Another TPS question

[daviddowns2000]

I had the TPS recall done on my '05 several years ago. Things were fine until a few days ago, when erratic idling began. If the TPS diagnostic goes smoothly from 17 to 101, can I pretty much rule out a bad TPS?

I suddenly had to adjust the baseline idle up from about 800 to 1100 or so because of the off-throttle bucking and have no idea why the idle speed just one day went down a few hundred RPMs. Now, the idle is somewhat better but still unstable, sometimes flickers from 1100 to as low as about 500 (indicated on bike's tach), then flicks back up to 1100. At least it isn't stalling out any more.

Any suggestions (other than reading all the existing threads on this topic, which I have partially done) before I delve into it and start breaking things?

You Tube video (with audio of idle): https://www.youtube.com/watch?v=jHHs9hq7s2s&feature=youtu.be

 

[Fred W]

I had the TPS recall done on my '05 several years ago. Things were fine until a few days ago, when erratic idling began. If the TPS diagnostic goes smoothly from 17 to 101, can I pretty much rule out a bad TPS?

No. You can say that the TPS is sending a good signal right at that moment, but you can't say that it always does.

The classic TPS failure symptoms only come on after the TPS gets heated up. When cold it may look fine and then start acting up only after an extended highway run. Also, just because an updated TPS was installed doesn't mean that part will never fail again. TPS sensors fail on many other bikes besides 1st Gen FJRs.

I suddenly had to adjust the baseline idle up from about 800 to 1100 or so because of the off-throttle bucking and have no idea why the idle speed just one day went down a few hundred RPMs. Now, the idle is somewhat better but still unstable, sometimes flickers from 1100 to as low as about 500 (indicated on bike's tach), then flicks back up to 1100. At least it isn't stalling out any more.
Any suggestions (other than reading all the existing threads on this topic, which I have partially done) before I delve into it and start breaking things?

You Tube video (with audio of idle): https://www.youtube.com/watch?v=jHHs9hq7s2s&feature=youtu.be

Your idle in that video, sounds pretty typical to me. When you set the idle at 1100 rpm (or higher) it does tend to surge like that. It shouldn't stall, but it does surge.

I find that, with a good Throttle Body Sync, lowering the idle to 1000 rpm the idle seems to steadies out and not surge so much. I'm not sure exactly why that is, but my '05 has always been that way. I keep the idle up at 1100 as it seems to decrease the off to on throttle transition a little bit.

 

[daviddowns2000]

Thanks Fred, good points. I did run the TPS diag both cold and warmed up, same result, and the idle is erratic when cold as well as after a long ride. The video was done after resetting the idle to 1100+/-. I guess the plan now is to check the plug caps and wires, sync the TBs and see if any of that helps. This cropped up after I replaced the rear wheel ABS sensor but I know that has to be only coincidence.

 

[Denver_FJR]

...

I suddenly had to adjust the baseline idle up from about 800 to 1100 or so because of the off-throttle bucking and have no idea why the idle speed just one day went down a few hundred RPMs.

...

Bad gas? Siphoning the tank and filling with fresh fuel is an easy first step.

Are symptoms only related to idle? No other throttle/drive-ability issues?

 

[Fred W]

800 is way too low. Yes that will result in bucking and stalling.

Try setting the idle down to 1000 rpm (from 1100) and see if it smooths out. Like I said, mine idles like yours does in the video when it's at 1100. I just don't worry about it.

 

[3dogs]

Try tapping on the tps with a screwdriver handle while idling. If the idle changes from wacking the tps--you've got a tps problem. Try this both cold and hot.

 

[RaYzerman19]

I`d also recommend a cleaning of the TBS screws, and when doing the TBS, set the screws at 1 turn out to start.

 

[daviddowns2000]

...

I suddenly had to adjust the baseline idle up from about 800 to 1100 or so because of the off-throttle bucking and have no idea why the idle speed just one day went down a few hundred RPMs.

...

Bad gas? Siphoning the tank and filling with fresh fuel is an easy first step.

Are symptoms only related to idle? No other throttle/drive-ability issues?

I wasn't sure if there were any other issues so I did some testing this morning. There is a definite stutter when going abruptly WOT at any of the speeds I tried, that is not present when accelerating gradually. Once or twice it seemed not to stutter, but most times (maybe 15 or so) it did. After the initial puh puh puh puh, it accelerates normally as far as I can tell. IIRC, steady WOT seems normal but I'd have to do it again to be sure.

 

[daviddowns2000]

I bought some new spark plugs, figured I'd pop 'em in and sync the TBs. Removed the old Iridiums, put in new CR8E's, fired it up and it sounded normal again...go figure! Didn't get to sync the TBs because the mercury had disappeared from my Motion Pro tool, but I rode today and it was just fine, no erratic idle, no stutter when opening the throttle. The old plugs looked perfect but they were probably 15K miles old, so maybe that was it. Whatever, it's running fine again and I'm happy.

 

[Fred W]

Hmmm. Maybe I wasn't hearing the problem?

Here's a crummy video (taken on my compact digital camera) of my bike taken today with the idle set to 1100 rpm. Ignore the steam, I had just washed the winter road crud off and the radiator was still wet.



Note that my idle has always sounded like this at 1100 rpm. Note the lean stumble misfires especially in the exhaust note

Now here's a repeat video with the idle dropped to 1000 rpm.

 

[daviddowns2000]

It's a puzzle to me. I don't know why the idle dropped in the first place and I don't know enough about ignition to understand why new plugs fixed it. Seemed like a fueling issue to me, but I'm not an expert. I tapped on the TPS, checked ecu connections, looked at fuel hoses for kinks, etc. I guess I could put the old plugs back in to see if they were really the culprit, but the bike is running great now so I'm not going to worry about it. Anyway, thanks to all for the suggestions.