03 xb9 missfire at full throttle

[apsolus]

I've put over 4000 miles and 4 track days without changing anything. I bought the bike with that ecm in it. It is the for race use only Ecm. Ecmspy shows it as Buecb and that for an 03 Xb. Unless the ecm is now internally damaged how is it the problem? Let me go retest real quick hold on....

 

[apsolus]

my low fuel light came on so I decided best go get some premium and do more test riding. after a normal ride to the gas station I filled her up and hit the access road. I nailed it and bike fell on its face right around 4 thou and from then on would spit and sputter to about 5.5k then most notably if I keep the throttle wot the engine would loose all power and start to lose speed and rpm and wouldn't stop. so I get it home install ecmspy and wot in my garage in neutral. at wot rpm wont climb past 3thou or 2thou depending but as soon as I let off the bike falls into a lovely idle like nothings wrong. and yes the "21" code stil comes back with no other codes. at wot my o2 sensor shows .50 v
I did notice my fuel pulse width drops down a lot at wot

 

[Chicknstripn]

From what you just described it sounds like your fuel filter is clogged. Sounds like something is restricting fuel flow at high rpms.
I'd pull the fuel pump and give it a little TLC. A new filter and screen then see how she runs.
If you haven't done that yet. If you have sorry for not rereading the first page of this thread.
Then I'd move on to investigating the fuel injectors.

 

[apsolus]

u think full throttle at neutral would over load the fuel system? I did check the fuel pressure and it read 50 psi and the needle was just a bit shaky. as stated in the factory manual I revved the engine to 3thou and checked fuel pressure still at 50 psi. while riding and getting the bike to act up im just not convinced its a fuel pressure issue. I can get the bike to run fairly well after letting off the wot and cruising and id think if it were low fuel pressure I would slowly have performance improve rather than the bike suddently running great. while the bikes at wot bouncing off either 2k or 3k in the garage as soon as I let off she settles into a perfect idle.

I did find my front spark plug wire had rubbed on the idle cable. cable came apart at the coil and from the looks of it I could have been loosing spark as it jumped to the cable and to ground. ill retest tomorrow after putting it back together.

 

[thrstrmech]

I did find my front spark plug wire had rubbed on the idle cable

great find, but you also need to address the ecm and have it programmed properly or you may see other issues come up sooner or later.

 

[apsolus]

after I get it back together ill let everyone know what I find. so is chaffing in this area normal? my xb firebolt used to be a lightning fyi and when I first got the bike I noticed the front spark plug wire was rubbing on the throttle cables. after getting new wires I couldn't install the front one without it rubbing on the throttle cable. guess I ended up seeing no other way and just put it back together and here I am a few months later..

so ur convinced I have some programming issue and not just some race ecm with unused this and that causing the phantom 21 code. it doesn't even read when I do the code check manually. anyway let me go see about repairing the spark plug wire and putting this thing back together!! I want just one more good track day before I replace base gaskets.

 

[thrstrmech]

so ur convinced I have some programming issue and not just some race ecm with unused this and that causing the phantom 21 code.

yes, I have a race ecm on my bike too...regardless of it being a stock or race ecm for the '03 model...it should not be looking for an AMC since it wasn't in the design for that year model. it's kinda like this, ecm is looking for feed back from all the systems, may be a specified time coded for the system feedback. if the reply isn't returned in the time frame coded, it will simply fault it.

your ecm needs to be programmed for the current set up on your bike, if it isn't then you're gonna run into problems. this is why I harp on finding root cause of the problem(s) instead of band aid fixes. folks need to get out of the mind set of I want this fixed like yesterday and have patients. step back and trace out the changes done to the bike. what has changed, how was it changed...wire routing, wire protection, is it bent beyond it's maximum radius to not induce problems, proper and clean connections. added loads to the system power out put, are you exceeding it. these questions and more have to be addressed anytime changes are made to anything...this is in the planning stages or should be the first thing considered before jumping into any modification to any platform to include cause and affect.

you're on the right track on finding and repairing issues, [up] however, follow through...what's causing the code 21 knowing that the '03 model does not have an AMC, ecm programming? after all it's the heart of the bike...just saying

 

[apsolus]

as you can tell, I don't want you to be right but its looking that way. after repairing the worn line with some contact cement and installing the bad one on the rear where there is a lot more clearance and installed the new idle cable I had high hopes. like usual bike started right up like a champ and idled strong. after warm up I took off with great power. after getting it out on the road and opening up the throttle it died just like usual. this was a test ride and a parts run. im looking for the t27 shoulder bolts used all over this bike. so I proceeded with my ride and came home. are these ecm's expensive? just order from American sportbike? can I find those bolts online?

as far as anything done to the bike lately. I did replace the forks but nothing I can think of that could have led to this. one of the main reasons I don't want to install a new ecm is what if this ecmspy is showing me something that isn't there? you know? can the ecm be programmed using ecm spy?

 

[apsolus]

I did do swing arm bearing too.

 

[apsolus]

rotated my engine to replace base gaskets last night, pretty easy stuff and you don't even need to drain the oil. anyway I'm still looking for advice as far as how to get my hands on a new ecm for my bike. how bout a new cylinder head temp sensor? they don't make them or what?

 

[apsolus]

bike is back together and running perfect. I rotated the engine and replaced all the top end gaskets with a nice cheap buell set. came with updated metal base gaskets too. replaced piston rings and honed cylinders. installed new tps, o2, and cylinder head temp sensors and put it back together. bikes running better than ever. and yes the 21 code is still there. I think chkinstrip mentioned the prob could be the temp sensor on page one didn't he? I noticed the rear cylinder go really hot and that's why the whole thing was starting to seep oil as well. def feel like the right side scoop is a good adition here. and the header was white inside on the rear cylinder too! the new o2 sensor probably helped too. thanks for everyones help