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Author Topic: Engine idling erratically  (Read 2922 times)

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Engine idling erratically
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Hi guy's. Had my 2005 MT01 for over 100,000 kms, 13 yrs, with little trouble. However, gradually, over the last few months there has been a slow increase in an idling problem. Symptoms are:
Idle engine speed revving low till nearly cutting out, also revving to 1200 rpm, all this just waiting at traffic lights.
Engine not starting when trying to re start after a few km's, like when stopping for fuel and engine is at running temp. Engine finally starts after turning off ignition, turning it back on, holding throttle wide open and pressing the starter. Then runs like a pig for a minute.
I have run this bike with a Power Commander IV for years but disconnected it as to eliminate it from the equation. Now running on standard electronics. Symptoms are still there albeit slightly worse.
I have sealed any leaks in the exhaust system, checked any splits in all rubber piping under the tank and behind the covers.
Replaced all spark plugs.
Checked intake rubbers for deteriation, all good
Had the TPS tested, the resistance does drop out briefly, which, I'm assuming, created a flat spot around 2000 rpm, I have altered the position of the TPS a few times moving this flat spot around. Works well but then idles way too high causing the engine to get really hot at standstill.
All things point to a dodgy TPS, gradual deterioration over months, erratic idling etc.  Air temp sensors may be the problem too. Has anyone had this problem or could pinpoint the culprit. I'm trying to eliminate all possible causes before parting with dollars. Any help would be appreciated.
Bike runs great above 3000rpm. I love this thing ;D

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Re: Engine idling erratically
« Reply #1 on: »
TPS around £120 pounds so worth changing as you think it's faulty anyway

Re: Engine idling erratically
« Reply #2 on: »
Thanks Rocker, looks like I may have to do that. Currently running it with a tank full of injector cleaner. If I fix it I'll be one happy bunny. ;D

Re: Engine idling erratically
« Reply #3 on: »
New TPS fitted and set up according to the manual, no change. Feels like the old air leak problem with carburretors, hunting and hesitating at quarter throttle. Hmmm, not giving up  ;D

Re: Engine idling erratically
« Reply #4 on: »
Did you check the valve clearances?

Re: Engine idling erratically
« Reply #5 on: »
Are you running a stock exhaust it could be the O2 sensor given up the ghost at 100000 km down load the manual and run the checks

Re: Engine idling erratically
« Reply #6 on: »
Thanks for the replies,guys. Yes valve clearances are to spec, O2 sensor, could be.I'll check any settings Its quarter throttle and below where the problem is. 2100 rpm and above and the bike flies. Idle erratic and what seems a bad flat spotup to 2100rpm.

Re: Engine idling erratically
« Reply #7 on: »
Sounds like a weak mixture are the intakes ok ?

Re: Engine idling erratically
« Reply #8 on: »
Hi Rocker, First thing I suspected, this fault has declined gradually over 6 months.intake rubbers look ok but any cracks could cause the same symptoms. Not pulled apart the intake as yet but it's on the list as the elimination process continues.I use the bike every day for work etc so this weekend will be full on with fault finding.
Thanks for the input . This is one of those niggly, frustrating problems that could be one thing or a combination of a few things.

Re: Engine idling erratically
« Reply #9 on: »
Hi!
I have the same problem and I was going to adress it these days...
Have you found a solution?

Re: Engine idling erratically
« Reply #10 on: »
Hi Corben, no solution as yet. I'm spending too much time at work to get stuck into the bike properly. I do use it every day as it is rideable although a pain in the ass when trying to accelarate from the lights and even overtaking.Read through the suggestions already posted in this thread, it may help. If I find the solution I will gladly post it on this site. One other thing I've found is that the air intake flapper is constantly open, the air pipe connected to it does not suck and the engine does not change tone when this pipe is connected or disconnected. This could be an idle control unit problem also. Fun times.  :)

Re: Engine idling erratically
« Reply #11 on: »
Hi Corben, no solution as yet. I'm spending too much time at work to get stuck into the bike properly. I do use it every day as it is rideable although a pain in the ass when trying to accelarate from the lights and even overtaking.Read through the suggestions already posted in this thread, it may help. If I find the solution I will gladly post it on this site. One other thing I've found is that the air intake flapper is constantly open, the air pipe connected to it does not suck and the engine does not change tone when this pipe is connected or disconnected. This could be an idle control unit problem also. Fun times.  :)

Not been on the forum for a while and there is lots to read.
I reckon that you might need to give the idle control system a strip and clean.
That line you mention for the flapper is nothing to do with it. IMHO, block the end of it with a small bolt and leave the flap open. It is opened at certain speeds by the ecu.
The idle control is a system that draws air from inside the airbox into the ICS and then into engine. By varying the amount of air that bleeds through the idle is regulated. The bit of hunting it gets while warming up is the ICS cutting the air supply and seeing if the engine speed drops too much whereby it puts a little more air in to speed it up. It could just be sticky and the way it has developed supports that. Its behind the header side top engine mount.
Have you put a new air filter in recently, silly I know but have you? K&N are great. Is the ecu standard? The pc is pointless if it is.

Re: Engine idling erratically
« Reply #12 on: »


Not been on the forum for a while and there is lots to read.
I reckon that you might need to give the idle control system a strip and clean.
That line you mention for the flapper is nothing to do with it. IMHO, block the end of it with a small bolt and leave the flap open. It is opened at certain speeds by the ecu.
The idle control is a system that draws air from inside the airbox into the ICS and then into engine. By varying the amount of air that bleeds through the idle is regulated. The bit of hunting it gets while warming up is the ICS cutting the air supply and seeing if the engine speed drops too much whereby it puts a little more air in to speed it up. It could just be sticky and the way it has developed supports that. Its behind the header side top engine mount.
Have you put a new air filter in recently, silly I know but have you? K&N are great. Is the ecu standard? The pc is pointless if it is.
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Thanks Omeo, will do what you suggest, It was on the list and sounds a simple elimination. I'm running the bike on standard ECU at moment, Standard air filter.