Jump to content

High Cold Idle


Thirls

Recommended Posts

Please Help ! Hello all, whilst I've researched and read a lot from VFRD this is my first request for help as I cant seem to resolve my problem, which apparently is well documented and experienced amongst all us VFR riders with many threads on here about this topic !!  Some of you will now yawn I guess ? - the old high cold idle problem !! So my bike is a recently purchased 2000 MY 5th gen FIY model 17K miles but had been in dry storage and not started for 7 years. So with the fuel tank drained and fresh fuel, coolant system drained flushed and refilled, engine oil drained and renewed and a new battery she burbled into life pretty much straight away, but after a few seconds went straight upto 4000 RPM and stayed there ! I've had the air box off and throttle bodied off, renewed the thermostat and ensured the dreaded cold start wax unit levers are all free and moving correctly, and the coolant inlet and outlet ports are free and checked that the unit works which it does, i.e. the lever extends (when heated with a hair drier) but se still sits at 4000 RPM !! So what else could hold the revs high ??,  I am assuming an air leak bypassing the throttle discs but I have checked all the vac hoses and nothing obvious. I really don't know what else to look at now, are the fuel injectors worth checking ? - if they are faulty / gummed up could that cause a high idle ?? The FI light is not on so am assuming no faults,  …. any more advice would be much appreciated.

Link to comment
Share on other sites

  • Member Contributer

Good chance Injectors and Throttle bodies need cleaning. Could also be the throttle body boots leaking, loose clamps or broken boots.

Link to comment
Share on other sites

Ive had throttle boddies off so I know all the vac hoses and rubber boots are good and sound, just that I didn't disassemble injectors ….. but I don't know if they are dirt etc whether that could jack up the idle speed ??

 

Link to comment
Share on other sites

I've had this happen a couple of times on my FiY, after changing the coolant. The hot coolant needs to get to the wax unit for it to work, if there is an air lock, it won't.

I've cleared mine by a combination of:

Squeezing the rad hoses to 'burp' the system

Letting the system cool, checking and topping up the coolant at the rad cap and re-starting 

Leaning the bike as far left as possible when it's running

Reving to 6-7k repeatedly

 

Eventually the coolant has reached the wax unit and the revs have dropped back to normal tick over.

 

Hope this works for you.

 

Link to comment
Share on other sites

Thanks I’ll give it a try but I’m not confident because although I know the factory set the adjustment nuts on the wax unit push rod, I have actually backed them right off so I can be sure it is not holding the starter valves open... 

 

There must be something else which is holding the revs high, but I just don’t know what else could do this ?? 

Link to comment
Share on other sites

  • Member Contributer

If not the wax unit, it will most likely be an air leak.

Check the throttle butterflies are closing all the way. They are NOT used for the idle cycle, which is what causes the sudden lurch from idle to initial throttle!

If you can get something to block all four air intakes, then block one at a time first whilst bike idles & see if the idle drops on any particular one.

You could try some grease to seal the butterflies or squirt some quick start into each intake in turn & check the result. You can also squirt it at the intake boots & vacuum tubes under the throttle bodies & see if the engine picks up.

 

Check that the flapper valve vacuum tube is connected &/or blocked off correctly, same the the MAP sensor hose at rear right of lower airbox half.

I assume you have adjusted the idle screw ? It's on the right side of the throttle body next to the starter valves, accessed via a small hole in the right frame rail covered with a rubber bung if it there.

Also the starter valves can leak, squirt some quick start or WD40 around them, as the O-rings n=may have perished without use, they are 20 years old.

 

If you want to check the injectors, just disconnect one at a time & the result should be the same for all four.

 

Let us know how you get on.

 

Link to comment
Share on other sites

  • Member Contributer
54 minutes ago, Thirls said:

Thanks I’ll give it a try but I’m not confident because although I know the factory set the adjustment nuts on the wax unit push rod, I have actually backed them right off so I can be sure it is not holding the starter valves open... 

 

There must be something else which is holding the revs high, but I just don’t know what else could do this ?? 

I do know of a 2003 that had fast idle when cold of 4000rpm. After having the injectors cleaned and flow checked as well as a clean of the Throttle bodies the bike was back to normal. Considering your bike has sat for 7 years in storage your injectors can't be too healthy. You also have a few good suggestions from Mohawk.

Link to comment
Share on other sites

Thanks all for replies so far 👍. So tomorrow’s task is looking for an air leak ! I feel I now have an intimate relationship with the lower half air box (and the plethora of things you have to disconnect to remove it !) Guess I’ll check the injectors first by disconnecting each one at a time to see the effect, thanks Mohawk ! - but then it’s airbox and throttles bodies off - again ! 😬. I’ll report back ......

Link to comment
Share on other sites

  • Member Contributer

I agree with Mohawk... I suspect an air leak... on a fuel injection system any air that gets
past the throttle bodies the map adjust with the corresponding amount of fuel and the

result is high unwanted idle...

 

 Make sure all the rubber hoses are connected and in good shape... make sure all the intake boots are
tight and in good flexible shape... if the rubbers are hard and cracked its time for replacement...

 

Link to comment
Share on other sites

Thanks all, so today I ran a test. Fired her up, and in turn blocked off the top of each main air intake - 2,3 & 4 all yielded the same result, the engine slowed noticeably. However no. 1 when when blanked off made no difference to engine idle speed but she started to pop and bang .....so  I am assuming then an air leak below the throttle discs somehow on no. 1 cylinder. I cannot find anything obvious, cracked or split hoses etc so ive disassembled the starter valve and all good there too !! the little pistons all stop airflow completely. Interesting that the ‘fixed’ starter valve is no.1. cylinder.....

 

I have notice though that the rubber boots are quite hard and inflexible although they look in good shape so why no.1 should leak I don’t know . I expect Honda will charge me an arm and a leg to replace those .....

 

 

Link to comment
Share on other sites

  • Member Contributer

Its a good idea to perform preventive maintenance anytime you have
accesses under the throttle bodies..

 

Mr.RC45 at 50K miles mark before and after...

 

gallery_3131_51_14104.jpg

 

gallery_3131_51_61992.jpg

 

Not only were all the throttle bodies boots replaced all the hoses and
O rings were also replaced for obvious reasons...

 

gallery_3131_51_51755.jpg

Link to comment
Share on other sites

  • Member Contributer
5 hours ago, Thirls said:

Thanks all, so today I ran a test. Fired her up, and in turn blocked off the top of each main air intake - 2,3 & 4 all yielded the same result, the engine slowed noticeably. However no. 1 when when blanked off made no difference to engine idle speed but she started to pop and bang .....so  I am assuming then an air leak below the throttle discs somehow on no. 1 cylinder. I cannot find anything obvious, cracked or split hoses etc so ive disassembled the starter valve and all good there too !! the little pistons all stop airflow completely. Interesting that the ‘fixed’ starter valve is no.1. cylinder.....

 

I have notice though that the rubber boots are quite hard and inflexible although they look in good shape so why no.1 should leak I don’t know . I expect Honda will charge me an arm and a leg to replace those .....

 

 

Is the boot clamp tight for number 1?

Link to comment
Share on other sites

  • Member Contributer
On 12 May 2020 at 8:52 PM, Mohawk said:

If not the wax unit, it will most likely be an air leak.

Check the throttle butterflies are closing all the way. They are NOT used for the idle cycle, which is what causes the sudden lurch from idle to initial throttle!

If you can get something to block all four air intakes, then block one at a time first whilst bike idles & see if the idle drops on any particular one.

You could try some grease to seal the butterflies or squirt some quick start into each intake in turn & check the result. You can also squirt it at the intake boots & vacuum tubes under the throttle bodies & see if the engine picks up.

 

Check that the flapper valve vacuum tube is connected &/or blocked off correctly, same the the MAP sensor hose at rear right of lower airbox half.

I assume you have adjusted the idle screw ? It's on the right side of the throttle body next to the starter valves, accessed via a small hole in the right frame rail covered with a rubber bung if it there.

Also the starter valves can leak, squirt some quick start or WD40 around them, as the O-rings n=may have perished without use, they are 20 years old.

 

If you want to check the injectors, just disconnect one at a time & the result should be the same for all four.

 

Let us know how you get on.

 

That's a great lot of good advice there Mohawk, I will remember these good pointers, for my own future reference.

Hope your COVID-19 recovery is going well.

Best Regards.

Link to comment
Share on other sites

  • Member Contributer
9 hours ago, Thirls said:

 

 

I have notice though that the rubber boots are quite hard and inflexible although they look in good shape so why no.1 should leak I don’t know . I expect Honda will charge me an arm and a leg to replace those .....

 

 

All the TB boots I've removed have been like that - they're not particularly pliable or "squishy" - they've been hard but with some pressure can be squeezed slightly in to an oval then will rebound to shape.  Once cleaned up there should be no visible cracks or splits.  If not then they're likely OK -  if it's the TB boot leaking it must not be tight.  Honda gives a spec for that tho how in the world they expect us to measure that under the throttle body is beyond me. The other thing to be sure of is that both boots and TB are seated completely prior to tightening the clamps.  Honda specs putting a bit of oil on them when installing - probably necessary to get them to seat completely.

Link to comment
Share on other sites

Thanks Mohawk and Cogswell. And Have a wheelie nice day, yup I had already replaced the thermostat, and stubby hoses and cleaned everything up underneath the throttle bodies. When I disassembled it all again this time searching for the air leak, I noticed that a couple of the screws which tighten the jubilee type clips were no longer tight, but in honesty I am not sure how much they do anyway ! The boots seem so tight over the TB’s anyway ! So with no obvious air leaks found I guess my next steps will be to replace all the vac hoses under the TB’s and may change the screws in the jubilee type clips from Philips heads to hex or torx so I can get some decent torque on them, we all know how difficult they are to get to !!

 

I would still like to know why no.1 cyl did not drop the rpm when I blocked the air intake (assume it’s getting enough air via a possible leak below the throttle butterfly disc) and why only why that cylinders started to pop and band kind of ‘softly’ when blocked - the other 3 cylinders did not, they just caused a drop in rpm which I assume is what you would expect. I am desperately hoping there isnt something more sinister wrong with no.1 - e.g. no compression ...... not seen any info that suggests these engines have such an issue though...... 

Link to comment
Share on other sites

  • Member Contributer
6 hours ago, Thirls said:

I noticed that a couple of the screws which tighten the jubilee type clips were no longer tight, but in honesty I am not sure how much they do anyway ! The boots seem so tight over the TB’s anyway !

Why not just tighten those loose clamps and be confident they are sealing properly? Then re assess the situation. You never know, it could be that simple! Just a thought!

Link to comment
Share on other sites

  • Member Contributer

While not related to the high idle problem,  #1 cylinder not causing an rpm drop could be from either spark or fuel delivery issue.  Those are not likely,  but it never hurts to make a thorough inspection before drawing conclusions. 

Link to comment
Share on other sites

So I’m no further with a resolution to this yet in terms of finding any air leak path. I have found another long thread on here which all sounds very familiar, which turned out to b a bad TPS, as below, so that is my next investigative route . I’ll report back....

 

Link to comment
Share on other sites

Finally I have found the root cause, so the throttle disc to bore interface has some ‘molybdenum sealant’ on it, mine are quite badly chipped so air leak path passed the closed throttle discs - see photo ! I blocked off the main air intake stacks completely so that the idle bypass valve was the only route for intake air and sorted - idle of around 1200rpm ! Now I need to find an aftermarket service to refurb my throttle bodies - any UK riders know of such a company ?? Thanks all for suggestions, ideas along the way but chuffed I at least know the problem is caused by now !

 

7311EEF5-F97A-4D91-A598-B1CA9536AD82.jpeg

Link to comment
Share on other sites

Glad you found it, I haven't heard of any companies that refurb the throttle bodies in the UK

There are a number of them on ebay, something like this https://www.ebay.co.uk/itm/2000-Honda-VFR-800-F-Throttle-Bodies/172949010675?_trksid=p2485497.m4902.l9144

 

may be a simpler/quicker option, maybe just ask for some good photos of the throttle disks?

Link to comment
Share on other sites

  • Member Contributer

Great find Thirls, clever method in discovering the air leak. Certainly one to remember. Good luck with sourcing the new TB. Keep us posted.

Link to comment
Share on other sites

  • Member Contributer

Is the 'sealant' something someone added?  I can't recall seeing anything like that previously.

Link to comment
Share on other sites

  • Member Contributer
26 minutes ago, Cogswell said:

Is the 'sealant' something someone added?  I can't recall seeing anything like that previously.

Hi Cogswell.

It's definetly a Honda thing. See attached.

Service Manual also warns of using commercial "Carburetor cleaners" inside the bores which could damage the Molybdenum Coating.

 

 

image.png

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.