Idle problem solved

New thread to make the topic a little easier to find in the future. As some of you know I've been trying to understand and fix the idle problem in this Thread.

Short story, discovered cylinder 2 steals fuel from cylinder 1 at idle via the IAC pipe that links both throttle bodies. This can cause rough running, fouled plugs and much frustration! As I have an aftermarket ECU fitted and the diagnostic tools to monitor the AFR in both cylinders simultaneously I was able to rule out any problem with the programming of the ECU. I wasn't planning on going much further as I could mitigate the problem somewhat with changes to the ECU. But it still bugged me, so yesterday I pulled the throttle bodies off. Bit of a mess oil everywhere, I put this down to a remnant of the bad old days before Norton got a workable solution to the oil in the airbox problem.




I then took the throttle bodies to an engineering shop and had them machine a suitable plug.



Reinstalled the throttle bodies and without the IAC assembly to contol the idle I opened the throttle butterflies a touch using the throttle position screw. The result was pretty spectacular, no backfiring, hesistancy etc. It idled PERFECTLY - you could hear it with your ears and you could can see it on the oxygen sensor display. Video here.



Next step is to see if I can add the IAC valve back so I don't need to worry about holding the throttle open when cold. I have an idea as to how to achieve this. I couldn't believe the difference - best way to describe the sound of the engine would be happy!

If you have a stock bike and want to try this then you may need to keep the IAC valve electrically connected in case it throws an error. You must block the balance pipe between the throttle bodies NOT the IAC pipe that leads to it.

Thanks for keeping up the good work, following with interest down here in the Tron.

ntst8 said:

Thanks for keeping up the good work, following with interest down here in the Tron.

Click to expand...

Come on up and I'll stick a probe up your back end! But seriously I'm in Pukekohe, feel free to bring your bike up. What exhaust system are you running? Needs to be CAT free and not have a crossover pipe to measure the lambda values.

iwilson said:

New thread to make the topic a little easier to find in the future. As some of you know I've been trying to understand and fix the idle problem in this Thread.

Short story, discovered cylinder 2 steals fuel from cylinder 1 at idle via the IAC pipe that links both throttle bodies. This can cause rough running, fouled plugs and much frustration! As I have an aftermarket ECU fitted and the diagnostic tools to monitor the AFR in both cylinders simultaneously I was able to rule out any problem with the programming of the ECU. I wasn't planning on going much further as I could mitigate the problem somewhat with changes to the ECU. But it still bugged me, so yesterday I pulled the throttle bodies off. Bit of a mess oil everywhere, I put this down to a remnant of the bad old days before Norton got a workable solution to the oil in the airbox problem.

I then took the throttle bodies to an engineering shop and had them machine a suitable plug.

Reinstalled the throttle bodies and without the IAC assembly to contol the idle I opened the throttle butterflies a touch using the throttle position screw. The result was pretty spectacular, no backfiring, hesistancy etc. It idled PERFECTLY - you could hear it with your ears and you could can see it on the oxygen sensor display. Video here.



Next step is to see if I can add the IAC valve back so I don't need to worry about holding the throttle open when cold. I have an idea as to how to achieve this. I couldn't believe the difference - best way to describe the sound of the engine would be happy!

If you have a stock bike and want to try this then you may need to keep the IAC valve electrically connected in case it throws an error. You must block the balance pipe between the throttle bodies NOT the IAC pipe that leads to it.

Click to expand...

Great work. We’ll try that. Thanks for sharing.

iwilson said:

New thread to make the topic a little easier to find in the future. As some of you know I've been trying to understand and fix the idle problem in this Thread.

Short story, discovered cylinder 2 steals fuel from cylinder 1 at idle via the IAC pipe that links both throttle bodies. This can cause rough running, fouled plugs and much frustration! As I have an aftermarket ECU fitted and the diagnostic tools to monitor the AFR in both cylinders simultaneously I was able to rule out any problem with the programming of the ECU. I wasn't planning on going much further as I could mitigate the problem somewhat with changes to the ECU. But it still bugged me, so yesterday I pulled the throttle bodies off. Bit of a mess oil everywhere, I put this down to a remnant of the bad old days before Norton got a workable solution to the oil in the airbox problem.

I then took the throttle bodies to an engineering shop and had them machine a suitable plug.

Reinstalled the throttle bodies and without the IAC assembly to contol the idle I opened the throttle butterflies a touch using the throttle position screw. The result was pretty spectacular, no backfiring, hesistancy etc. It idled PERFECTLY - you could hear it with your ears and you could can see it on the oxygen sensor display. Video here.



Next step is to see if I can add the IAC valve back so I don't need to worry about holding the throttle open when cold. I have an idea as to how to achieve this. I couldn't believe the difference - best way to describe the sound of the engine would be happy!

If you have a stock bike and want to try this then you may need to keep the IAC valve electrically connected in case it throws an error. You must block the balance pipe between the throttle bodies NOT the IAC pipe that leads to it.

Click to expand...

I’m more concerned about the oil in the throttle bodies. That alone causes issues.

Hello iwilson , Is the red plug made of rubber or plastic ? And did you insert this into the spigot where the throttle body IAC hose attaches ? Can you give us the OD's of the Red plug and length ? This way maybe we can find or make something ?

Voodooo said:

I’m more concerned about the oil in the throttle bodies. That alone causes issues.

Click to expand...

Yes he is drawing a lot of oil into the throttle bodies.

iwilson said:

Come on up and I'll stick a probe up your back end! But seriously I'm in Pukekohe, feel free to bring your bike up. What exhaust system are you running? Needs to be CAT free and not have a crossover pipe to measure the lambda values.

Click to expand...

Very kind thankyou, well part 2 of the offer any way .
I'm grounded this weekend but will pm you and see if we can make it work.
Nearly forgot, factory shorties and decat pipes so should be all good.

great work

have you got a pic to install plug ?
You must block the balance pipe between the throttle bodies NOT the IAC pipe that leads to it.

cheers
Paul

So , If i understand that : When you block the passage between you will also block the IAC hose leading to it. 2 birds , one stone. Set the idle with fully warmed up engine and use something like this to keep your bike running when cold . This is my cruise control. Also don't forget the lock nut for the throttle body butterfly valves to keep the adjustment secure.

Voodooo said:

I’m more concerned about the oil in the throttle bodies. That alone causes issues.

Click to expand...

This is why I've changed my setup so the crankcase breather no longer enters the airbox. I'll guarantee your throttle bodies will end up the same - if there is oil in your catch bottle then there's oil going into your throttle bodies! My bike was retro actively fitted with the Norton oil in the airbox fix, so it probably suffered quite badly up to that point.

Here's some photos of the stock setup and the plug. Just to be clear we are blocking the pipe that connects the throttle bodies not just the hole that air enters from the IAC. The plug has to reach deep inside to block the tube running between the throttle bodies.



With the plug inserted



Stock with the metal sleeve the IAC pipe fits onto.



Stock setup with the complete IAC assembly



IAC assembly ready to insert into the throttle body.



Plug width, it widens out further down to match the metal sleeve. This is the diameter to fit inside the balance pipe.



Length of the plug to insert fully into the balance pipe.



As fitted to the engine.


This is just a temporary plug I had made to see if it solved the problem. The engineer used something called PU30 (I think) it can take a couple of hundred degree's of temperature. I certainly wouldn't use it as a permanent fix - I don't know how resistant it is to fuel degradation.

The downside is idle control. The engine should sound a lot happier at idle with the plug inserted, but without the IAC controlling the idle speed you'll have to adjust the throttle position screw until you arrive at an acceptable warm idle speed, this will probably mean needing to manually keep the throttle open a touch when cold. Personally I'd prefer the ECU to take care of this so I'm working on an idea to retain the IAC but without the charge stealing issues.

Lastly your results may vary! I noticed straight away that once the balance pipe was blocked the engine was running much richer - something I could easily manage with my programmable ECU. If you don't have o2 sensors then perhaps your engine will continue to run very rich. If you do have o2 sensors the ECU should be able to trim enough fuel to get the engine close to lamdba 1 (14.7:1). My engine was something like .78 lambda or 11.4:1 at idle. But again your results may vary. Pretty much every garage these days has a gas analyser. Catalytic converters will also fail when exposed to a consistently rich AFR.

Thanks for the measurments . Best of luck with the rest too. Did we ever get an answer about the fuel injector screens not being used by Norton ?

TonyA said:

Thanks for the measurments . Best of luck with the rest too. Did we ever get an answer about the fuel injector screens not being used by Norton ?

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Not that I’m aware of. I’ve refitted my injectors with the filter and haven’t seen any problems.

iwilson said:

The downside is idle control. The engine should sound a lot happier at idle with the plug inserted, but without the IAC controlling the idle speed you'll have to adjust the throttle position screw until you arrive at an acceptable warm idle speed....

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SC provided Norton with a routine for setting the throttle position screw via the ECU software. Would this routine still be valid without the IAC?

No . Idle will be manually set with a screw like carbs .

comet said:

SC provided Norton with a routine for setting the throttle position screw via the ECU software. Would this routine still be valid without the IAC?

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That procedure is to set the range of the throttle position sensor. If you adjust the throttle position screw then you are opening the throttle butterflies slightly and moving the throttle position sensor. But the ECU doesn't know this is the new zero position and thinks the throttle is being held open i.e. not at zero. The procedure is to then tell the ECU that this is the new zero position. The ECU has an auto-zero function that can be switched on to allow the ECU to work out where zero is - (this is why you shouldn't manually touch the throttle when starting it can get the ECU confused). I don't know if the factory SC ECU's have this enabled or not.

Just following on from the above. Here is the analogue inputs screen for the ECU, showing the throttle position sensor settings (TPS). Bottom left is the explanation of what the setting does. I have a factory stock map loaded and although you can see the two options in the drop down box, neither actually appears when you open the page so I don't know which one is used (this software is designed for my more advanced ECU, the factory maps were developed for a different ECU so opening the factory maps in this software means some settings need to be manually entered).

What I would like to add is if you're thinking of buying either this or another aftermarket ECU be prepared for a very steep learning curve if you're not proficient with the in's and out's of EFI engines. There are literally hundreds of different settings, many of which may as well be in Latin for all the sense they make!

iwilson said:

What I would like to add is if you're thinking of buying either this or another aftermarket ECU be prepared for a very steep learning curve if you're not proficient with the in's and out's of EFI engines. There are literally hundreds of different settings, many of which may as well be in Latin for all the sense they make!

Click to expand...

or Greek for that matter.

Figured I'd put everything back on today and go for a ride. The instant I said it, the rain began to fall (it really did)! Continued on in any case and took the opportunity to do a little bit more testing and tweaking. So today's blockbuster see's me starting from cold (it's still pretty warm in NZ), allowing the bike to warm up till hot (100C), at which point the plot thickens as I attempt a couple of hot restarts. If that isn't edge of your seat stuff, I then attempt to rev the engine to see if it'll stall when attempting to recover to idle speed. Is it a tragedy, a comedy or just 3 minutes you'll never get back...



Other than revving the engine, at no point did I touch the throttle. Really wondering if I should just leave it there. I have the throttle position screw set so hot idle is a touch higher than factory, cold idle is quite a bit lower but with both cylinders working as they should it seems happy enough.

Could you reduce the hot idle down to around 1000rpm and install a simple throttle lock device for the cold idle. My bike doesn't take long for it to warm up from cold and settle to around 1200rpm, maybe 2 mins at most, which is about the time it takes to do up my chin strap and get my gloves on