| Author | Message | ||
     Buell_41 |
... But isn't. Some of you may remember me having bike problems and replacing the fuel pump. The original thread has probably been archived. Anyway, that wasn't the problem and I've gone on to test and replace the coil... Still no resolution... So it misses or does something that feels like a miss. Any ideas? | ||
| Generationx1 |
sometimes my XB will miss if the gas is old or low octane/from an iffy gas station. I have ran Lucas fuel treatment through the system and it ran better. Make sure the plugs and wires are snug..the bike as you know kicks out allot of vibration. | ||
| Rocketsprink |
really loose primary chain? would make the bike feel jerky. Just a shot in the dark | ||
| Iamarchangel |
Can you give us a bit more info on what the miss is like? When does it happen? What rpm? How long does it last? In turns, on straights? I remember thinking on the original thread that it sounded like your intake air temperature sensor needed replacing. | ||
| Buell_41 |
it feels like a power loss followed by a big kick in the butt. Imagine stop and go traffic only its in milliseconds. Its the worst at 30-35mph in 2nd. However, it will do it to some extent or another under any condition that isn't hard accel. It even does it when I'm stuck behind a cager who is slowly accelerating away from a stoplight. Its better when its cold. But idle is erratic (surges) at any ambient temp. Between surges, indicated rpm is just over 1k. It surges in cycles of about 10sec. (and its very consistent like pressure is being relieved over and over). Pluges, wires, coil, chain and the teeth on the output sprocket for the primary chain all look or have physically tested and check out. I've done the propane test on the intake seals immediately after getting home from work... didn't even shut the thing off. No change in RPM...................... | ||
| Jos51700 |
What is AFV? | ||
| Jos51700 |
After reviewing your original thread: I would STILL check fuel pressure (Shotgunning parts? No thanks, diagnose if possible.) It could also be a broken wire in the harness. It seems like XBS models like to rub though on the bracing under the seat. Usually, this is a code-tossing, run-one-minute-dead-the-next issue, though. Also, if you have ECMspy or VDSTS, look at throttle position sensor readings as you open/close throttle. It should be smooth, with no jumps or breaks. Does it do it in EVERY gear? Does it happen at ANY speed? What about a given speed regardless of gear position? It is entirely possible, given the Poo that was in your old filter sock, that the fuel injectors have gunked up screens. If the AFV is still high, I would check fuel pressure first (Actual pressure, not "is it running?"), than I would probably look at the injector screens. AFV is your next logical step. Remember, AFV will climb a little naturally with cooler weather...but where is it now? Try unplugging the fuel tank vent hose under the airbox cover and going for a long-ish ride. Any mods to the bike? Muffler? Airbox? Turbo? | ||
| Buell_41 |
TPS is smooth and calibrated. Does it do it in EVERY gear? Yes, when no load. Does it happen at ANY speed? All speeds that aren't idle. What about a given speed regardless of gear position? Yes, in fact putting it in 4th at 30mph makes it extra bad... head literally snaps back and forth. AFV is 117 at idle and climbs up to 127 when revving with bike on the kickstand. No turbo. Stock airbox. Re-routed vent lines to just behind the fan and terminated with a micro "bullet" filter. | ||
| Iamarchangel |
In some other thread, somebody talked about a wiring problem that was under that seat. What made it especially frustrating was that when nobody was on the seat, there was no problem. It was only when somebody was actually sitting on the seat that the wires were in the wrong position. So, tests were fine, riding was bad. Anybody else remember more about that? | ||
| Gschuette |
Check your battery connections. Mine did that when one of them loosened up. | ||
| Turk |
With AFVs that high I'd suggest looking for intake leaks. | ||
| Petebueller |
You could try the head temp sensor or O2 sensor. The temp sensor wire is draped over the head and wiggles because of the rubber mounting. You could strap the sensor wires gently up to the frame and see if that makes a difference. | ||
| Moosestang |
What is this bullet filter you speak of? Does it have a breather on it? Have you checked the static timing? So is the bike surging or missing? i'm confused. | ||
| Jos51700 |
One thing I've seen before, but not often, and is COMPLETELY irrelevant if you've CHANGED plugs trying to figure this out: Sometimes the center-electrode insulator can break loose, but not break up. It then slides down the center electrode when the plug is installed and shrouds the spark. It is free to slide up and down and will blow up out of the way under certain conditions, and so provides an intermittent misfire . Then, when you remove and inspect the offending spark plug, you (naturally) turn it over, and the electrode insulator slides back down inside the plug, and everything looks good! VERY frustrating to find if you don't replace spark plugs... | ||
| Jlnance |
If it happens as you sit at 55 mph in 5th gear, it's the fuel injection system adjusting itself. | ||
| Ourdee |
I don't run in 4th gear at anything under 40 mph. Does it smooth out at higher rpms like over 55 in 5th? Just my thought. | ||
| Buell_41 |
I believe to have found the problem!!!!! O2 sensor looks to have gone bad. The manual says the voltage off the sensor should be between .41V and .56V. I downloaded ECMspy and started looking and the numbers. At operating temp. the indicated voltage was 0.03V (no thats not a mistype). The reason I didn't find it is because it was .49V at startup (and when cold which is where I would have used a meter). It was only after the warmup did the value go down that far. As a cross check, I unplugged the O2 sensor and watched the voltage.... this time it stayed right at .49V. So I pose this question to you all. Yesterday, I rode around with the sensor disconnected and I forced an AFV of 100% (remember the bike had a learned value of 115). Even with both values correct, got the missing symptom. With the sensor disconneted the bike NEVER goes into closed loop mode. So assuming all the numbers were correct, why did I still get the missing? | ||
| Buell_41 |
I'll get a replacement, ride the pee out of it and report back. | ||
| M1combat |
intake leak. | ||
| Buell_41 |
did propane test. no change in rpm. | ||
| Jos51700 |
If the symptom did not change at all, the O2 sensor is not it. If it was "different" with a forced AFV, then my guess is the AFV needs to adapt to some other value to get fuel in the right zone, but you're on the right track. Remember, the O2 sensor output is an average of values, not a constant output, but at .03, I'd say get a new one. | ||
| Sharkytattoo |
Does it seem to surge around 2500-3500rpm at cruising speed? Seems fine if you power thru that rpm range? Only happens at steady throttle? If so, replace your TPS. | ||
| Sparky |
The O2 sensor only has one wire, thus depends on a good ground connection through the exhaust pipe to the engine ground point for maintaining a proper signal. Suppose the exhaust pipe is loose or otherwise has poor ground conductivity to the head. I would think that could cause anomalous O2 sensor voltage readings. Do you suppose this could be checked out by clipping an external ground cable, say, a battery jumper cable, to the outside of the O2 sensor and the other end to a good engine ground? | ||
| Jos51700 |
The O2 sensor DOES NOT REQUIRE GROUND. It produces voltage that the ECM monitors, and therefore ground is irrelevant (on a one-wire O2 sensor, anyways). On most sensors, the ECM produces a 5 volt "reference" signal that the sensor modifies in some way, and the ECM monitors that change to interpret the signal, the O2 is the exception. | ||
| Sparky |
It sure does need a ground. It produces a voltage potential with respect to the body of the sensor which is screwed into the exhaust pipe, yes/no? Words from the Firebolt FSM,
I take that to mean improperly grounded. But more to the point, the poster's problem appears to be some kind of a load or short circuit between the sensor and ECM because as the engine warms up, the voltage goes down to practically nothing. And, if I understood correctly what was said a couple posts above, when read at the unplugged sensor, it reads full value, 4.9V. If the sensor were bad though, wouldn't it read low unplugged, thus verifying what ECMspy indicated? Maybe the O2 sensor is defective and is putting out too weak of a voltage that gets loaded down while plugged into the ECM? | ||
| Jos51700 |
The service manual is referring to the possibility of a loose O2 sensor resulting in an airleak through the threads, which makes AFV go sky-high. Think: the sensor produces from zero to one volt. There's only one wire. Where's the voltage go? If it goes to ground through the sensor body, what's the wire for? The ECM does follow O2 sensor voltage in reference to ground (that's voltage by definition: a difference in potential between two places, hot and ground), but the ground is in the ECM. That's why there's no dedicated ground wire on a header that has dirt and soot (albeit, lots of nice, conductive carbon) and no solid mechanical connection everywhere it meets a well-grounded componant. BTW, .49 volts is approximately half of the sensors possible output, and also about what the ECM considers "ideal/stoichiometric". If the O2 sensor output is off from this, even if the bike was spot-on, then the ECM would make the bike go "out" from ideal...It can and will cause the bike to "chase it's tail" if the the O2 sensor fails in the right way. | ||
| Sparky |
If the O2 sensor is bad, it can be removed and tested as follows per the last paragraph on this page: Testing O2 sensors on the workbench. Note the author says, "Clamp your negative voltmeter lead to the case, and the positive to the output wire." That statement validates what I said about the sensor body being the ground for the device. True, if the sensor is loose, it may not only leak air but it may also cause low or erratic O2 voltage signals to the ECM because high resistance at the sensor/exhaust pipe interface prevents the sensor from delivering its normal voltage. | ||
| Brumbear |
leave it at the mall with the key in the ign and problem solved. But why don't you try chaning a coil and plugs and wires | ||
| Iamarchangel |
But why don't you try chaning a coil and plugs and wires The thing about that approach is, if you're just going to throw parts at it, it would be cheaper and less stressful to buy a new bike. The real answer is that nothing here indicates those parts have to be changed. It sparks, it runs, it gets warm and then goes to poo. Typically those components are not problems if the bike is warm and running. Of course, if it's cold and/or wet and there's problems, those are the usual suspects. Did you have a specific reason in mind? | ||
| Bombardier |
O2 does need a ground. Replaced the standard O2 with a narrow band four wire. 1 earth wire, 1 sensor wire, 1 positive for the heater and, 1 negative for the heater. Original startup voltage took up to 3 minutes - now 20-30 seconds - no fouled plugs. This sounds like a case of the chicken and the egg - which comes first? The O2 sensors are not that expensive and not too hard to replace. For my money I would replace the standard item if it has gone out of spec. The four wire setup is quite easy as the sensor fits the same as a standard one, the earth for the sensor and the heater both go to the negative on the battery and the positive for the heater clips into the tail light power supply so when ignition is on so is the heater. I changed both the O2 and the ETS at the same time and thought I was on the wrong bike. A smooth as a Japper and nearly as boring. How are the plugs looking for colour? If the bike is running lean they will be a whitish if not white colour. |
