05 Poor Idle When Cold

[NorthernRider]

Pretty much what the title says, 05 FJR with 36k miles that idles rough (or at least what I consider to be so) at start up. RPM will fluctuate 500 RPM and every once in a while there is a sound of a mechanical clunk/miss fire. Once it's got a bar or two on the temp gauge it smoothes out considerably but still a slight stumble to the revs. I got this bike with roughly 32000 on the clock and it's done this since I've owned it. Valve clearances where checked and adjusted 1500 miles ago as well new spark plugs and air filter. Throttle body sync was performed using a morgan carbtune. Tonight I did the barbarian jumper mod and bumped all CO settings up 7 points but to no avail. At this point I'm not sure what to look at next, fuel pump/pressure, coils, vacuum leaks. etc. What do you all think?



Thanks,

Chris

 

[Geezer]

I was going to suggest plugs and air filter, but you've already done that. The next thing I'd try is some injector cleaner, specifically Seafoam, in the tank and see if it clears things up after it runs through and you refill with fresh fuel.

 

[lele]

I have got the same symptoms last year in my bike...

I think your fuel is not fresh or maybe there is some nafta in there

 

[Fred W]

Thanks for the video. If a picture is worth 1000 words a video is worth 10,000.

From memory, your cold idle speed seems about right (~2k rpm), so the cold start wax motor mechanism of the throttle bodies seems to be working OK to raise the idle speed (added air). The only thing that is worrisome are the larger dips, which seem to be due to some misfiring. My guess would be this is due to improper cold start fueling since it goes away when warmed up.

Do you have a PCIII on the bike? If so, that is actively modifying the fueling when warm or cold, so try eliminating that first.

Is the O2 sensor still hooked up? If so, that may explain why the warm idle (when the O2 sensor is active) is better than the cold idle before the sensor comes up to temperature.

The stumbling may be due to a small vacuum leak that is being masked when warm by the O2 sensor.

The engine is more susceptible to lean stumbling when cold, plus the O2 sensor may also be masking that to some degree.

It could also be one of the temp sensors feeding the ECU causing the fueling to be a bit too lean, especially at lower temps.

You can go through all of the onboard diAG sensor displays and see if everything looks OK.

 

[ionbeam]

FWIW --->

Warmed up idle speed needs to be set to 1,100 RPM.

Confirm that the 10k resistors in the plug caps are good, they sometimes oxidize and the value goes up significantly. Secondary coil resistance is 12kΩ to 18kΩ, so, putting your DMM probes in two spark plug caps (1 & 3; 2 & 4) you will get: 10kΩ + 15kΩ + 10kΩ = 35kΩ If your readings are over 100KΩ the resistors should be checked.

The fuel system should be cleaned using Yamaha Ring Free, Techron or similar product. The Ring Free will do just that, ensure the rings aren't stuck which the FJR seems prone to as well as cleaning the injectors. After using a cleaner run some straight, unadulterated fuel through the system before continuing the troubleshooting process.

Clip a DMM to the ground and signal wires of the TPS. With a stone cold engine, start it up and watch at the DMM voltage. The voltage should be stable. When the thermostat finally opens, hot coolant should flow past the wax motor on the fuel rail and the idle speed should drop and the DMM should read 0.63 to 0.72 volts and be stable.

Borrow a vacuum hose off of your sync tool for the vacuum restrictor which will stabilize the reading on a vacuum gauge or use one port of the sync tool. Put the vacuum gauge/sync tool on a sync port, start a stone cold engine and watch the intake vacuum, it should be stable, as in not wandering around or jumping. At cold idle speed, the vacuum will be lower and rise to 210 - 250 mm hg as the idle speed drops to a warm idle and should be stable at idle speed, don't sweat the actual reading, it should just be stable. Or, put the sync tool on the four sync ports of a cold engine and start it. The vacuum readings will be low due to the fuel enrichment and high idle speed. If one cylinder has notably vacuum compared to the others it may be an indication that it is much leaner than the others. Swap the injectors and see if the high reading on cold start-up follows the injector, if it does then the injector may have a clogged internal filter or may need professional cleaning.

Anyhoo, these are a few things that can be done/checked. Following these steps in order will help get a picture of what's going on. Depending on your results, they will guide the next troubleshooting steps.

Edit: I see Fred was plowing the same field as I was typing. I will note that the Gen I ECU doesn't see the O2 sensor at cold idle.

 

[Fred W]

Edit: I see Fred was plowing the same field as I was typing. I will note that the Gen I ECU doesn't see the O2 sensor at cold idle.

Yup, that's why I said that it could be masking the problem when the engine is warmed up (if still connected). I never suggested the O2 sensor was a likely culprit. Just getting clues on what his configuration is.

The reason I do not think anything ignition related would be a likely root cause is because it doesn't really matter much to the ignition what temperature the engine is at, and the symptom is said to have gone away when warm.

Also note that the vacuum will fluctuate if you are getting misfiring for any reason (fuel or ignition)

 

[Constant Mesh]

The intake vacuum of each throttle body rises gradually as the wax motor closes the air bypass valve in each throttle body.

If one of the wax motor bypass valves misbehaves a bit and doesn't close in a gradual manner with the others the intake air for that cylinder would be out of sorts with the quantity of fuel injected. The computer gives each cylinder the same amount of fuel assuming that they all receive equal intake air.

If it's idling properly when warm then obviously all of the bypass valves do eventually close properly. They all may not be closing at the same rate as the engine comes up to temp.

 

[Fred W]

The high idle bypass valves are tied together by a single metal link. Not sure how they could open or close other than together.

However, it may be that one or more of the high idle air bypass paths in the throttle body are occluded, which would result in that cylinder running too rich and it's vacuum would be higher than the rest. Still, it would have to be pretty rich to cause misfiring when cold.

 

[Constant Mesh]

I believe the wax motor gizmo opens the air bypass valves but it can't force them closed. Each valve has its own spring which pulls the valve closed as the wax motor mechanism moves to its warm position.

You can view one of these valves in the forum thread below:

https://www.fjrforum.com/forum//index.php/topic/152713-removing-the-throttle-bodies-to-clean-them/?hl=%26quot%3Bwax+motor%26quot%3B&do=findComment&comment=1071735

One can verify if the valves are operating properly using a syncing tool.

Connect the tool to a cold engine. Start the engine and watch each throttle body's intake pressure as the engine comes up to temp. You should see a gradual increase in vacuum as each of the bypass valves close. If a valve is misbehaving, sticking, etc. it will be seen from the comparison of the vacuum profiles.

I recall seeing an account in this forum where someone had moved some components adjacent to the throttle bodies and had left something touching the flex boot on one of the valves. The valve was not closing properly because of this when the engine had warmed. He was having trouble doing a sync with this valve partially open.

 

[NorthernRider]

Thanks everyone for the feedback. Looks like I have a few things to follow up on and will need to bust out the multimeter. Perhaps I was a bit misleading when saying it completely cleared up after warm, at idle it sure is. At 2500 with no load it can be felt/seen to some degree but much much less. Below is a link to a new vid. Hopefully that might give a few extra clues.


I do not have a Power Commander and as far as I know the O2 sensor is hooked up like normal.

Thanks,

Chris

 

[Donal]

Thanks everyone for the feedback. Looks like I have a few things to follow up on and will need to bust out the multimeter. Perhaps I was a bit misleading when saying it completely cleared up after warm, at idle it sure is. At 2500 with no load it can be felt/seen to some degree but much much less. Below is a link to a new vid. Hopefully that might give a few extra clues.

The 'stumble' at 2500 is normal for FJRs. Something to do with the fuel map being very lean (in this area) to help with emissions testing!..............

 

[Fred W]

I'd say that the rpm wavering in the second video at 2500 rpm when warm looks pretty normal.

The stock fueling is pretty lean in that area, which is not one that you normally run the engine at.

All in all, there is not a lot wrong with your bike. Before getting too carried away, you may want to take the advice offered earlier and run a couple of tanks of Seafoam, Techron or (best of the three) Yamaha Ring Free at an elevated dose through it and see if it clears up. You may just have one or more marginally flowing injectors. It is a 12 year old bike, after all.

 

[audiowize]

Yeah, that warmup behavior is all wrong. How does the bike ride?

 

[NorthernRider]

Yeah, that warmup behavior is all wrong. How does the bike ride?

The bike rides wonderfully, this issue doesn't detract from the ride but it nags me.

I finally had a chance to dig into the bike tonight, specifically the resistance of the plug caps and coils.

Cap 1 - 10.88kΩ

Cap 2 - OL

Cap 3 - 10.99kΩ

Cap 4 - 10.29

Coil (2&3) - 14.51kΩ

Coil (1&4) - 14.47kΩ

I could not get a reading on the cap for the #2 cylinder, would a faulty cap read as over limit?

 

[NorthernRider]

Quick update, did some further reading that the caps can be taken apart to get access to the internal resistor, why not give that a try. The resistor itself measured 10.59kΩ. There was however a fair amount of corrosion on the end of the threaded insert that contacts the resistor. Well I took a fine file to that, reassembled and now the cap is measuring in line with all the others. I'll likely take them all apart to clean up prior to putting the bike back together. Fingers crossed it's that easy of the fix.

 

[RossKean]

Hope that's all it is but I doubt that that was the issue. Resistance measured with an ohm meter at low voltage does not predict accurately the effective resistance at the voltage of the ignition system. A very thin oxide coating could be a million ohms at two volts and essentially nothing at 2000 V.

 

[NorthernRider]

Hope that's all it is but I doubt that that was the issue. Resistance measured with an ohm meter at low voltage does not predict accurately the effective resistance at the voltage of the ignition system. A very thin oxide coating could be a million ohms at two volts and essentially nothing at 2000 V.

Your doubts were realized, tank back on and problem persists. Oh well, I'll move on to next suggestions folks had above.

 

[NorthernRider]

I've got a few tidbits of info to add to this thread. Going through the diagnostics there were historic codes (19 and 30) both of which can be accounted for. I was able to test out the injectors and all fired 5 times per the diagnostic check. Now for the odd thing, when I turn the key, let the pump prime as normal and then start it exhibits the poor cold idle. On the other hand, if i turn the key but with the engine stop switch engaged, wait 15 seconds, turn the stop switch back to on the pump will not prime. Start up the bike and it idles noticeably smoother. I thought this might be a fluke but I've tried both ways half a dozen times and in each case not priming the pump prior to starting results in a better cold idle. Thoughts?

 

[Fred W]

Maybe a leaky injector? One cylinder is getting flooded when the rail pressurizes?