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Author Topic: 2013 GT250R EFI Is sputtering at low rev range when hot  (Read 3965 times)

dextrous

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2013 GT250R EFI Is sputtering at low rev range when hot
« on: March 20, 2015, 12:51:17 AM »

Hi Guys. Got a 2013 GT250R EFI model with the stock Delphi ECU. It has 12k on the clock.

Until a few weeks ago all was fine. One very hot day I went on a long ride and half way through, when in low rev range, the engine starts to sputter and seemingly skip a cylinder. It was bad, would almost stall at the lights and took a bit of heavy throttling to maintain both cylinders firing. Once at around 5k rpm the bike would run fine. This would only happen when the bike was warmed up. Only when I slowed down then tried to take off again it would sputter in the 2k-5k rev range.

Also, when it's idling the revs will jump from 1700rpm to 2000rpm. It used to be a constant 1800rpm (EFI - Cant change it).

So I did some research.

-I checked the voltage for the TPS. It was fine at 5V (manual says should be between 4.9 and 5.1. see pic: http://i.imgur.com/Pe0TBOr.png)
-My battery is 100% fine running around 14V at idle.
-I checked my plugs which looked fine.
-I didn't test voltage on my coils yet (should I?)
-I've checked the error codes for the bike which return NoEr (no error). Strange. Let me remind you also the delphi ECU's have a memory system that 'remembers' error codes even when the bike is turned off. So definitely no errors reported by ECU.
-I ran through some throttle body/injector cleaner into my tank. I'm about half way through that tank and still no signs of things getting better.
-My airbox was removed and looked for cracks, all seems fine.



Anyone have any [home] ideas I can try before I take it to a mechanic?

Just keep in mind, the bike runs fine when cold, and runs fine above 5k rpms. I am sort of stumped at what this could be as I know EFI's don't even have a fuel pump that can be serviced per chance it was getting clogged or something, and if the bike runs well over 5k rpm, I cant see why coils would be bad. Maybe I need my ECU updated?

Any other ideas?


Thanks folks.





« Last Edit: March 20, 2015, 01:17:16 AM by dextrous »
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Hylife

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #1 on: March 20, 2015, 04:15:42 AM »

Quote
...I checked the voltage for the TPS. It was fine at 5V (manual says should be between 4.9 and 5.1. see pic

You have done the wrong check on your TPS. It is the output voltage that you need to check, not the input supply voltage.

The TPS is simply a sealed potentiometer (like the volume knob on your radio). The carbon tracks do wear out and cause the output voltage to shift which is most noticable at idle.
For the anal amongst us, it is serviceable, sort of, instead of replacing it. The plastic heat sealed cover can be prised off and the internals can be given a liberal spray of electonics lubricant (NOT WD or CRC spray).

The output voltage (along with the EGO, and a couple of other sensors) set the injector open duration times. If the revs are hunting up and down at idle then the output voltage is too high.
Higher voltage = longer injector open time (like opening the throttle), but, at idle there is insufficient air so unburnt fuel exits the exhaust. Then the EGO sensor tells the ECU to shorten the injector open times. The air:fuel mix is corrected by the ECU and the whole system repeats this scenario over and over and your revs hunt up and down.

Quote
I've checked the error codes for the bike which return NoEr (no error).
Of course, there is often no error because an error code is only generated if a sensor feeds an "out of spec" reading to the ECU over a certain time period.

Quote
I didn't test voltage on my coils yet (should I?)

I would certainly check the condition of the HT leads and plug caps.
Coils are notoriously difficult to get a reliable test measurement from if the fault is only appearant at certain revs.
If you do replace the coils, I recommend you also replace the HT leads and caps as a standard process.
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dextrous

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #2 on: March 20, 2015, 05:08:53 AM »

Thanks for clearing up the TPS stuff Hylife! How do I test the voltage of the TPS then? Where should I put the positive probe?

Heres the image showing how: http://i.imgur.com/xPTkgoi.png , but the TPS has to be connected right? . do I just dig the positive probe into the A and C terminals until they protrude past the plastic wire insulation into the actual wire, or what?

Thanks :)
« Last Edit: March 20, 2015, 07:06:37 AM by dextrous »
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dextrous

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #3 on: March 21, 2015, 07:38:42 AM »

Figured it out. Wasnt getting any output voltage from the TPS. so I took it off, gave it a clean with electronics lube as you said (Thanks so much) and its fcking working!!!!! It idles at about 1800-1900RPM but that's fine with mee.

No more problems in the short ride I just took. We'll see down the line though! I am sure it was the TPS that was giving me issues though, so thanks so much mate.
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dextrous

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #4 on: March 22, 2015, 11:37:33 AM »

New update: Bike is not actually fixed. Nothings changed actually. Went on a longer ride and problem still persists.
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umop-ǝpisdn

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #5 on: March 22, 2015, 12:04:10 PM »

What fuel do you use?

Also, how long since the last service?

High idle + hot may possibly = lean burn scenario.

Vacuum leak, else an extremely dirty air filter may cause this.

Vacuum leak can be easily diagnosed using some starting spray, such as Aerostart. Spray stuff around the rubber joins and see if the idle speed changes.

Get eyes on the air filter and the snorkel to check for obstruction and filter cleanliness.
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dextrous

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #6 on: March 24, 2015, 09:16:32 AM »

Serviced 200km ago. Did oil (10w40) and oil filter and air cleaned air filter. Don't get why this is only happening when engine is hot.

Disassembled the whole air intake and inspected for cracks, blocks, etc.. all seemed good.
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umop-ǝpisdn

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #7 on: March 24, 2015, 08:31:14 PM »

The advantage of using an ether spray while the bike is idling, is that it checks for vacuum leaks that are less obvious.

Again, what fuel do you use? High octane fuels work badly in motorcycles.

Does the spluttering only happen at steady throttle (may indicate an ignition issue), while decelerating (may indicate an exhaust leak) or does it happen as you start to accelerate (lean burn scenario)?
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I used to be a sensitive, new age guy, but times have changed and now I am more of a caring, understanding, ninties type.

dextrous

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #8 on: March 24, 2015, 10:57:50 PM »

Use standard unleaded 91.

Sputtering happens during acceleration and from memory it backfires a bit on deceleration too. (only when bike is hot)

Also my idle is jumping from 1800rpm down to 1500rpm when stopped (only when bike is hot) .

Could it have anything to do with the oil I used? 10w40 from the motorcycle section of auto shop.
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hitz

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Re: 2013 GT250R EFI Is sputtering at low rev range when hot
« Reply #9 on: March 25, 2015, 04:50:25 AM »

My GT250R also having the same problems as your even thou I've change the plug cap and spark plug.
Above 5k rpm is running fine but below that the problems appear.

Is there any solution yet?

Thanks.
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