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#1 kaitsdad

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Posted 04 October 2010 - 06:53 AM

Last week I had the bike over 6500 feet, and encountered some dramatic drivability problems.

The symptoms started around 6500 feet, and continued as long as I was above that elevation. Flat off of throttle, bucking, jerking, almost impossible to ride in traffic. Hard to start, and most noticeably, idle speed at 900 rpm, normally at 1100 rpm. I thought it might be the crappy Los Angeles gas, but a fill with local stuff made no difference. As soon as I dropped in altitude all symptoms cleared, and the expected drivability returned.

I've had the bike over 14,000 ft with no problems. The ECM tech bulletin has been completed, with no problem to date. The ONLY thing that has changed since my last venture to altitude in 2008 was the removal of the PAIR system. This might just be coincidental, but should be considered.

So - what do you think? ECM problem? Air pressure sensor? Dirty air filter?

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#2 ionbeam

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Posted 04 October 2010 - 07:50 AM

Last week I had the bike over 6500 feet, and encountered some dramatic drivability problems.

... Flat off of throttle, bucking, jerking, almost impossible to ride in traffic. Hard to start, and most noticeably, idle speed at 900 rpm, normally at 1100 rpm...a fill with local stuff made no difference. As soon as I dropped in altitude all symptoms cleared, and the expected drivability returned.

...The ECM tech bulletin has been completed...The ONLY thing that has changed since my last venture to altitude in 2008 was the removal of the PAIR system

So - what do you think? ECM problem? Air pressure sensor? Dirty air filter?

No troubleshooting plan for you yet, but will address some Q's.

First, the PAIR has nothing to do with your FJR's symptoms.

A dirty air filter would only show itself at higher RPMs where it may starve the engine for air, but should have no affect at lower RPMs where air demand is fairly low.

The original ECM with the altitude software error was replaced as part of a recall and *shouldn't* be a problem, even if they screwed up and swapped it with another ECU that didn't have the updated software. If you had a recall ECU failure, your driveability problems would have been reset when you shut the engine off and restarted it.

As you found out, fuel wasn't the root cause. Also, if you had a tank venting problem your driveability issues would have temporarily been relieved when you opened the gas cap to fill the tank.

Being a Gen II your FJR only has one pressure sensor. If the sensor was unplugged, shorted, or had a bug stuck in the air orifice the ECU would supply values from an emergency look-up table and you wouldn't have a clue there was a problem. For the sensor to cause a problem the reading would have to be off by a lot, but not so much as to cause the ECU to use a look-up table. While troubleshooting a problem with my FJR I have driven it with both my Gen 's intake/air pressure sensors disconnected in various combinations, and I couldn't tell any difference in the way the engine ran.

So what do that leave? I dunno, I'll keep it in the background and mull it over.

[Wild, wild, insane speculation]
Your radiator(!) is low or more likely has an air bubble which was aggravated by the altitude change causing the temperature sensor to show that the engine was not up to full operating temperature causing the ECU to use the rich start-up fuel injection map. Vacuum leaks cause high RPM at idle, rich fuel causes low idle and bogging when cranking up the throttle.
[/Wild, wild, insane speculation]

Bad decisions make for good stories.


#3 Checkswrecks

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Posted 04 October 2010 - 08:04 AM

iirc, a big part of the altitude issue was that it affected people who tended to not use the higher part of the throttle range. You might "fix" this by simply running up to a high throttle setting, while running in a lower gear.
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#4 ionbeam

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Posted 04 October 2010 - 08:19 AM

...You might "fix" this by simply running up to a high throttle setting, while running in a lower gear.

Your are right about making >30% throttle changes to force the pre-recall ECU to recalculate FI based on the pressure sensor. Also, KD had shut off the engine to refuel, this would have reset the altitude sickness problem for a while.

Bad decisions make for good stories.


#5 lnewlf

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Posted 04 October 2010 - 10:01 AM

While riding up Mt. Washington, NH I expected and got altitude probs at about 4500 ft. or so-my plan was to increase rpm's to force the ecm to recalibrate. No way I could do that in gear on that road, and pulling the clutch to rev resulted in an instant stop. I simply shut off and restarted and the bike was fine. Odd that OP bike didn't reset-I believe the problem that develops is a rich condition due to lack of O2 as altitude increases-maybe a plug fouled?

#6 ionbeam

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Posted 04 October 2010 - 10:21 AM

While riding up Mt. Washington..got altitude probs at about 4500 ft. or so-my plan was to increase rpm's to force the ecm to recalibrate. No way I could do that...resulted in an instant stop...Odd that OP bike didn't reset-I believe the problem that develops is a rich condition due to lack of O2 as altitude increases-maybe a plug fouled?

LOL, I know what you mean about Mt Washington! That is well outside of the range of 'normal'.

KD has already had the ECU recall done so there should have been no need to either vary the throttle or reset the ECU by means of key off/on again to force the ECU to re-read the intake pressure sensor.

The ECU should automatically compensate for altitude so that the engine does not run rich and the fact that it did not compensate is really the conundrum here. One reason the ECU may not have compensated and the most straight forward is the intake pressure sensor circuit had a glitch someplace. Followed by our speculation the the ECU barfed the reading due to the pre-recall software glitch. Followed by the gonzo suggestion that the ECU read the wrong coolant temperature and was running the Cold Run FI map. All three scenarios can lead to a very rich FI trim and the failure symptoms are consistent with a rich condition.

Bad decisions make for good stories.


#7 JustHoward

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Posted 18 January 2011 - 08:45 AM

I too am having this problem on my 2008 FJR.

I live in Memphis, TN, but during a rally this summer, my bike started to buck at 9,500 feet when I was in first gear at reasonably high RPMs. I stopped at my bonus location at about 10,000 feet, and when I returned to the bike five minutes later, the bike wouldn't start. So I turned it downhill, and coasted to a start, but each time I went to shift gears, the RPMs would drop off and the bike would stall.

Since I live at 450 feet above sea level, how I can simulate what's going on so we can diagnose the problem? Or have you guys figured it out yet? I have a big rally this summer and don't want to worry about my bike not making it up the mountain.

Howard

#8 Greatlakesrider

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Posted 18 January 2011 - 09:48 AM

my bike started to buck at 9,500 feet when I was in first gear at reasonably high RPMs. I stopped at my bonus location at about 10,000 feet, and when I returned to the bike five minutes later, the bike wouldn't start. So I turned it downhill, and coasted to a start, but each time I went to shift gears, the RPMs would drop off and the bike would stall.


IMO, fuel injection systems automatically compensate for altitude, some have parameter limitations for altitude, but some fuel injection systems do NOT compensate in a timely manner.

Did your bike run perfect at/below 9,500ft? How long were you above 9,500ft? Did your bike return to normal operation at/below 9,500ft?
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#9 JustHoward

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Posted 18 January 2011 - 09:51 AM

My bike worked great for 25,000 miles before high altitude, and when I descended down below 9,000 feet, it worked great again, and has continued to do so, at lower altitudes, for another 15,000 miles.

#10 Greatlakesrider

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Posted 18 January 2011 - 09:58 AM

My bike worked great for 25,000 miles before high altitude, and when I descended down below 9,000 feet, it worked great again, and has continued to do so, at lower altitudes, for another 15,000 miles.


Okay, but how long were you above 9,000ft? If it was just for a short time(less than 30min), that would fall inline with what i've experienced on certain bikes.

Edited by Greatlakesrider, 18 January 2011 - 10:06 AM.

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#11 JustHoward

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Posted 18 January 2011 - 01:35 PM

.
[/quote]

Okay, but how long were you above 9,000ft? If it was just for a short time(less than 30min), that would fall inline with what i've experienced on certain bikes.
[/quote]
I was above 9,000 feet for about 20 minutes. Five or ten minutes of that time the engine was off.