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 high idle after tbs

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Eire1400
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PostSubject: high idle after tbs   high idle after tbs Icon_minitime1Sun Feb 07, 2021 2:55 am

Afternoon all,
2010 GRiSO se with beetle map & GPR pipe with both baffles.
Bought a carb tune and sync'd throttle bodies with the help of the great write up on this site.
Everything went as planned but my idle is now high. Starts at 2k then settles to 1.6k.
I have done the TPS reset twice (opened throttle between) , reset auto learning but still high.
wasn't noticing any change on rev counter when i was adjusting CO2 trim so left it at 0.

Had the sync perfect at 4k rpm then at idle one side was slighter higher so opened air screw (both air screws were open when I checked at the start.

Checked vales before I did throttle sync. exhausts were a little tight.

Could some one point out what i may have done wrong or what i can look at to get my idle down. should be around the 1200? think mines was always a little more than that.


thanks in advance.
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GuzziSteve
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Sun Feb 07, 2021 4:09 am

You haven't done anything wrong. Sometimes on these FI w/auto reset, the sync to be correct with your idle has to be out of sync a bit. Different on each bike where the grey area is w/sync screw moving plate and TPS no mater if you reset it or not. Physically moving plate for sync gets you more fuel and raises the idle.
There is another thread on this subject.

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paulbrice
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Sun Feb 07, 2021 6:46 am

+1 What Steve said....I balance the TBs for variety of riding normal speeds/revs by riding around with vacuum dials fitted, but for idle I balance it for 'most stable idle only' with vacuums offset (it doesn't seem to mind). I always make sure one of the bleeds is completely shut as that helps & it sort of 'feels like' you have to adjust the air bleed to the point the stepper motor can actually control idle else too much air in the basecase. I have Marks map so no auto learning and no lambda effects.
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Pete Roper
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Sun Feb 07, 2021 1:30 pm

How many Km has the bike done? Where do you run the oil on the dipstick? When were the TB's last removed and cleaned thoroughly?

High idle is usually caused by one of two things. A grubby, gummed up stepper motor or filthy throttlebodies.

Generally speaking, if correctly tuned, the stepper does very little and only moves within a very small amount of its range. That means if it does become loaded with oil contaminants pumped out by the sump being over-filled and then the tune is changed significantly, (By changing from having both air bleeds open to only one for instance.) it may suddenly be asked to move out of this very narrow 'Comfort Zone' and if it is significantly soiled it simply may not be able to compensate and the idle will remain significantly different from the required target.

If the throttle bodies themselves are filthy you can end up with the situation where when the TPS is recalibrated with the engine off and the throttle plates 'At rest' it will recalibrate to 4.8 just fine but when the engine is started the air pressure on the back of the plates will pull them around on the caked on crud in the bore of the TB causing the TPS value to increase. It won't do it by much but it doesn't have to. Once the ECU sees a value around or over 5.0 it will start advancing the spark. More advance and the idle will rise.
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Eire1400
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Mon Feb 08, 2021 6:14 pm

Hi Pete and thanks for reply.
Bike has around the 23000 klms mark. Oil usually ran at close to max.
Great explanation of the two causes, is there a thread on cleaning stepper motor?
From talking to a buddy, he reckons there would be no harm in running thru the Throttle body sync again but this time after a ride when the bike is properly warmed up.
I was above the 60 degrees last time but it was just from idle.
Suppose it would do no harm while I study up on stepper motor cleaning. Will look at that next.
Thanks again for the help all.




Pete Roper wrote:
How many Km has the bike done? Where do you run the oil on the dipstick? When were the TB's last removed and cleaned thoroughly?

High idle is usually caused by one of two things. A grubby, gummed up stepper motor or filthy throttlebodies.

Generally speaking, if correctly tuned, the stepper does very little and only moves within a very small amount of its range. That means if it does become loaded with oil contaminants pumped out by the sump being over-filled and then the tune is changed significantly, (By changing from having both air bleeds open to only one for instance.) it may suddenly be asked to move out of this very narrow 'Comfort Zone' and if it is significantly soiled it simply may not be able to compensate and the idle will remain significantly different from the required target.

If the throttle bodies themselves are filthy you can end up with the situation where when the TPS is recalibrated with the engine off and the throttle plates 'At rest' it will recalibrate to 4.8 just fine but when the engine is started the air pressure on the back of the plates will pull them around on the caked on crud in the bore of the TB causing the TPS value to increase. It won't do it by much but it doesn't have to. Once the ECU sees a value around or over 5.0 it will start advancing the spark. More advance and the idle will rise.
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Pete Roper
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Mon Feb 08, 2021 6:52 pm

Don't run the oil anywhere near the 'Full' mark on the stick. Start off with it half way between 'Add' and 'Full' and don't add any unless it drops off the stick.

As for cleaning the stepper? Pull the hose off the airbox and run the stepper test with Guzzidiag while spraying some TB cleaner down the hose and blipping the throttle. It'll cough and splutter and blow some smoke but it usually helps if the stepper is gummed up.

Whip the air filter out and check for oil in the airbox and have a squizz up the inlet tracts with a mirror to see how filthy the TB's are. Chances are they will be very grubby. If that is the case it's time to take them off and give them a thorough clean.

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Eire1400
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Mon Feb 08, 2021 7:58 pm

Lovely. Job for the weekend! will report back. Thanks
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Eire1400
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PostSubject: Re: high idle after tbs   high idle after tbs Icon_minitime1Mon Feb 22, 2021 9:05 pm

Just to update here,
I redid my tb sync after a spin for 10miles to warm bike up properly.
Now at 4 k its level and its not far off level at idle too so I left both bleed screws closed.
cycled the stepper motor thru GuzziDiags. Was unsure if I got the correct tube out of airbox ( clear tube on front left of airbox? looks to just a drain tube?) But squirted carb cleaner down it anyway. No cough or splutter but idling around the 1250 rpm and stayed there all weekend.

Thanks for the help again.
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