Strange idle problem. Suggestions?

[Caladin]

I've had a idle problem with my bike ('06) for some time. When you blip the throttle at idle the rpm's will drop from 1260rpm down to about a 1000rpm. The engine speed will usually pick itself back up after 5-6 seconds without being touched. The problem happens frequently but also operates normally sometimes. I have spent a fair amount of time trying to figure out the problem but cannot find anything wrong. I will list off what I have done/checked in an effort for some more suggestions as to where to look.

- TPS reads normal from 15 to 100 (no jumping around)
- Intake Air Pressure sensor reads correct and drops while cranking the motor
- Air temperature sensor reads correct.
- Air filter was just replaced.
- Throttle bodies were synchronized (using a mercury manometer and verified with a vacuum gauge).
- Spark plugs were all checked and in good shape.
- General check of boots and hoses to make sure all clamps are tight.
- Battery fully charged.

The problem seems to be worse when cold. When the engine is warm the rpm jumps back up within 1-2 seconds usually. I also have found that I sometimes cannot adjust the idle above 1260rpm. Even though the idle adjust screw is far from reaching the end of the adjustment. Attempting to increase the idle speed has no effect whatsoever on the idle speed. And dropping it back down also yields no change until it gets back to where it was previously set, at which point the rpm begins to drop as you turn the screw. Its like hitting an invisible wall the the rpm simply cannot be set over (this really stumps me).

Tomorrow I was planning on removing the TB's to look for any loose connections. As well as to try disabling the AIS to see if that has any effect. Any more suggestions as to things to check would be great. :thumbup:

 

[Motogiro]

I know you said you checked all the boots etc. but my first instinct is a vacuum leak. Almost like you already have a hole behind the throttle plates some where.

Lift the tank, take a breath, relax, look at her and say, "Baby watsamadder....Can't we work this out?"

The other thing is see if you can do a simple ECU reset. Unhook the battery for at least 5 minutes so the ECU capacitors have a chance to discharge. That computer may have gotten a bad habit from some anomaly so if you dump it you may find the cure. I'm pretty sure that you just unhook the battery for the ECU reset but scan the forum to be sure.

Also we have factory service manuals (PDF Format)that may cover ECU reset.

My gut feeling is a hole/vacuum leak.

Have fun

 

[SovietRobot]

It might have something to do with recently syncing your throttle bodies. The vaccum pressure from the throttlebodies does affect the idle.

I noticed that at certain pressures, although my tb's were synced, the idle wouldn't change no matter how many times I turned the adjustment screw, I even accidently screwed it off and the idle didn't change until I tried a different level.

 

[aussiejules]

Has this always happened or only just started, mine does it, and most cars that dont have vac decel valve (dampener) also do it. When you close the throttle butterfly sharply the computer needs to calculate what has happened and adjust, as does the air flow need to stabilie and travel through the idle circuit. I think you may be chasing a problem that isnt a problem. On a side note did the 06 need the tps recall and if s has it had it?

 

[SovietRobot]

Has this always happened or only just started, mine does it, and most cars that dont have vac decel valve (dampener) also do it. When you close the throttle butterfly sharply the computer needs to calculate what has happened and adjust, as does the air flow need to stabilie and travel through the idle circuit. I think you may be chasing a problem that isnt a problem. On a side note did the 06 need the tps recall and if s has it had it?

The 2006's didn't need the recall, at least I've never heard of one.

When my bike it cold and I rev the engine, it'll dip down for half a second, but it doesn't really do it when it's warm and I've been riding it for a while.

In fact after 1-2 hours of hard riding, throttle response is crisp and the engine is smooth. These engines were made to race.

 

[wrightme43]

Have you tried a resync on the throttle bodies?

 

[Caladin]

I know you said you checked all the boots etc. but my first instinct is a vacuum leak. Almost like you already have a hole behind the throttle plates some where.

Seems highly likely.

Lift the tank, take a breath, relax, look at her and say, "Baby watsamadder....Can't we work this out?"

I can't count the hours I have spent doing this over the months since the problem started.

The other thing is see if you can do a simple ECU reset....

Good idea. I forgot that. It haven't done that in about a year.

My gut feeling is a hole/vacuum leak.

I with you on this, the question is where?

 

[Caladin]

It might have something to do with recently syncing your throttle bodies. The vaccum pressure from the throttlebodies does affect the idle.

I have synced the throttle bodies many times since this problem has started. At no point has it ever had any effect on the idle.

I noticed that at certain pressures, although my tb's were synced, the idle wouldn't change no matter how many times I turned the adjustment screw, I even accidently screwed it off and the idle didn't change until I tried a different level.

That is interesting, and got me thinking. Today instead of syncing at idle I first set cylinder 1 to 8.5inHG. Then synced the other 3 tb's at 5000rpm to match #1. More on this in a moment.

 

[Caladin]

Has this always happened or only just started...

The problem popped up about 15k km ago. It never use to drop the idle so low and then hang there. I also use to be able to adjust the idle speed with without a problem.

... mine does it, and most cars that dont have vac decel valve (dampener) also do it. When you close the throttle butterfly sharply the computer needs to calculate what has happened and adjust, as does the air flow need to stabilie and travel through the idle circuit.

I know a certain amount of drop will be normal. But I would expect it to correct itself within 1-2 second at most.

I think you may be chasing a problem that isnt a problem.

I have thought that several times. But im certain it didn't use to be like this

On a side note did the 06 need the tps recall and if s has it had it?

No recall for '06 models. And the TPS checks out in the diagnostic. I have checked it many times, including while the systen was acting up.

 

[Caladin]

I spent the day trying to find the problem. I removed the air box, cleaned the outside of the throttle bodies and checked all hoses for cracks or lose connections. All the boots that connect to the TB's seemed to be tight. All sensor electrical connections were clean.

I have been thinking for some time that perhaps the problem was in the air passage ways where the idle set screws and and air set screws for each cylinder are. My service manual does not say anything about working on this part. So I just started taking some of it apart to look inside.

I first removed the idle set screw and spring, the cover on the left side and then followed by the 4 air set screws for each cylinder. All of these parts have a small o-rings to seal them. The idle set screw o-ring seemed to be dirty so i cleaned it up and then checked that it had a good seal still. I used compressed air to blow out the shaft and spring that that idle set screw pushes on. It is the part on the right of the picture below. You can see the parts were black and dirty. (One air set screw was cleaned before the picture)

I cleaned all the the parts with some brake cleaner. Be careful that the o-rings, washer and spring do not pop off the air set screws while remove these parts. They are just a loose fit and could come off if bumped. I flushed cleaner through the air ways as well. Followed by more compressed air to help remove any left over cleaner or possible debris.

After reassembling everything I fired the bike back up and let it warm up. Once it warmed up I set the isle speed with the idle set screw. I then set cylinder 1 to 8.5inHG with a vacuum gauge. I then connected my manometer and used that to syn the TB's at about 5000rpm. After doing this found that I was now able to set my idle up higher then before. I have it set to 1320 to 1360 when really warm. I couldn't do this before no matter how much i adjusted the set screw.

With several tests now I have been unable to get the bike to stumble like it use to when bliping the throttle. I have tried it hot and cold and so far today it hasn't dropped below 1200rpm when coming off the gas. And the idle always jumps back to speed within 1-2 seconds at most.

Time will tell if the problem is now solved. But it sure seems like it is to me. :rockon: I will let it sit over night and test it again tomorrow. I really can't be sure if it's the cleaning that solved the problem of the difference in TB syncing method.

 

[maverick1970]

Frakin outstanding. Gotta love it when you can fix a problem. Keep us updated...

 

[opds9091]

can anyone tell me how to bring my idle up a little, if you have a picture of the bolt, screw..etc, it would help me out big time. My bike idles at 900-1000, and when down shifting sometimes the bike shuts off and i have to hit the starter button again.

 

[Boneman]

can anyone tell me how to bring my idle up a little, if you have a picture of the bolt, screw..etc, it would help me out big time. My bike idles at 900-1000, and when down shifting sometimes the bike shuts off and i have to hit the starter button again.

Idle adjuster is under the left side of your gas tank. Just crouch down and look up under the side of your tank and you will see it. I believe it has a Philips head screw in it and you just turn it to increase or decrease your idle speed. Your idle should be around 1,300.

 

[opds9091]

Thanks BONEMAN, you wouldn't happen to have a picture of it, I am no mechanic but I am starting to learn, if not no problem THANK YOU VERY MUCH!!!!!!!