| Author | Message | ||
     Gcooperlll |
2008 XB12XT with 55000 miles. Engine dies (both cylinders) at approximately 3/4 throttle. Back off the throttle and engine fires. Idles, runs good to cutoff. Cuts out in all gears at same throttle position. Buelltooth TPS readings .3 to 3.95 v and it be smooth. At about 1.0 VDC on tps the engine dies. Have reset tps, swapped the ecm with my other 08 XT, new iridium plugs. Am at a loss and I need HELP!! Cooper | ||
| Griffmeister |
With that description kind of inclined to suggest mechanical interference with a critical wire. Either in the way that the cables flex, the bell crank on the throttle body or maybe even between the hand grip and kill switch wiring. Either that or need more clues. | ||
| Etennuly |
Could be a weak fuel pump or plugged filter. | ||
| Gcooperlll |
Fresh out of clues. Checked the cable routing and the tps voltage - running and not running - all good. will bypass kill switch in the am. when engine dies the injectors are still firing. I guess I'll just start the Easter Egg Hunt and start swapping components from the spare 08. | ||
| Gcooperlll |
Can't understand how a weak pump or plugged filter could shut down the engine at the same throttle position irrespective of load or gear. Bike runs fine up to 85mph in fifth as long as I don't use more than 3/4 throttle. Will put the pressure gauge on it tomorrow. | ||
| 651lance |
Does the engine recover if you roll the throttle back or does it just shut down completely? | ||
| Dave |
Replace TPS? The mechanical action of the throttle is being converted to vdc. If the sensor is bad, it makes sense to me that at throttle angle x°, vdc goes wonky. DAve | ||
| Etennuly |
I have had more than one vehicle through my shop with an electric pump and a water or dirt clogged fuel filter. They can flow a certain amount of fuel. When the blockage holds up fuel pressure at say 30 percent, the engine starts, idles fine, revving is not a problem, but under load,it literally runs out of gas. It will do it at the same point of throttle/load every time the engine needs to go beyond 31 percent or more to maintain its fuel air ratio. It can quit at the same point every time. Running out of enough gas is the same as shutting off the switch. Has it fouled plugs? If so these are likely not the problem. If it is doing all of this high speed cutting out with dry plugs, the fuel is somehow being cut off. There was also the wiring problem in the fuel pump area. Wires were run over a sharp casting edge in the tanks fuel pump mount. It would mess with the low fuel light and the intermittent pump running. Check the fuel tank vent also. Check ball fail or mud dobbers. | ||
| Gcooperlll |
When the engine dies ( like a light switch turning off - no burbles coughs or hiccups) I can roll back the throttle a wee bit and the engine will fire back up after about 6 seconds. will swap out the tps even though the mechanical conversion to Vdc appears to function correctly and smoothly. ran the bike on side stand with fuel cap open and it still shut off at 3/4 throttle. Bike has not fouled the new iridium plugs. Starts idles and revs as it should. Maybe let the boy ride it and use the issue as a valet feature. | ||
| Tootal |
Do you have ECM SPY or some other way to watch the ecm in real time? It would be interesting to check for any codes and watch the tps live. It would allow you to test the fuel pump etc. | ||
| Gcooperlll |
I do have Buelltooth - bike is not throwing any error codes. Watched tps live and all appears well other than engine turns off at about 1.0 vdc on tps - tps voltage continues to climb as I roll on more throttle. All diagnostic tests run with Buelltooth have passed muster. | ||
| Shoggin |
Have you messed with the airbox or air filter? If the rubber air horn piece isn't installed or seated properly in the base, it will do that (surprisingly). | ||
| Tootal |
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| Gcooperlll |
Tootal thanks for the pics but I have all the Uly manuals from 2006 thru 2009. Once again the bike does not throw any trouble codes and works with the Buelltooth. Shogin I did have the air box off to change plugs will double check the rubber air horn for correct installation. | ||
| Tootal |
My intention was to point at the ecm grounds. I had an issue years ago that ended up being a ground at a certain rpm. It was more the vibration at that point than the rpm itself. Just spit balling. | ||
| Gcooperlll |
Copy that Tootal First thing I did when I got the bike was to redo all the grounds. Do appreciate your attention to this issue. | ||
| Shoggin |
Yes, the base of the rubber airhorn sandwiches the top and bottom of the airbox baseplate. Good luck! | ||
| Ourdee |
Etennuly, There was also the wiring problem in the fuel pump area. Wires were run over a sharp casting edge in the tanks fuel pump mount. It would mess with the low fuel light and the intermittent pump running. My low fuel warning hasn't been kicking in. Are you insinuating that may have a chafed wire in the tank to worry about? | ||
| Etennuly |
It was a common issue in 06-7. Allegedly fixed for 08. But I fixed an 08 with the Chaffed wires. Probably not your issue because of how consistently it has the problem. Can cause low fuel light on or off, and fuel pump to cut out and other strange things can happen. But I never heard of one doing a consistent cut out exactly like yours. I'm trying to give you some ideas. I have had plugged fuel filters cause a pretty consistent cut out at a specific rpm. You could also check the cam sensor and it's wiring. | ||
| Smorris |
cold soldier joint for grounds at steering head always a problem point. BUT also the cold soldier joint for the power wires and the tan turn signal wires are buried in the loom where the loom AND the throttle cables come back to the frame from behind the fly screen. no codes thrown with breaks hidden deep in the red bundle but will give you dead and alive situation. 1 of my reds was broken wires inside the red insulation with no visible problem | ||
| Pushr0d |
I had the same issue! I had recently purchased a 2008 Uly, and upon getting it home, proceeded to right some of the several wrongs I found. That included wire management, as a PO had made a good mess. After the clean up, I had the same throttle problem as the OP. I tried all sorts of things, including replacement of the TPS, and I tried a friend's good ECU. No joy. Following a Buell Tech's advice, I went back into the wiring that I 'cleaned up' on the lower left side of the bike, including the CPS lead and connector. During the first go-round, I had lassoed all the R/R leads and the CPS wires and secured them against the left frame rail and the 'strut' that leads aft. So, I cut all the zipties, and looked carefully at how the wires and cables should be arranged. The R/R cable and the other two conductor cable were apparently misrouted, and a large loop of cable had been 'bundled' in the front. After taking the connectors apart, and cleaning and greasing the terminals, I re-routed them. The 'extra' cable I re-located at the rear of the engine. The CPS cable connector, as it turned out, was not mounted to the frame rail pin. I hadn't noticed the pin before. So, after taking the connector apart and cleaning a good amount of mung out of it, I re-routed the cable so the connector could mount properly, and the wire was up and out of the vicinity of the power cables. Riding the bike to work the next morning, I didn't notice any difference in performance, since I didn't want to kill the engine while in traffic. But, when I got to the last stretch of road to the office, I tried to wring the throttle to see where it failed. The bike never faltered! It revved right up and took off. I was right surprised - both that it didn't die, and I'd not experienced the engine flexing its muscle! So, it seems that the CPS circuit was the culprit. Either the crap in the connector was causing a weird signal that confused the ECU, or (more probably) the proximity of the CPS cable to the power cables when I zip-tied them together was generating interference in the CPS output to the ECU. Hope this helps! | ||
| Gcooperlll |
Turns out that was my issue also. The last owner had rewrapped the loom to the cross bar instead of the left air intake landing. In doing the reroute he laid an extra loop of the CPS cable inline with the voltage regulator cable. Once I rerouted the CPS cable to pass the VR cable at right angles all became good with the world. VR was probably inducing EMI to the CPS which gave the ECM a headache. Active lines crossing at 90 degrees with not induce EMI. Why this happened at a particular throttle position I haven't a clue nor do I care. Thanks to all for their help. vr Cooper | ||
| Tootal |
Wow, I never would have figured that one out! Well done gents! Note to self, don't touch the friggen wiring!! | ||
| Etennuly |
Learning here never stops. | ||
| Pushr0d |
GcooperIII, that's exactly what caused my problem! The harness was ziptied (with at least a half-dozen ties!) to the front frame spar and all the way along the horizontal strut above the primary. I didn't realize the OEM arrangement has fir cone zipties under the cooling air intake fairing. I hadn't noticed the holes when I had it off. I've got a bag of the proper fasteners on their way! Now, to fix the buggered-up wiring under the flyscreen! |
