RossKean
Well-known member
The two pressure sensors are the same part number. I wonder what happens if they are swapped??
Is one more important than the other?
Is one more important than the other?
Engine only runs with vacuum line disconnected
- Thread starter Zpetrus
- Start date
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torch
Well-known member
I went out and unplugged the AP sensor on my 03. The value jumped to 924, and set error code 23. I exited Diag and started the bike. It started, but ran like crap, popping, spitting, etc. and set the Check Engine light. I plugged the sensor back in with the engine running and after about 2 seconds, it smoothed right out and the CE light went out. The code remained stored in 61 until cleared by toggling the kill switch in 62.
I find it very strange that yours only climbed to 120 with the sensor disconnected. I wonder if there is an issue with either the wiring or (God forbid) the ECU itself.
I find it very strange that yours only climbed to 120 with the sensor disconnected. I wonder if there is an issue with either the wiring or (God forbid) the ECU itself.
Curiouser and curiouser said Z. Torch, mine threw the same code when I disconnected the AP sensor. But today I took a ride over to a friend who has a perfectly running '04 and who's son is a motorcycle mechanic. He let me run the diag on his bike so I can see that values on a good running bike.
(he did not even know such a thing existed)
TPS his 16-99 mine 16-100
AP his 92 mine (different day) 97
Throttle pressure sensor his 0-5 Mine 0-7
????? His runs with all the vacuum lines connected though.
(he did not even know such a thing existed)
TPS his 16-99 mine 16-100
AP his 92 mine (different day) 97
Throttle pressure sensor his 0-5 Mine 0-7
????? His runs with all the vacuum lines connected though.
torch
Well-known member
Throttle pressure sensor??? Intake air pressure sensor maybe?
Interesting difference in AP value between my 03 and his 04. Maybe Yamaha re-wrote some code so things are reported differently in 04. Did you D/C the sensor and see what happens to the value by any chance?
Let us assume that your sensors are working properly, based on that comparison. Odd that it's throwing those codes though. Any chance your buddy would let you put your ECU in his bike, just to verify that it's not the ECU itself causing havoc?
If in fact the sensors work reliably and the ECU is good and there is no intermittent faults in the wiring, then the logical conclusion is that the sensors are reporting symptoms of a mechanical fault. So back to the basics: fuel, spark, compression, timing.
An unlit propane torch can help diagnose fuel issues. If it runs better when inserted into the intake, that suggests things are lean. It can also be used to locate vacuum leaks by moving the torch tip around the boots and throttle bodies -- if there's a leak, it will suck in propane and the idle will change speed and/or quality.
The fact that your bike does draw vacuum when cranking over suggests there's no significant vacuum leaks and that there is at least some compression. But it wouldn't hurt to do a compression test just to verify. I would also have a look at those new plugs. It's possible that they got fouled during all the fiddling, and require replacement again.
It might be helpful to throw a set of carb sticks on to check actual vacuum during cranking/running. Low vacuum could be a symptom of a timing chain issue -- possibly jumped a tooth? Easy enough to check, but requires removing the cam cover and the right side crank cover to see if all the dots line up properly.
Interesting difference in AP value between my 03 and his 04. Maybe Yamaha re-wrote some code so things are reported differently in 04. Did you D/C the sensor and see what happens to the value by any chance?
Let us assume that your sensors are working properly, based on that comparison. Odd that it's throwing those codes though. Any chance your buddy would let you put your ECU in his bike, just to verify that it's not the ECU itself causing havoc?
If in fact the sensors work reliably and the ECU is good and there is no intermittent faults in the wiring, then the logical conclusion is that the sensors are reporting symptoms of a mechanical fault. So back to the basics: fuel, spark, compression, timing.
An unlit propane torch can help diagnose fuel issues. If it runs better when inserted into the intake, that suggests things are lean. It can also be used to locate vacuum leaks by moving the torch tip around the boots and throttle bodies -- if there's a leak, it will suck in propane and the idle will change speed and/or quality.
The fact that your bike does draw vacuum when cranking over suggests there's no significant vacuum leaks and that there is at least some compression. But it wouldn't hurt to do a compression test just to verify. I would also have a look at those new plugs. It's possible that they got fouled during all the fiddling, and require replacement again.
It might be helpful to throw a set of carb sticks on to check actual vacuum during cranking/running. Low vacuum could be a symptom of a timing chain issue -- possibly jumped a tooth? Easy enough to check, but requires removing the cam cover and the right side crank cover to see if all the dots line up properly.
road runner
Well-known member
Yes basics. Spark, fuel, air. Check the compression, throw new plugs in it, and check spark on all 4. If still not right check fuel pressure. It looks like the MAP and temp sensors are working so it may be fuel issue.
I ordered a new throttle pressure sensor and fuel regulator. The TPS was before I ran diagnostics on my friend's bike and realized the Specs in the shop manual must be wrong. I am doubtful of the compression and timing issues due to the low milage and the fact that it runs fairly well with the vacuum line disconnected from the fuel regulator. We will see and I will keep you all posted. Again thanks for all your insight and suggestions.
RossKean
Well-known member
Waiting with baited breath!
Pretty sure it is going to be one of those "D'oh" moments once you find the smoking gun.
torch
Well-known member
Yes, very low mileage. Highly unlikely that compression is off due to cylinder wear. But, hasn't run for 16 years. It is entirely possible that the rings or automatic cam chain adjuster are stuck from sitting. You asked for diagnostic steps instead of throwing parts and money at it. Compression and vacuum tests are cheap and easy (especially if you have or can borrow the tools from your buddy's son, the bike mechanic).
Since the electronic diagnostic steps (which are the cheapest and easiest things to try first) haven't revealed the smoking gun, I would move to the next level before reverting to throwing parts at it. Just my 2¢.
RossKean
Well-known member
Do you think there is any chance that the CCT got stuck and the chain jumped a tooth (or two)? I guess it might explain difficult start and crappy idle but maybe not the running better with the vacuum line disconnected? I wonder if it is worth taking the time to check that out before going further...
(I would replace the CCT with the updated version while I was at it.)
road runner
Well-known member
TPS is Throttle Position Sensor. IAPS is Intake Air Pressure Sensor. Which one did you order? I think you meant to order the IAPS. If a sensor or any electrical part is used, you can't return it. I would try the Fuel Pressure regulator first. If that fixes it, then you can return the IAPS. I say that because it appears that the IAPS is working as designed.
torch
Well-known member
I don't think it's likely, but I do think it's possible. Cheap and relatively easy to check.
road runner
Well-known member
Any news yet?
Well folks, I finally got to go back to the FJR project. Again Thanks for all the help. It is running like a top now. I wish I never saw the check engine light because it sent me down a rabbit hole I had no business in. As it turns out the new fuel pump had an o-ring that was not seated correctly. This kept the pump from building pressure at the fuel rail. I rigged a tester for fuel pump pressure and found it lacking (before I sent out for a pressuer regulator). I took the pump out again and reseated the o-ring and now it runs like a top. No Check Engine lights.
RossKean
Well-known member
Great news.
Normally, I would suggest going back to the last thing that was messed with but you did a bunch of stuff right off the bat. These bikes are exceptionally reliable and it is generally a matter of identifying a (relatively simple) root cause.
THANK YOU FOR GETTING BACK TO US. With many of these threads, the OP either gives up or fixes it and moves on without ever getting back to us about the root cause.
Now get out and put some miles on it!
Normally, I would suggest going back to the last thing that was messed with but you did a bunch of stuff right off the bat. These bikes are exceptionally reliable and it is generally a matter of identifying a (relatively simple) root cause.
THANK YOU FOR GETTING BACK TO US. With many of these threads, the OP either gives up or fixes it and moves on without ever getting back to us about the root cause.
Now get out and put some miles on it!
torch
Well-known member
Yes, thanks for the update!
road runner
Well-known member
Thanks for getting back to us. What you found totally makes sense. great job.
Appreciate the follow-up. This is how I learn new stuff.
