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Engine dying when coming to a stop


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OK I moved this to a new thread so I wouldn't hijack some else's.😐  To recap my VFR was dying most of the time whenever I came to a stop at red lights or stop signs and occasionally just decelerating into a tight turn.  It would always start right back up no prob but the same would repeat at the next stop.  Idle is where it's supposed to be, new fuel pump, cleaned and balanced injectors. plus I could find no loose vacuum lines or loose connectors.  To me the simplest and easiest troubleshooting was to unplug the Power Commander III and see what's up.  I did exactly that and took it for test ride #1 this afternoon and could not get the bike to repeat the problem. Hmmm.  I will repeat test ride tomorrow to be sure but so far it is looking like the PCIII may have been the culprit.  So my question is does that mean the PCIII was defective or could it have just been a bad map?  I have  zero experience with the PCIII's but have found an online manual @ DynoJet's website.  Also another question is does the bike even need this PC?  It is my understanding that the stock ECM is pretty capable of adjusting to changes such as my Two Brother's Pipes.  Does the PCIII actually improve HP, Torque, or MPG?  Or does it just give you controllability?  Thanks for any advice or sharing experiences with this.

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Did you remove the throttle bodies recently for some work? And did it do this before fitting the PC3?

Sent from my ONEPLUS A5000 using Tapatalk

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Know nothing about a PCIII but I have read where there have been running issues caused by bad Grounds for the PC. So have a good look at the wiring for it and make sure both power and ground wires have good solid connections. At least you've identified the culprit to your engine dying issues.

Cheers.:beer:

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Bike ran perfectly fine when it left showroom floor. There is no reason it shouldn't now if maintained in good condition.

 

It's air-flow mass that determines power and fuel & ignition needs to match for optimum output. With your mods, there is absolutely zero reason to have PCIII on your bike. Only needed if you've got extreme mods that factory ECU cannot adjust for. Such as big-bore high-comp pistons on stroker crank, larger valves with fully-radiused seats, D-ported intake-tracts, turbo or supercharger.

 

If you've got driveability problem, it's most likely maintenance issue. Worn plugs, cracked plug wires, dirty injectors, clogged fuel-filter or sock screen. This causes issue with spark and fuel. Using PC to try and compensate is not solution. Proper troubleshooting with testing and measurements to find faulty or misadjusted components is correct procedure. Followed by replacing worn-out faulty part and re-adjustments. Mis-adjusted TPS sensor and idle-switch is very common culprit.

 

In this case, very common for PC to cause more problems than it helps. Restore bike back to factory-fresh clean condition and it'll run perfect like when it left showroom floor. You're halfway there with disconnecting PCIII, now remove it completely and you've solved problem for good.

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OK after second test ride the issue has completely disappeared so obviously it WAS the PCIII. So since I am removing the PCIII I'm guessing I need to remove the O2 eliminators as well?

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no. you can leave those alone for now. Make only one change at a time.

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Had a similar problem with my 06 and a PC3. Turned out it was that where I had the PC3 located, which was in the space just behind the rear brake fluid reservoir shown in red. My sergeant seat had a tab on the underside that pressed on the PC3 when I sat squarely on it, like when stopped at a light, and it would start to misfire from then on. Went through all types of troubleshooting until I noticed the indentation on the PC3. I shifted the position of the PC3 to avoid the tab and has been working perfectly ever since.

 

 

PC3 space.JPG

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I had a similar problem with my VFR.  But I have a Bazzaz Zfi installed.

 

Whilst the Bazzaz was installed properly, according to the instructions, I really hate the use of scotchlocks.  They might work for a while, but in the end - in my experience, they just result in bad connections.  I traced it to the fact that the scotchlock that was connected to the switched power lead was dodgy.  I removed it and soldered the wire instead.  Then went around and removed the other scotchlocks that were used with the Bazzaz Zfi and haven't had any problems since then.

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  • 2 months later...

Update:  After removing the Power Commander 3 and the problem disappearing, it began to resurface 3 or 4 days later.  I started keeping track of when this problem would occur and under what conditions.  It took quite a while but suddenly one day I had an AHA moment. I knew the culprit.  But to be sure I started predicting when it would occur and when it wouldn't.  And I was right every time.  It is a fuel pickup problem happening inside the gas tank.  Only when I have 1/3 of a tank or less and as I come to a stop the remaining fuel is thrown forward to the front of the tank -- away from the fuel pump and its pickup --  and the injectors are starved of fuel and the engines dies.  After coming to a complete stop the remaining fuel in the tank sloshes back and levels out and the pickup can get fuel again.  The bike restarts easily, idles fine, and accelerates like a demon.  Until I come to a stop again and the problem reoccurs.  Fill the tank up and the problem completely disappears until it gets back to the 1/3 full level and it all starts over.  Removing the PC3 fooled me because I filled the tank up at the same time making the problem disappear.  I broke the cardinal rule of troubleshooting and made 2 changes at once.🙁.  So then after taking it to the dealership to let them confirm and possibly fix the problem they discovered that the tank etching and lining process to remedy 5 years of storage with bad fuel left in the tank did not take and is already beginning to bubble and separate  from the inside of the tank.  The rust damage was just too great.   Sooooo I've got to replace the tank.  ☹️.  I have located an '04 tank in pretty good shape for an excellent price (😉🙏 thanx Curt) and posted the question of fitment to my '05 and (🙏 thanx to Cogswell) he has assured me that the fitment will be the same. 

As a side question,  is there anyone here who has seen the inside of these tanks and can tell me whether or not there are baffles welded into the bottom and/or sides?  That seems to me would prevent my problem from happening but maybe mine got rusted out during the 5 years of storage?  As far as I can tell there is no way to change the height or level of the fuel pickup to fix the problem so I am hoping that just replacing the tank will solve my problem.  If anyone knows different please inform me and have my gratitude for the education of a VFR dummy. 🤪

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4li3nvfr

 

No baffles in the tank. It’s an unusual fault as the last time I replaced my pump the pick up is right at the bottom of the pump near the tank bottom and located inside, what I would call an aluminium scrubbing pad. There is also a very fine screen filter fitted on the inlet as well. There is a rubber hose that connects the main filter and this could have a hole in it. Apart from that the pump is securely fitted to the assembly so movement of the pickup would be strange.
 

Does your fuel gauge indicate correctly as it could be that the float has been bent and although it says you are at 1/3 full it could be you are almost empty, hence fuel starvation?

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That is a possibility but I doubt it because I can continue riding for another 40 or 50 miles or so without running out.  The problem may be the fact that this is a replacement non-OEM fuel pump.  Maybe the fuel pickup mounts differently to it and is raised up a little too  high?  I have not personally laid eyes on this because my local Honda shop has done the work.  I will ask them about it.  Thanks for the info.

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12 hours ago, 4li3nVFR said:

That is a possibility but I doubt it because I can continue riding for another 40 or 50 miles or so without running out.  The problem may be the fact that this is a replacement non-OEM fuel pump.  Maybe the fuel pickup mounts differently to it and is raised up a little too  high?  I have not personally laid eyes on this because my local Honda shop has done the work.  I will ask them about it.  Thanks for the info.

Think you are onto it, especially as you have a non oem pump. I wonder if the whole assembly has been replaced or only the pump? 

Attached is the fuel pump description taken from the 5gen Service Manual, I'm sure the 6gen won't be too different. It specifically states the pickup is within its own tank to prevent the issues you've had. Perhaps this tank is missing around your mesh filter.

 

IMG_1127.PNG

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12 hours ago, 4li3nVFR said:

Awesome!  Thank you Grum for the pic and text.  That definitely helps me see what is going on in there. I'm gonna show it to the Honda guys in case they don't have it.

Here's a view from the 2005 6gen parts list, item 6 shows the rubber tank arrangement for the fuel pickup.

 

20210729_225510.jpg

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