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Batgirl

Decel pop and cold start stutters

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I have recently developed an issue with the bike not wanting to run smoothly at first start up (usually takes about 10 minutes of warm up) and very loud decel pops.  The cold start issue started last year and I thought it was just because we were in the mountains but it has started to be a regular occurrence, even at home.  The issue is after starting the bike, if I don't let it warm up for about 10 minutes, it will feel like it is shutting off at random intervals.  Once it warms up, it runs smoothly but that first 10 minutes almost feels like a TPS issue in a vehicle.  The decel pops just started today.  Very loud, almost sounds like gunshots when I let off throttle or shift gears.  

The bike is a 2015 with an ECU flash from 2WDW and a Mivv exhaust system.  

My bf (who wanted me to get Ivan to flash the ECU) says that it is all probably related to the flash and I should get it redone.  I have no idea what it is.  Checking the diagnostics, there are no codes.  

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Posted (edited)

How many miles?  Maintenance history?

Decel pop can be a couple things: exhaust gaskets/leaks, intake leak, or too much or too little fuel when the throttle is closed. 

I think you may have 2 different things going on that may or may not be related. 

If the bike ran fine initially after the exhaust and flash were installed, and now doesn’t - then it’s likely not related. If you’ve moved to a lower elevation and had it flashed for your old elevation, then a reflash would make sense as the baro pressure sensor can only adjust the fueling by so much depending on elevation. 

-Skip

Edited by skipperT
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20 minutes ago, skipperT said:

How many miles?  Maintenance  history?

Decel pop can be a couple things: exhaust gaskets/leaks, intake leak, or too much or too little fuel when the throttle is closed. 

I think you may have 2 different things going on that may or may not be related. 

-Skip

It has 8500 miles.  I have changed the oil at the start of every riding season. I changed the air filter last year.   I synced the throttle body last year.  Other than that, nothing maintenance wise.

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2 hours ago, Batgirl said:

I have recently developed an issue with the bike not wanting to run smoothly at first start up (usually takes about 10 minutes of warm up) and very loud decel pops.  The cold start issue started last year and I thought it was just because we were in the mountains but it has started to be a regular occurrence, even at home.  The issue is after starting the bike, if I don't let it warm up for about 10 minutes, it will feel like it is shutting off at random intervals.  Once it warms up, it runs smoothly but that first 10 minutes almost feels like a TPS issue in a vehicle.  The decel pops just started today.  Very loud, almost sounds like gunshots when I let off throttle or shift gears.  

The bike is a 2015 with an ECU flash from 2WDW and a Mivv exhaust system.  

My bf (who wanted me to get Ivan to flash the ECU) says that it is all probably related to the flash and I should get it redone.  I have no idea what it is.  Checking the diagnostics, there are no codes.  

Did the cold-start issue begin right when you got the ECU flashed?  

I agree with @skipperT - it could potentially be an air leak somewhere.  The fuel map within the ECU flash doesn't change or gradually go bad, something else has changed.

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***2015 Candy Red FJ-09***

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9 minutes ago, betoney said:

Did the cold-start issue begin right when you got the ECU flashed?  

I agree with @skipperT - it could potentially be an air leak somewhere.  The fuel map within the ECU flash doesn't change or gradually go bad, something else has changed.

Not immediately, but not terrible long after (within a few months).  I didn't think it would change, but he keeps on about it so I said I would ask around.  He keeps saying that there should have been updates done, etc and I should let him send it to Ivan to be redone.  

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I'm skeptical it's the ECU flash, but not impossible. 

How's the O2 sensor? Has it come loose?

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'15 FJ09

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Posted (edited)

Possible the airbox breather hose is a bit twisted up... AIS hoses mixed up?...Airbox rubber boots on TBs not tight... I'm just thinking of all the things that get pulled off when the TBs get synch... 

The weird start and the fact it starts better after riding for about 10mins reminds me of when I didn't notice my airbox breather hose was twisted up... You should hear the distinct airbox whine if breather hose is not kinked up... 

Edited by norcal616
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2012 wr250f - C-class 30+ age group
2015 fz-07- Hordpower Edition-80whp
2015 fj-09- Graves Exhaust w/Woolich tune by 2WDW @120whp

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Posted (edited)

As NorCal mentioned, double check the things you may have touched or bumped when the sync was performed. Also depending on how the caps covering the throttle body ports were removed, one of the rubber nipple doo-dads could be torn depending on how you removed them (pliers can be brutal). Or if those weren’t removed, perhaps a line is open, maybe leading to the IAP sensor. The crankcase breather line being kinked or not connected properly could cause some weird things too. Same with a twisted fuel line, or one of the tank drain lines that hook into the bottom of the fuel tank. If those vents are kinked and blocked it can cause the fuel pump to have difficulty providing the correct pressure into the fuel rail.

a loose o2 sensor in that exhaust could also cause it, as Koth442 mentioned. Another poster had a bad weld seam on his Yosh pipe which can introduce air into the system where the ECM doesn’t expect it. Ultimately causing a running problem.  

I’d pull it apart and double check all of these things. You really shouldn’t need to idle the engine longer than 30 seconds before riding away without any drama. Good luck, and keep us posted. 

I’d backburner the “bad flash” idea for now until you 100% know the rest of the bike is ok.

-Skip

 

Edited by skipperT
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12 hours ago, koth442 said:

I'm skeptical it's the ECU flash, but not impossible. 

How's the O2 sensor? Has it come loose?

I will be checking that when I get home from work.  

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12 hours ago, norcal616 said:

Possible the airbox breather hose is a bit twisted up... AIS hoses mixed up?...Airbox rubber boots on TBs not tight... I'm just thinking of all the things that get pulled off when the TBs get synch... 

The weird start and the fact it starts better after riding for about 10mins reminds me of when I didn't notice my airbox breather hose was twisted up... You should hear the distinct airbox whine if breather hose is not kinked up... 

I will check this also.  I don't remember hearing the whine, so that may be something.  

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9 hours ago, skipperT said:

As NorCal mentioned, double check the things you may have touched or bumped when the sync was performed. Also depending on how the caps covering the throttle body ports were removed, one of the rubber nipple doo-dads could be torn depending on how you removed them (pliers can be brutal). Or if those weren’t removed, perhaps a line is open, maybe leading to the IAP sensor. The crankcase breather line being kinked or not connected properly could cause some weird things too. Same with a twisted fuel line, or one of the tank drain lines that hook into the bottom of the fuel tank. If those vents are kinked and blocked it can cause the fuel pump to have difficulty providing the correct pressure into the fuel rail.

a loose o2 sensor in that exhaust could also cause it, as Koth442 mentioned. Another poster had a bad weld seam on his Yosh pipe which can introduce air into the system where the ECM doesn’t expect it. Ultimately causing a running problem.  

I’d pull it apart and double check all of these things. You really shouldn’t need to idle the engine longer than 30 seconds before riding away without any drama. Good luck, and keep us posted. 

I’d backburner the “bad flash” idea for now until you 100% know the rest of the bike is ok.

-Skip

 

Exhaust will be thoroughly checked tonight also.  Making sure everything is tight and not kinked or twisted.  

I think the flash is fine (bf just wants to prove he was right and I was wrong for not going with Ivan).  

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Thank you all for the ideas.  When I get home from work I will be checking all of these out.  I will update if I find anything.  

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To put the bad flash idea to rest...

Is there another FJ you can swap ECUs with?  Just replace yours with another and ride and you'll quickly have an answer to that question.

cb


1968 Triumph Bonneville 650
1971 Norton Commando Roadster
2002 Harley 1200 Sportster
2003 Honda ST 1300
2016 FJ 09

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13 hours ago, nhchris said:

To put the bad flash idea to rest...

Is there another FJ you can swap ECUs with?  Just replace yours with another and ride and you'll quickly have an answer to that question.

cb

Not another one that I know of. 

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1 exhaust bolt was loose and the muffler portion had slipped a slight bit.  No chance to test ride due to weather. I will update as soon as I test ride. 

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