Rough at flat / constant throttle

Started by KPhinney, April 10, 2018, 10:59:49 AM

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booger

I went through this with Chris and he told me almost nobody replaces these. Also asked if I knew someone who could do the work to please pass the name on. You have to remove the butterflies and slide the shaft out. Another expert who rebuilds TBs told me he would not touch it. Suffice it to say, replacing the TPS is not an option. Going further, it's been discussed that the TPS itself is not the issue, but the seal around the butterfly shaft leaking vacuum.

Appears you need to replace the throttle bodies if you have a problem with the sensor.

The fueling with these bikes has always been tricky, which is why everybody who goes out and gets a dyno tune always reports a night and day transformation.
Everybody got a plan 'till they get punched in the mouth - Mike Tyson

2001 M900Sie - sold
2006 S2R1000 - sold
2008 HM1100S - sold
2004 998 FE - $old
2007 S4RT
2007 Vespa LX50 aka "Slowey"
2008 BMW R1200 GSA

Moronic

I'm reluctant to go into much more detail here - after all, the TPS may not be the issue and probably isn't.

Nevertheless, a couple of points from experience and a bit of research.

1. The TPS on these throttle bodies can be replaced from the outside. Best demonstration is this 2014 post on British forum www.ducatiforum.co.uk:

https://www.ducatiforum.co.uk/threads/how-to-749-999-tps-replacement.24535/

This is for a 749, but the sensor and the way it connects with the throttle body is the same. A lot of the post deals with getting to the TBs. The pics of TPS removal are near the bottom.

Here is the TPS socket, with the part removed:



Interestingly, the poster said his first replacement TPS was faulty. He went through the process again with another replacement TPS, and reports at the bottom of the post a full cure.

The sensor is also used on some Italian cars. It appears from the thread following this post that there is even a fiat factory puller designed to remove this TPS.

2. There are suggestions floating around on the net that what causes these to go bad can be fuel or vapour leaking into the socket area shown above. Protruding into that socket is the butterfly shaft. I have no comment to make on this.

3. I have had put to me the proposition that fuelling issues arise on these bikes as they age because air leaks into the TBs through worn seals on the butterfly shafts.

Against that theory:

a) A revered long-time Ducati tech told me the theory made no sense as a diagnosis.

b) In response to the theory, my 35k mile TBs - which were quite worn at the TB seals/bearings - were replaced with a much fresher used set. (Unfortunately) the TPS was swapped at the same time - i.e. the old TPS was fitted to the fresher TBs. The problem remained.

c) It was these fresher TBs that were replaced more recently with yet another fresh-ish used set, which came with its own TPS. Night and day difference.

I offer these observations as observations. I am not a Ducati tech. Would be interested to hear any industry gossip the techs on this board could contribute.

KPhinney

Quote from: howie on April 13, 2018, 04:40:50 PM
You cannot set that TPS manually, it is not adjustable.  If you can't cat your software running a shop shouldn't charge a lot to set it.

Good to know.  The threads sometimes get dicy about the year and engine. 

Unfortunately, the PC I keep in the garage for the Triumph wouldn't boot.  It's been sitting for about 5 months.  I'll find another and give the TPS reset a go this week.

booger

Quote from: Moronic on April 14, 2018, 08:53:26 PM
I'm reluctant to go into much more detail here - after all, the TPS may not be the issue and probably isn't.

Nevertheless, a couple of points from experience and a bit of research.

1. The TPS on these throttle bodies can be replaced from the outside. Best demonstration is this 2014 post on British forum www.ducatiforum.co.uk:

https://www.ducatiforum.co.uk/threads/how-to-749-999-tps-replacement.24535/

This is for a 749, but the sensor and the way it connects with the throttle body is the same. A lot of the post deals with getting to the TBs. The pics of TPS removal are near the bottom.

Here is the TPS socket, with the part removed:



Interestingly, the poster said his first replacement TPS was faulty. He went through the process again with another replacement TPS, and reports at the bottom of the post a full cure.

The sensor is also used on some Italian cars. It appears from the thread following this post that there is even a fiat factory puller designed to remove this TPS.

2. There are suggestions floating around on the net that what causes these to go bad can be fuel or vapour leaking into the socket area shown above. Protruding into that socket is the butterfly shaft. I have no comment to make on this.

3. I have had put to me the proposition that fuelling issues arise on these bikes as they age because air leaks into the TBs through worn seals on the butterfly shafts.

Against that theory:

a) A revered long-time Ducati tech told me the theory made no sense as a diagnosis.

b) In response to the theory, my 35k mile TBs - which were quite worn at the TB seals/bearings - were replaced with a much fresher used set. (Unfortunately) the TPS was swapped at the same time - i.e. the old TPS was fitted to the fresher TBs. The problem remained.

c) It was these fresher TBs that were replaced more recently with yet another fresh-ish used set, which came with its own TPS. Night and day difference.

I offer these observations as observations. I am not a Ducati tech. Would be interested to hear any industry gossip the techs on this board could contribute.


OK then good stuff! It's the throttle butterfly shaft that I was thinking was the biggest bugaboo. If we are not to accuse the shaft seals of leaking, then this revelation concerning how to go about replacing the TPS is useful and something I would try myself. However if it is true that the seals can leak and do, that's another thing entirely. The butterfly plate screws are peened to the shaft and there's the challenge of reinstalling the plate perfectly concentric to the bore. The thought of that whole thing makes me nervous.
Everybody got a plan 'till they get punched in the mouth - Mike Tyson

2001 M900Sie - sold
2006 S2R1000 - sold
2008 HM1100S - sold
2004 998 FE - $old
2007 S4RT
2007 Vespa LX50 aka "Slowey"
2008 BMW R1200 GSA

Moronic

Hi Booger,

the shaft seals - from memory they are just long nylon bearings - can and do leak eventually, as they wear. That's established.

The question is whether in practice it is leakage through there or a TPS fault at the root of poor running that can be sourced to the TBs.

My experience - and as I say, some advice - suggests strongly that the key is the TPS and not any air leak that might develop at the butterfly shafts.

For example, the throttle bodies that came off my bike most recently are in excellent shape at the butterfly bearings. I could add more anecdotal stuff but won't here.

Certainly air leakage there will not be a problem for KPhinney given the low mileage on his bike.

You are quite right that replacing those bearings/seals would be a specialised job, even assuming the relevant parts could be purchased. I imagine there must be someone out there who could rebuild those TBs - if they were paid enough.

Howie

If those seals are very worn they could cause the problem.  A little worn?  Closed loop will compensate and open loop the vacuum leak is too minimal to be of consequence.   Anyway, easy enough to check.  A little oil (to seal the leak)  or something burnable, like carb cleaner, or, if you are brave enough, propane it the area of the throttle seals and see if the idle tries to change.  Anyway, since you bought the bike used all basic settings should be verified before going further.

KPhinney

I appreciate all of the help so far.  I think I've located the cause.  First, let me say I got JPDiag running without much hassle.  The plan was to reset the TPS first.  Turned out it was at 2.2deg.  I'm not sure if this is perfect or just close, but the software wouldn't allow me to reset it so I' assuming it's within spec, and the bike ran just as rough as it had been.

Something Howie said got me thinking.....

Quote from: howie on April 10, 2018, 11:42:16 AM
I'm not sure about this, but, if closed loop can't compensate, your open lid may be the problem if you are running the computer at factory settings.  Partially close off the air box and see if it gets better.

I tried this and it didn't seem to make much of a change.  Not for good or bad. 

Tie this in with what S21FOLGORE asked:
Quote from: S21FOLGORE on April 10, 2018, 01:18:25 PM
Do you mean by that the stock air box lid is cut off ? Or are those three items (Termi pipes, ECU, open top air box rid) the ones sold as Ducati Performance kit?

I looked up the Termi Ducati Performance kit when he asked this, to make sure that's what I had.  In addition to the pipes and ECU, the Performance Package also lists a high flow air filter. 



Then it dawned on me.  When I took delivery of the bike, it was covered in desert dust and dirt.  It came from Arizona and to this day I'm still finding red dirt in the cracks.  So naturally, the first thing I did was to buy a K&N air filter and swap it in. 

I went to the spare parts drawer and pulled out the filter that came on the bike.  In with the old air filter and it is definitely running smoother than it had prior. 

My questions are:

Are there good posts that show what an in-spec S4R looks like on JPDiag?  (Feel free to point me to other posts if that's been covered, but I wanted to wrap this post up with a possible solution.)
Could the filter swap have fixed the rough running or did I tweak something else unknowingly?  I will do the swap again this weekend to see if I can feel the difference. 
Can I use JPDiag to measure the air flow difference between these filters?  I'd like to set a base line for a good air flow and filter. 
Has anyone experienced this?  What filters should be used with the Ducati Performance Kit?
What