Cylinder misfire

[MNFJR]

This has likely been covered somewhere, but I'm unable to find anything through searching.

In May of this year I had the TPS on my 05 replaced by a dealer under the recall .

Shortly afterward I began to notice an intermittent misfire in one of the cylinders. More noticeable at idle and much less at higher rpms.

I decide it wouldn't be a bad idea to do a TBS, since I hadn't yet this season.

What I am finding is that the #s 2, 3 & 4 are reading right around 250 mm hg, where they should be, while #1 was at about 100. I was able to move it up about 10mm before the screw bottomed out, and so I can't get is anywhere near the other three.

Any ideas on what might be going on here?

Only 11,000 + miles on this bike.

Thanks in advance for the help.

 

[madmike2]

IIRC, 1 & 3 fire together from the same coil. Did you check the sparkplug lead on #1? Check the plug?

Listen for "the dreaded tick? J/K

 

[un4gvn]

Low compression?

 

[kaitsdad]

Either spark or a vacuum leak.

Here's an earlier post about a vacuum leak - Wonky's Vacuum Adventure

While I doubt that it's anything related to what the problem ended up being - the post does list some methods of diagnosing a vacuum leak that work very well.

 

[HYCLE]

This has likely been covered somewhere, but I'm unable to find anything through searching. In May of this year I had the TPS on my 05 replaced by a dealer under the recall .

Shortly afterward I began to notice an intermittent misfire in one of the cylinders. More noticeable at idle and much less at higher rpms.

I decide it wouldn't be a bad idea to do a TBS, since I hadn't yet this season.

What I am finding is that the #s 2, 3 & 4 are reading right around 250 mm hg, where they should be, while #1 was at about 100. I was able to move it up about 10mm before the screw bottomed out, and so I can't get is anywhere near the other three.

Any ideas on what might be going on here?

Only 11,000 + miles on this bike.

Thanks in advance for the help.

Here are some thoughts.

Make sure it is not your test equipment, swap hoses from one cyl to the other and see if the low reading is related to the Manometer and not the bike.

Check for vacuum leaks at the intake manifold and injector seal. You can use a propane torch (not lit) to spray propane at the manifold and see if rpm increases. You can use carb cleaner but propane is safer and wont damage plastic parts. We have a smoke machine that would blow smoke into the intake and see if it leaks out at a gasket or seal.

Also since your right there at the plugs, try switching spark plugs from number one to number 4 and see if the problem moves with the plug.

Since you mention the miss is worse at Idle and vacuum leaks are more critical at idle I would start looking there.

I hope this helps.

Mike

 

[v65]

(not lit)

Takes a bit of the excitement out of the process! :lol:

 

[radman]

1) A miss will not affect a vacumn reading during a tbs. You are measuring throttle blade opening and restriction to cylinder pumping-a purely mechanical function. You could remove all 4 plug wires, and if you could turn the engine over at 1100 rpm, the cylinders would all read in the neighborhood of 240hg. A TBS simply sets the throttle blades to attempt to equalize the four cylinders to run as one, smoothing vibrations and improving cylinder balance.

2) An adjustment to the throttle shaft balancing screw at the junction of #1 and #2 could be what fixes this, similar to The Unauthorized TBS, reprinted here for your benefit.

Copyright 2004 Arlen Bloom
The Unauthorized Throttle Body Synchronization Procedure

There has been a lot of interest in the Throttle Body Synchronization Procedure lately, with a new generation of Waiters finally taking delivery of their 2005 FJR’s, so I thought it timely to discuss the procedure recommended in the service manual as well as another I used to synchronize the bike at highway speeds as well as at idle.

My motivation for seeking an alternative procedure came when I found all four throttle bodies synced at idle, and all but one synced at 4200 rpm. Many FJR owners complain of excessive vibration or buzz in the handlebars between 4000 and 4500 rpm and I thought synchronization at an engine speed we spend more run time at might eliminate a good portion of that. The service manual only illustrates syncing at idle, but in theory, everything should also work in unison at 4200 rpm. To confuse things more, the manual also says to NOT adjust the butterfly adjusting screws and does not include any information on how the throttle body assembly actually works. In fact, if you need to replace certain throttle body parts, the parts diagrams indicate you would have to order a complete throttle body assembly! I decided it was time to unravel some of the mystery about throttle body adjustments.

So How Does the Throttle Body Assembly Work?

The purpose of the throttle body assembly is to mix fuel and air and introduce that mixture to the combustion chambers via the cylinder head. It is important for the airflow in all throttle bodies to be equal so that each cylinder carries its share of the load and does not create an engine that runs rough, hot, or too rich or lean. Equalizing the airflow is accomplished by performing the synchronization procedure.

Carburetors mix airflow with fuel, but throttle bodies only control airflow. While carburetors use slides to change airflow above idle, throttle bodies use butterfly valves. At idle, airflow is to be adjusted with air screws.

The FJR uses its #3 throttle body as a baseline to which the other throttle bodies are synced. In addition to the air screws, synchronization is affected by:

the initial vacuum setting of the #3 throttle body

the mechanical adjustments between throttle bodies

idle speed

interference of idle speed by throttle stop screw adjustment or throttle cable adjustment

any vacuum leaks between the air box and the throttle bodies, or between the throttle bodies and the cylinder head

Throttle stop screws are adjusted to set the minimum idle speed that can be achieved by turning the idle adjustment screw. Butterfly sync screws adjust the butterfly openings of adjacent throttle bodies so they have the same amounts of airflow at a given engine speed above idle. Air screws bleed off a small amount of vacuum to adjust the amount of airflow to equal that of throttle body #3 at idle.

Synchronization By-the-Book

Let’s start with the synchronization procedure that everyone has been doing up to now. The steps are modified a bit to tie it all in with the Unauthorized Synchronization covered later. You will need a long, thin-bladed screwdriver to adjust the air screws, a vacuum gauge, and a carburetor synchronization tool. I use a TwinMax electronic meter, but a mercury stick or Morgan Carbtune will allow you to look at the vacuum readings of all four throttle bodies at once and eliminate a lot of hose-switching between adjustments.

After warming your engine up to at least two bars on your bike’s graphic display (while avoiding exposure to carbon monoxide) and raising the gas tank to access the throttle body area, follow these steps:

Adjust the idle speed to 1000 rpm using the idle adjusting screw found on the right side of your bike. This would be just inside your right knee if you were sitting on your bike.

Find the appropriate vacuum port for throttle body #3 and remove the little rubber cap. Connect the vacuum gauge hose to the vacuum port and place the gauge where you can easily read it while making adjustments to the #3 air screw.

Adjust the #3 air screw until you read 9.8” Hg (+ 1” Hg per 1000 ft. above sea level). You may need to restrict the vacuum hose to keep the needle from jumping around. Check your idle speed again and readjust until both adjustments are attained simultaneously.

Remove the vacuum gauge hose and attach the carburetor synchronization tool to vacuum port #3 and one of the other vacuum ports. (All three if you are using a 4-hose tool.) Note which hose is connected to #3.

Turn the air screw(s) to adjust the vacuum at each throttle body to match that of #3. All four throttle bodies should be within .4” Hg. Check your idle speed again after adjusting each air screw and readjust vacuum and idle adjustments until both are attained simultaneously.

With the hoses still attached, use your throttle to increase engine speed to 4200 rpm and see if your gauge still indicates synchronization. If they all look good, you do not need to go any further. Otherwise, you may want to perform the Unauthorized Synchronization Procedure.

Synchronization Without Authorization

I have given this procedure a rather ominous name because I want to impress upon you that this is serious business. As it is not covered by the Yamaha service manual, this is uncharted territory (until now anyway) and if you are all thumbs when it comes to mechanics, you should put down your tools and step away from your bike. This method of synchronization is one that must be done meticulously and from the first step through the last. Having a brain fart or nervous breakdown in the middle of it is not acceptable! If you were to screw up the idle speed synchronization in the previous section, it is no big deal. Your bike will still start and run and you may not even realize you screwed it up. But if you screw THIS up, you WILL know it. Chances are real good your idle speed will not adjust to lower than 1300 rpm. And it goes down hill from there! If you do this procedure, it is YOUR decision and YOU suffer the consequences! I take NO responsibility for YOUR actions!

You still with me? Good. I just have to make it sound scary to chase off those who shouldn’t even be reading this, let alone jumping in with a screwdriver. Be aware, however, that we will be messing with painted screws and it is uncertain whether they were painted to keep them from turning or to indicate when some idiot messes with them. My logic is that Yamaha doesn’t plan on doing anything warranty-related with throttle body adjustments, but if they aren’t in sync at the speed you normally ride, it is required that something be adjusted. So come on lemmings! The cliff is this way!

In addition to the tools you used for the idle speed synchronization you will need a cross-tip screwdriver, 8mm combination wrench, and a 2.5mm hex wrench. Make sure your idle speed sync has been done with reasonable success, and your gas tank is raised for access to the throttle body area. This may take some time, so consider pointing a fan at the front of your bike to help keep it from melting. And don’t expose yourself to a carbon monoxide poisoning situation! Now follow these steps:

Adjust your throttle cable at the grip so there is a small amount of slack. We don’t want the cable to interfere with our idle speed when we are making critical adjustments.

Back off the idle adjustment screw until idle speed quits dropping. This will show us the minimum idle speed and it should be about 750 rpm. Don’t get carried away, if you go too far the screw will fall out and you will be on your own.

Look at the painted throttle stop adjustments. These are the pairs of small hex socket set screws with lock nuts located between throttle bodies #1 & #2 and #3 & #4. The levers connected to the butterfly valves bump up against these stops at their minimum opening. All four levers should touch their stops at the same time and the idle speed should be 750 rpm. Close any gaps by adjusting each stop screw until it just touches the lever. If idle speed is above 750 rpm, you will probably see a gap between one or more of the levers and their stop indicating a throttle body is out of sync. Back off each of the four stop screws by small amounts until idle speed drops to 750 rpm. If idle speed is below 750 rpm, adjust the stop screws to increase the idle. Adjust them by loosening their lock nuts and using the hex wrench to turn the screws then tighten the lock nuts. To gain enough clearance for my combination wrench, I removed the two screws for the fuel rail and took out the aluminum standoffs. Grinding a flat spot on each standoff allowed me to get my wrench over the lock nuts. Next time, this won’t be a problem. Be careful not to cut the little injector O-rings when reinstalling the fuel rail.

Boost the idle speed back up to 1000 rpm using the idle adjustment screw. This idle speed is very important and should be maintained after any other adjustment is made. Make an adjustment, readjust your idle speed, then check the new adjustment again until the adjustment and the idle speed are both where they should be. This applies to every step throughout the entire procedure from this point on.

Adjust the vacuum on throttle body #3 for 9.8” Hg (+ 1” Hg per 1000 ft. above sea level) using the #3 air screw. This screw should not be touched again! Throttle body #3 is our reference point and we have just set the base line. Leave it alone from this point on! Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment.

With your carb sync tool attached and throttle speed increased to 4200 rpm, adjust the butterfly sync screw between throttle bodies #3 & #4 until the vacuum on #4 equals that of #3. These painted screws have cross-tip heads and springs on the shafts. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment. Also make sure the throttle stops do not touch the butterfly valve levers.

Sync throttle body #4 to throttle body #3 at idle by adjusting the #4 air screw. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment.

Compare the vacuum of throttle body #1 to the vacuum of throttle body #2 at 4200 rpm and adjust the butterfly sync screw between them to make the vacuums equal. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment and make sure the throttle stops do not touch the butterfly valve levers.

Sync throttle body #1 to throttle body #3 at idle by adjusting the #1 air screw. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment.

Sync throttle body #2 to throttle body #3 at idle by adjusting the #2 air screw. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment.

Sync throttle bodies #1 & #2 to throttle bodies #3 & #4 at 4200 rpm by adjusting the butterfly sync screw between throttle bodies #2 and #3. To make this adjustment, you will have to shut off the motor and twist the throttle grip until the butterfly sync screw is accessible with your screwdriver. It will probably take you about three repetitions to make the adjustment. Use the idle adjust screw to make sure your idle speed is 1000 rpm throughout this adjustment and make sure the throttle stops do not touch the butterfly valve levers.

Sync throttle bodies #1, #2, & #4 to throttle body #3 at idle by adjusting the respective air screws. Make adjustments to the idle adjust screw after each air screw adjustment to ensure that idle speed remains at 1000 rpm.

Compare the vacuum readings of all four throttle bodies at 4200 rpm to see if they are within .4” Hg of each other. If they are, your throttle bodies are now completely synchronized and you are finished. If not, go back to the beginning of this section and perform the procedure again. It is not uncommon to have to go through the procedure one or two more times as the synchronization of the throttle bodies is very, very dependent upon idle speed and every adjustment you make along the way affects the idle speed. If you do one step with the idle speed at 1000 rpm and two steps later you make an adjustment when the idle speed has varied by as little as 50 rpm, this method cannot be completed successfully. But the second time you go through the procedure, all your adjustments will be much smaller than the first time and the idle speed won’t be affected as much. This will make your subsequent adjustments more precise and throttle body nirvana will be achieved. While it is possible to sync all throttle bodies within .4” Hg at both 4200 rpm and 1000 rpm, it is ultimately up to you to decide what level of accuracy you want to achieve. In the end, however, I think you will find that this method is effective at reducing at least some of the vibration formerly experienced between 4000-4500 rpm. Keep in mind, though, that there are other things that could also cause that same vibration; this just deals with one of those causes.

3) If this does not solve the issue, you have a mechanical fault internally, such as a vacumn leak, like Kaits suggested, or a sticky valve, or bad piston rings, the least likely of the possible scenarios.

 

[Bustanut joker]

Shit drank ten beers just reading that info Can't imagine how I'm supposed to actually attempt it after downing that many

tanks fer the repost Radman

:jester:

 

[MNFJR]

Thanks for all the feedback everybody.

Radman,

I considered doing the "unauthorized" TBS prior to starting this thread, but was a bit nervous about it, so I went with the authorized.

A couple of questions for you:

Could a vacuum leak be causing the missfire?

Is this problem something that I could expect to be covered under Y.E.S?

Perhaps I am just as well off if I take it in and let the dealer sort it out.

Thanks

 

[radman]

Could a vacuum leak be causing the missfire?

Yes. A big enough vac leak will cause a lean condition in the affected cylinder, as the fuel delivery assumes certain conditions that no longer exist in that hole.

Is this problem something that I could expect to be covered under Y.E.S?

Possibly, depends on what the actual cause is. A TBS is not covered, only hard faults and parts replacement, as well as some diagnosis.

Perhaps I am just as well off if I take it in and let the dealer sort it out.

You may end up doing that anyway, why not try and determine the cause first, and learn something in the process? While I can't understand what, in the process of a TPS replacement, would cause a cylinder to be adjusted to the point where it's contribution to power output is almost nil, it's possible the tech played with the throttle body alignment and put #1 well outta whack-won't hurt to attempt an adjustment, noting it's position before beginning adjustment should you find it's not helping the situation and wanting to return it to it's pre-adjustment state. Symptoms, however, point to something having gone whacko on 1, though, and this is what I'd be doing to try and bring 1 back on line, so to speak. Open 1's idle air screw to 1/2 turn out, and see if adjusting the shaft screw works. Turning the left shaft screw CLOCKWISE will bring it's vacumn up, while at the same time reducing #2's reading. PM me your email address, I'll send you a handy guide to simplify the process.

 

[PA1195]

Could a vacuum leak be causing the missfire?

Yes. A big enough vac leak will cause a lean condition in the affected cylinder, as the fuel delivery assumes certain conditions that no longer exist in that hole.

Is this problem something that I could expect to be covered under Y.E.S?

Possibly, depends on what the actual cause is. A TBS is not covered, only hard faults and parts replacement, as well as some diagnosis.

Perhaps I am just as well off if I take it in and let the dealer sort it out.

You may end up doing that anyway, why not try and determine the cause first, and learn something in the process? While I can't understand what, in the process of a TPS replacement, would cause a cylinder to be adjusted to the point where it's contribution to power output is almost nil, it's possible the tech played with the throttle body alignment and put #1 well outta whack-won't hurt to attempt an adjustment, noting it's position before beginning adjustment should you find it's not helping the situation and wanting to return it to it's pre-adjustment state. Symptoms, however, point to something having gone whacko on 1, though, and this is what I'd be doing to try and bring 1 back on line, so to speak. Open 1's idle air screw to 1/2 turn out, and see if adjusting the shaft screw works. Turning the left shaft screw CLOCKWISE will bring it's vacumn up, while at the same time reducing #2's reading. PM me your email address, I'll send you a handy guide to simplify the process.

I think what I found in my synch'ing is the same as you've stated above in a bit different way: turn the shaft screw towards the high vacuum throttle body to reduce the vacuum reading at, for example, cruising RPM's...for example, if #1 is hign, turn the #1/#2 screw CCW towards #1 maybe 1/ 8 turn and check if #1 decreases...if #4 is high, then turn the screw CW towards #4 and it should decline...as for #'s 1/2 vs. 3/4, I don't recall and trial and error was the result...there has to be a vacuum leak on MNFJR's #1...vacuum line to the Intake Sensor, test port cap bad or missing, TB to engine seal loose...mine missed badly at 3500 when my Morgan Carbtune hose pulled off of #1 while doing the proceedure last week...now off to the local IM station for a CO read with the Barbarian Mod at different +- levels.

Gary in Fairbanks

 

[tiiikeri]

I had the same problem with my previous FJR ´03 ABS.Those values were pretty much same for me. #1 cylinder vacuum was way out of specs and couldn´t adjust with the normal adjusting air screws. That happened after my bike was serviced by Yamaha dealer...

I noticed this problem when I was checking TBS after that service. Just wanted to check that the dealer have adjusted TBS correctly...I was glad I did...

Well, the solution for the problem was simple...There is the cold starting system in #1 cylinders throttlebody (under the air screw). That cold starting system was jammed open, because there was wires between the system and the # 1 throttle body(the dealers service did do this accidentally).The cold starting system couldn´t close and operate normally because of those wires when the engine was warmed. So I removed those wires and zip tie them to their original position in the wiring harness. Then checked the TBS with Morgan Carbtune. Everything was fine after that.

Just check the cold starting system, hope it is the answer...

Hope your solution is as simple as mine was.

 

[MNFJR]

tiiikeri

Thanks for the info. Certainly sounds similiar, although you don't mention whether yours was running poorly as mine is.

Anyway I appreciate the help. I'm off today and will spend some time trouble shooting.

MNFJR

 

[ionbeam]

Another simple thing to check is to verify that the plug wire caps are fully seated on the plug. For some reason my #3 plug wire kept popping off the plug. The cap looked ok, and when touched casually seemed ok but when pressed down I could feel it click back on. Night and day difference after that little click.

 

[MNFJR]

Okay,

So I've ruled out a vacuum leak and the cold starting system being jammed open. For grins I replaced the spark plugs while making sure the wires are securely attached.

Call me a wimp, but I'm reluctant to do the unauthorized TBS.

Seems to me if I can't do this conventionally, then it is a problem that should be covered under warranty.

Also, I now realize that I am hearing a sound that is frighteningly similar to the ticker audio that is provided at the top of this forum. While mine is not as loud, it sounds very much the same.

I'm calling the dealer.

Thanks again

MNFJR

 

[T-man]

Almost sounds like a valve issue. Had a car once with very similar issues. I threw a lot of parts at it trying to fix it, then someone told me to do a compression check. Ended up being a burnt valve. Now I always do one before spending money on parts. Hope it's not a ticker issue. Let us know what you find out.

 

[Constant Mesh]

When the dealer's tech changed out my TPS he unbolted the airbox so he could move the throttle body assembly up/away enough to allow him to access the TPS's lower mounting bolt. If your tech did this as well he might have somehow created an air leak at TB1 or between TB1 and the engine.

 

[ELP_JC]

I was betting on a vacuum leak, but you said you ruled it out. Check Mesh's suggestion, as with an engine with that few miles, I REALLY doubt it's a valve, or one of the other more serious issues.

If still no vacuum leak, check the TB plate adjusting screw (#1/#2); I'd bet the paint is gone, meaning it was messed with before. If that's the case, why not attempt adjusting it properly? You'd get charged for it anyway and NO dealer will know how to do it properly, as there're no instructions. The TB adjusting screws are very different from all other bikes; I've done a bunch, and never seen something like the FJR. Just mark everything before starting, so you can put it back together in a minute; no harm trying, and you already have the synch tool. Nice way to bond with your baby on Sunday < he he>. Good luck.

JC

 

[PA1195]

I was betting on a vacuum leak, but you said you ruled it out.

JC...I thought you got pissed and moved to the Dark Side...good to see you're still here doing your thing.

Gary in Fairbanks