Just asking... Are your battery terminals tight and making good contact? Can't hurt to make sure. 
# 4 cylinder
- Thread starter steve'o'
- Start date
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steve'o'
Well-known member
Yeah they are, I just had the dash panels off recently and was hooking my aux lights up and they are tight. This is getting very frustrating, due to the fact I'm not a mechanic, so I have to go through the right channels. It seems like this problem is a hit and miss thing.Just asking... Are your battery terminals tight and making good contact? Can't hurt to make sure.
steve'o'
Well-known member
I really gotta go with Skooter on this one, just a gut feeling. I'm getting a TBS done again to see if #4 is out, and if not I'm getting them to swap #3 injector with #4 injector.
steve'o'
Well-known member
So I've done a few things, a TBS, checked the injector harness and lubed with dialectric grease, checked all 4 plug boots for resistance, all 4 at 10.5 ohms at 20K, snipped off 1/4" of the #4 plug wire just in case of corrosion, did a compression test, came back at 175, switched #3 injector with #4 injector and put in brand new plugs, went for a 2 hr ride at a constant speed of 100-110kph, got home and checked #4 plug, and it was fine, nice and grey like the other 3. Went out later for another quick ride and # 4 is fouled up a bit again, but not as bad as before. BTW thanks Skooter for the info on the injector, #4 did have a bit of crap in it, but it seems #4 cylinder is doing it again, on the #3 injector. So am I now looking at an electrical issue with the coils or is there something else. With a compression test of 175 could it still need a valve adjustment? A wet down test was mentioned to rule out the valves. I was told the original owner did the complete 40,000km check and there is only 57,000kms on the bike now. It just seems when I run it at slower speeds the #4 plugs tends to foul. Any other ideas? BTW 03HiYoSilver how much was it to replace the throttle body? I can only find the whole system which is about $1300-1400.00 :dribble:
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03HiYoSilver
Well-known member
I am sorry to hear that nothing at this point has helped you. When my bike was in for the YES repair... and after many part swaps/replacements, it did come down to the Throttlebody Assy that fixed the #4 fouling condition.
Yamaha YES did pay for it back in '07 and I heard something like $800 but I am not sure if that was cost or retail.
Perhaps you can find a cycle salvage that may help and not sure if other model units are Swappable.
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Mihalis fjr
Well-known member
Try to take out the throttle body 4#
Have a good cleaning on it and have a good inspection on it!
Maybe something there is sticking ore a hole is closing..
Dont buy a new throttle body assy before you check this..
If this is ok,perhaps something going wrong with the fuel management on 4# from ECU..
and if all those are ok..then try to check coils or other electrical parts..
Have a good cleaning on it and have a good inspection on it!
Maybe something there is sticking ore a hole is closing..
Dont buy a new throttle body assy before you check this..
If this is ok,perhaps something going wrong with the fuel management on 4# from ECU..
and if all those are ok..then try to check coils or other electrical parts..
I do not believe that this could be any kind of a coil or HV ignition problem because it would also affect the #1 cylinder as well. The FJR, being a wasted spark design, has to fire the plugs in pairs, and the #1 and #4 plugs are in series on the same coil.
Are you certain that the #4 is still fouling? You did say it doesn't look as bad, and you are certainly sensitized to the condition.
If so, I'd have to go with the #4 intake manifold / throttle body problem theory. But it shouldn't be any sort of a vacuum leak, which is the "normal" failure mode of a worn TB, as a lean condition wouldn't foul plugs. It would have to be the opposite: lack of adequate air. Maybe your #4 throttle body is all gooked up with crud like we've seen pictures of on other folks bikes?
Have you done the Barbarian Jumper Mod on your bike? If so, you could try lowering the CO setting for the #4 cylinder and see if that changes the symptom at all.
You could also try looking at the relative vacuum levels with all 4 of the air bypass screws closed down all the way, both at idle and as you crack the throttle open. That will be an indication of how much air is being allowed (or not) past (or around) the throttle plates. If the #4 throttle plate was closed way down compared to the others, it's vacuum level would be higher, and that cylinder would run richer. Remember, in closed loop mode, the control signals from the ECU to the fuel injectors are trimmed based on the average of all four cylinder in the exhaust stream.
Finally, for the same reason, you could have some vacuum leakage on the other three cylinders which is causing an unnaturally lean condition, sensed by the O2 sensor, and resulting in the one cylinder that doesn't have a leak to run rich.
You might want to fool around with disconnecting the O2 sensor so the ECU never goes into closed loop mode and see what happens.
Are you certain that the #4 is still fouling? You did say it doesn't look as bad, and you are certainly sensitized to the condition.
If so, I'd have to go with the #4 intake manifold / throttle body problem theory. But it shouldn't be any sort of a vacuum leak, which is the "normal" failure mode of a worn TB, as a lean condition wouldn't foul plugs. It would have to be the opposite: lack of adequate air. Maybe your #4 throttle body is all gooked up with crud like we've seen pictures of on other folks bikes?
Have you done the Barbarian Jumper Mod on your bike? If so, you could try lowering the CO setting for the #4 cylinder and see if that changes the symptom at all.
You could also try looking at the relative vacuum levels with all 4 of the air bypass screws closed down all the way, both at idle and as you crack the throttle open. That will be an indication of how much air is being allowed (or not) past (or around) the throttle plates. If the #4 throttle plate was closed way down compared to the others, it's vacuum level would be higher, and that cylinder would run richer. Remember, in closed loop mode, the control signals from the ECU to the fuel injectors are trimmed based on the average of all four cylinder in the exhaust stream.
Finally, for the same reason, you could have some vacuum leakage on the other three cylinders which is causing an unnaturally lean condition, sensed by the O2 sensor, and resulting in the one cylinder that doesn't have a leak to run rich.
You might want to fool around with disconnecting the O2 sensor so the ECU never goes into closed loop mode and see what happens.
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road runner
Well-known member
Also you can lift the tank and use a timing lite to check the spark on all 4. Just watch the lite while on each wire, at idle, and vary the RPM. You want to see a nice consistent flash. If you have a miss fire you will see the lite flicker. This will tell you if it's electrical or not, just make sure you have good plugs in when you do it, because a bad plug will cause the lite to flicker also. If you see #4 miss fire then you could swap coils, just to see, and if that does nothing then you may want to check the crank trigger, reluctor wheel area (not likely but worth looking at).
This way of diag can be tricky, because an over rich or lean mixture will cause a miss fire and the lite can flicker. That's why you need good plugs. A way of checking that is with a KV meter on the plug wires. A coil will bump up the volts to fire a plug so a mixture issue will be seen with that cylinder having a higher voltage going to the plug. For example say #'s 1,2,3 show 20,000 volts going to plugs, and #4 has 40,000 going to it, then that says there's something going on in that cyl.
This way of diag can be tricky, because an over rich or lean mixture will cause a miss fire and the lite can flicker. That's why you need good plugs. A way of checking that is with a KV meter on the plug wires. A coil will bump up the volts to fire a plug so a mixture issue will be seen with that cylinder having a higher voltage going to the plug. For example say #'s 1,2,3 show 20,000 volts going to plugs, and #4 has 40,000 going to it, then that says there's something going on in that cyl.
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My only problem with that test, Art, is it becomes a "chicken or the egg" situation. Is the plug misfiring causing it to foul? or is the plug fouling (for some other reason) causing it to misfire? Like you said, start with new plugs for the best results.
steve'o'
Well-known member
Tks guys. I am due to leave tomorrow at 05:30hrs AST for Laconia. I've packed my CAA card, the FJR forum member list, 4 new spark plugs, and 4 friends I am riding with. Yesterday the problem seemed to be intermitent and after I put 4 brand new plugs in the bike, I did a good ride, and no fouling. It just seems to foul up more at slower speeds, like around town. I guess I'm gonna roll the dice for the trip. Hey you never know maybe one of you fellas may have a 2003 FJR sitting in your yard for sale before the week is out.lol
Mihalis fjr
Well-known member
It listening like a very rich mixture..because the problem is much biger in low speeds..in high speeds the butterflys are much open and the mixture closing to normal..this is my opinion...The problem begin suddenly after the end of winter..I dont think about a electric problem..Something sticking or closing after the winter off period...this i think.
Canadian FJR
Canadian FJR
Good luck and enjoy your trip. Be sure to report any updates.
Canadian FJR
Canadian FJR
steve'o'
Well-known member
So I am back from Laconia, 3300 kms, and the bike worked, good. It seems that while driving on the highway/interstate at speeds of 65-85 mph, the bike works fine. It was when I was caught it traffic going into the rally, sitting at idle that the bike would then "act up" a bit. Once the bike would heat up it would start to make a "clunking" noise which I could also feel in the bars, so while going down hill, I would shut the bike off and coast. After being there for 4 days I pulled plug # 4 and it was fouled a bit, but not like before. So I am still puzzled on the problem. I am getting a "leak down" test done on the bike in the next few weeks, and hopefully a valve check also. When the bike is apart I will also check the throttle bodies and the butterflies. Funny thing is I managed to get much better milage when using the gas in the US than I ever have in Canada. One day I actually got 51 miles to the first 8th of a tank of fuel. Go figure. I guess we have crappy gas here up north. I never once used any injector cleaned or any other additive while on the trip, where as my friends had to use some "StarTron" every fill up in their bikes, or they would run crappy. I guess I just need to ride it fast.lol
Mihalis fjr
Well-known member
Realy very odd all this..My bike is just the same model like yours..and from 2004 early when i bought her..i never had a like this problem...realy very odd....
steve'o'
Well-known member
Just wondering if the Barbarian mod would be a fix or just a bandaid?
Mihalis fjr
Well-known member
I don't think it..!It looks like something closed,sticking after the winter off period..I think you must try a good Yamaha workshop and let them check it..I am not sure but perhaps with very low possibilities the ECU don't doing a good fuel management to 4 cylinder,i don't know why..?!The black colour on the spark plug it saw a very rich mixture!Tell me again..this problem begins suddenly after a winter off period?or not?if your problem comming from electrics then and the other cylinder must doing the same problem..but it is not!
Mihalis fjr
Well-known member
I think you must first pull off the 4 throttle body,or if it is possible clean it without pull it off from the other throttle bodies clean it well and have a good look on and in it..on all the throttle bodies there is a air screw for the synchronitation TBS.probably you must pull this screw out and have a good look if this screw is broken or bend or something wrong there..after put it back in the same potition about(be carefull dont force it in the end..simple turn it slightly to the end and turn it back about 2 rounds..After this job you must do again a TBS!
Mihalis fjr
Well-known member
Adding the air screw of the 4 throttle body only..
Canadian FJR
Canadian FJR
"So I am back from Laconia, 3300 kms, and the bike worked, good"
Glad to hear you made it back and the bike worked okay. Keep us posted.
Canadian FJR
Glad to hear you made it back and the bike worked okay. Keep us posted.
Canadian FJR
You shouldn't be fouling plugs. I'd say if it made any difference it would be a band-aid.
Let's try to look at this logically. There are a whole lot of things that can't be causing the problem, like any of the FI system sensors because the ECU modifies all of the cylinders fueling the same amount based on their inputs and you are only having the problem in one cylinder. You've already ruled out the fuel injector since you swapped with an adjacent cylinder and the problem didn't move.
We still haven't determined if the problem is that the fueling is wrong and that is what is fouling the #4 plug, or if the ignition isn't firing right, and that is what's making them look fouled. Before I went to the considerable effort of ripping out the throttle bodies (they all come off together, BTW, and they are difficult to get to) I'd want to know that you were at least heading in the right direction. In other words, do some more diagnostic work first. You may want to bring it somewhere that has a scope to view the ignition and fuel injection signals.
