I guess what I'll do is to go through the engine checking all the sensor connections and maybe using some contact lubricant on them. I'll replace and maybe index the spark plug (probably with an iridium version), spray around the intake looking for leaks and oil and check the air filter. If all that makes no difference then I'll either live with it or dig into the signals from the sensors looking for noise.

[Adjuster]

I think a nice new NGK iridium plug is going to go a long way for you in smoothing out the bike. Get a couple extra to have on hand. I am obsessive about removing, cleaning and re installing my plug. Bike always runs better with a clean plug, does not need to be new, only cleaned. Be sure to report to us the condition of the plug you are currently running when you remove it.


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