Author Topic: Low throttle hesitation  (Read 7965 times)

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KTM_EnfieldRider

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on: March 25, 2014, 11:48:22 am
Greetings to everyone.  I am new to the forum, but have been gleaning some helpful points for a while.  I drive the G5 India-made Classic 500 EFI which I believe is close to the same bike with a few less sensors/safeties.  I am having some hesitation in idle-to-low throttle.  It almost feels like it's choking.  It never stalls, but it acts like it will.  Then after giving a little more throttle, it jerks back to normal acceleration.  I have noticed that she runs much better when she has a full tank of gas.  The less gas in the tank, the worse it gets.  Does anyone know the working pressure of the fuel pump?  The fuel pump sounds fine when ignition is turned on.  I have some mechanical ability, but this is my first fuel-injected bike.  Finding qualified mechanics with proper tools in Kathmandu has been unsuccessful.  Any suggestions?


High On Octane

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Reply #1 on: March 25, 2014, 12:18:48 pm
I haven't heard of too many fuel pump problems with the UCE bikes.  It seems like most who have suspected the fuel pump, it had turned out to be a different problem.  One known problem with the Indian made UCE models is that they do not use an oxygen sensor, which seems to cause issues like you are describing, in colder weather.

We need more information to help diagnose tho.  What part of the world do you live?  What elevation do you ride at?  Do you have major elevation changes while riding?  Does the problem occur when cold, hot, or all the time?  Does it only stumble off of idle, or does it stumble at any throttle position when the throttle is opened further?

Scottie J
2001 Harley Davidson Road King


Vince

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Reply #2 on: March 25, 2014, 04:24:35 pm
     Most likely you have some water in your gas, or you have a bad battery ground. I've had a couple of broken negative terminals that were sort of held together by the rubber cover. You can't see until you peel back the cover. Both problems will result in your symptoms.


barenekd

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Reply #3 on: March 25, 2014, 08:39:07 pm
The first thing to do is get rid of the Bosch plug and replace it with an NGK BPR6ES. That usually takes care of that type of problem.
Bare
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Arizoni

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Reply #4 on: March 25, 2014, 11:48:12 pm
KTM_EnfieldRider:

The fuel pump is regulated to produce a pressure of 294 KPa.  That is 2.940 Bar or 42.6 PSI.

Be very careful if you remove the rubber hose which is attached to the fuel pump. 
The plastic fitting is very fragile and if it is damaged the cost of a new fuel pump will almost put you in the poor house.

I don't see how the level of the fuel in the tank could be effecting the pumps output pressure or volume.
The increase in pressure at the bottom of the tank due to a increase in volume is almost nothing compared with the pumps output pressure.

You didn't say how old your RE is but I suspect the problem is either with the spark plug as mentioned above or with some form of buildup in the nozzle of the fuel injector.
My suggestion is for you to look at the available fuel injector cleaners used to clean automotive fuel injector systems.
In the USA, one of the best is Chevron Techron, a fuel additive put into the fuel tank.
There are several other brands and they all can clean the injector nozzle.

If you do try one of these automotive fuel injector cleaners remember, they are made for autos with large fuel tanks.  Read the instructions and figure out how much cleaner per gallon is needed and then add that much to your almost full fuel tank.

Personally, because of the risk of testing the fuel pump pressure and damaging the outlet, I would try the cleaner before messing with it.
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


KTM_EnfieldRider

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Reply #5 on: March 26, 2014, 06:07:59 pm
The bike is a 2013 C5 500cc EFI(not G5...sorry I misled on my first post).  It has about 10,000 KM (6200 Mi.).  The problem has been pretty much the same for the last 3,000 KM (4 months).  I live in Kathmandu, Nepal at an elevation of about 4500ft.  The primary plug I use is the NGK BPR6ES and secondary is still factory Bosch UR6DC.  A friend brought the NGK from the States because they are not sold here.  Is there an NGK cross for the UR6DC?  I wish I could get the Chevron Techron here, but I have been using the Gunk fuel injector cleaner the last couple of tanks.  I have cleaned the throttle body.  Fuel quality is, as you can imagine in a 3rd world country, pretty bad.  The plugs are covered with black carbon build up, but that seems to be a normal problem with the EFIs here and in India.  I put new plugs in, but it had no effect.  Cold/hot ambient and engine temps do not affect the problem.  It stumbles just above idle only.  I know the fuel tank scenario sounds irrelevant, but the problem does seem to disappear with a full tank of gas and reappear when it drops below a half tank.  The only other thing I have found is a broken vacuum line that runs from the filter box to what looks like a manifold block beside the battery.  I'm not sure how to check for a possible fault code, but the engine light's function is normal.  I haven't checked any wiring yet.  I guess that will be my next step.  Thanks for you input guys.  Keep it coming!


Arizoni

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Reply #6 on: March 26, 2014, 10:53:55 pm
To check the fault code, there is a single connection wire near the ECU that is to be grounded.  The MIL will then flash out the stored fault codes in a series of short and long blinks.

One problem with this is the ECU will flash out the codes of all of the faults it has ever recorded from day one.  The memory can't be cleared so if any exist, trying to figure out which one(s) are the right one(s) could be a problem.

Anyway, if the MIL light has never stayed turned on and stayed on there probably aren't any fault codes stored.

My G5 doesn't seem to have a vacuum line running from the air filter box to a manifold but I suppose any cracked tubes should be replaced.
While your messing around the filter area, you should knock out as much dirt as possible from the inside surfaces of the filter cartridge.  The air flows from the inside to the outside.  A better idea would be to just replace the filter if you haven't done that for a while.

One thing that can effect the air/fuel ratio is the TPS (Throttle Position Sensor).
If you have a volt/ohm meter you can check the voltage at different throttle settings.

Here's a link to Singhg5's post that tells how it's done.

http://www.enfieldmotorcycles.com/forum/index.php/topic,10309.msg119217.html#msg119217
Jim
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1999 Miata 10th Anniversary


KTM_EnfieldRider

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Reply #7 on: March 27, 2014, 03:32:01 pm
Thanks for the throttle sensor tip, Jim.  I pierced the blue wire, but I had to set my voltmeter to 300mv to get a reading.  With ignition switch on (engine not running), I am reading a range of only 0.1-1.4mV when I open and close the throttle.  What's your take on this?  It is a Fluke 73 III and I know its reading battery voltage correctly.  I went to the authorized repair shop here in Kathmandu to ask for the specs on that sensor.  They only have one service manual, and it was locked up in the supervisor's desk (who did not come to work today).  They said I could not order a service manual.  Except for throttle just above idle, the bike runs fine.  If the sensor were completely toast, would it run at all?  The vacuum line coming from the filter box is for clean air supply.  I replaced it when I found it was cracked.  The filter is in good shape, though I think the filter box design on the 500cc is ridiculous.  Thanks again. -Jason


gashousegorilla

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Reply #8 on: March 27, 2014, 08:08:02 pm
The bike is a 2013 C5 500cc EFI(not G5...sorry I misled on my first post).  It has about 10,000 KM (6200 Mi.).  The problem has been pretty much the same for the last 3,000 KM (4 months).  I live in Kathmandu, Nepal at an elevation of about 4500ft.  The primary plug I use is the NGK BPR6ES and secondary is still factory Bosch UR6DC.  A friend brought the NGK from the States because they are not sold here.  Is there an NGK cross for the UR6DC?  I wish I could get the Chevron Techron here, but I have been using the Gunk fuel injector cleaner the last couple of tanks.  I have cleaned the throttle body.  Fuel quality is, as you can imagine in a 3rd world country, pretty bad.  The plugs are covered with black carbon build up, but that seems to be a normal problem with the EFIs here and in India.  I put new plugs in, but it had no effect.  Cold/hot ambient and engine temps do not affect the problem.  It stumbles just above idle only.  I know the fuel tank scenario sounds irrelevant, but the problem does seem to disappear with a full tank of gas and reappear when it drops below a half tank.  The only other thing I have found is a broken vacuum line that runs from the filter box to what looks like a manifold block beside the battery.  I'm not sure how to check for a possible fault code, but the engine light's function is normal.  I haven't checked any wiring yet.  I guess that will be my next step.  Thanks for you input guys.  Keep it coming!



  Jason, if you are POSATIVE that this only happens when your fuel tank is Low... ... And with the less then ideal fuel supply you mention.  I suppose it may be possible, that the inlet screen on the fuel pump is starting to clog from the bottom up. Which could cause some fuel starvation,.... just a thought.

 As far as YOUR efi system. You mentioned that you are in Kathmandu. Do you have a Indian domestic bike, or a export model like we have here in the states? I mention this because evidently there are differences in the system. Particularly in regard to the TPS sensor..... or at least there was on the earlier bikes.


An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


Arizoni

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Reply #9 on: March 27, 2014, 10:14:25 pm
KTM
The TPS is capable of providing an output of 0-5 volts.
At idle speed the reading should be 0.6 +/- 0.2 volts

If you read thru Singhg5's link I gave above, you will see that he got readings of 0.75 volts at idle and 4.01 at WOT.

To give the system full operating voltage during the test, I suggest you start the engine before verifying the idle speed voltage output.
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


abstruse1

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Reply #10 on: March 30, 2014, 01:39:56 pm
I hope this isn't hijacking (if it is, keelhaul me!), but this topic brings up the obvious question, why not juts fit a good carb?  Lots cheaper than the Dyna ECM cheater box, easy to tune, etc.  The only downsides I can see have to do with large altitude changes and, maybe, fuel economy.
Abstruse1
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Roeland

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Reply #11 on: March 31, 2014, 10:50:18 am
Very interesting - with low fuel in the tank (Indian version) I also experience a little hesitation which quickly disappears with a blib of the throttle. I never made much out and usually just fill up.


KTM_EnfieldRider

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Reply #12 on: April 05, 2014, 04:19:14 pm
I rechecked the TPS voltage with the engine on...no reading.  Then I moved my black lead from the engine block to the negative post on the battery...bingo.  The voltage reading appears to work smoothly within the specs above.  So why am I not getting a good ground on my engine block?  The bike was sitting on concrete with the center stand.  Anyway, this puts me back at the drawing board.  I have taken some interest to the recent "Clogged Fuel Filter" posts.  When I get time, I'll check the filter.  I'll keep you guys posted.  The hesitation is definitely getting worse as the fuel level drops.  The fuel light has not come on yet.  However, lately it has stalled a few times just after starting the engine (with warm engine)and slightly working the throttle.  I know it is normal to have a short delay in response to a quick rev of the throttle.  But this hesitation is there in slow throttle movement just above idle.


High On Octane

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Reply #13 on: April 05, 2014, 04:43:52 pm
If you feel you are getting a bad ground on the block itself you might not be getting a good spark.  You could try running an extra ground wire from the battery ground directly to one of the bolts on the motor itself.  I have done this with cars in the past that had a weak idle and it cured it immediately.

Scottie J
2001 Harley Davidson Road King


ROVERMAN

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Reply #14 on: April 05, 2014, 09:39:33 pm
+1. There maybe an issue between the horribly inadequate battery and undersize wiring on our bikes. :o :o
Roverman.