I have a misfire when I pull away at small throttle positions. Changed plugs, air filters, fuel relay, PC3 has been dyno tuned, TPS reset, all codes reset. Mech now says there is an earth fault and he can only get the bike to run through his dyno. He says he has tried another ECU, no different. He is now saying the loom is shot. It all sounds like bullshite to me so I need some help from you guys.
The battery 'looks' OK and the bike did start fine, I hadn't needed to test the battery. I had already fitted an additional earth lead between the battery neg and an engine bolt.
I've found a poorly battery contributes to poor running, especially at the lower rev range. for having a secondary earth lead
Yeah that's what I thought too but the mech says it is a bad earth, ecu fault, bad loom, injector gone rogue. Not had the bike very long and it is now very clear that the PO had some pretty dodgy servicing done. The air filters had rusted and collapsed inside the tubes despite coming with recent service history!!
I'll throw my hat in the ring. Having discussed earthing with my trusted mechanic, he told me the 749/999 wiring looms have a history of dodgy earths. One problem is that the earths come together in the loom and the joints can corrode. Unfortunately, there is no good way of checking it without stripping it out. Generally running a secondary earth helps, but if the loom is too badly butchered then you're snookered. One thing to check is that there is a black flying lead which attaches from the main loom to one of the ECU's mounting bolts. It's a PITA to get to, but if it is not connected or damaged it may point to some of the weirdness. Also see if engine check lamp lit on the clocks, if so you can read out the fault codes which may give you an idea where to look.
OK so this is an email I received today from the garage. It went in to the shop with a low rev 10% throttle misfire. Pulling away it would misfire, felt like over fuelling to me. Here is the email. have tried to call you on more than one occasion without success, Sorry but if i was to take every call that came through to the office I would not get anything done in the day, so I will always let you know what is happening when i have something to give you. As discussed late last week I removed the battery and associated ECU fittings and was shocked and horrified to find the condition of the electrical system to be in a very poor state of cleanliness and fit up, with wires chrushed and protective coverings missing or falling off. Also as you were aware we removed the airbox top and air tubes to find these to be filthy and the filters to be breaking up. So to date to sum up; Removed airbox and airtubes cleaned out. Replace airfilters Replace injectors NO CHANGE WITH MISFIRE BUT MUCH SHARPER ENGINE NOW Replace ignition coils and test NO CHANGE MISFIRE STILL THERE (remove ignition coils and refit originals) Remove battery and ecu assembly Carry out wire repairs Run ECU check’s clearing faults which were logged Refit assembly and test, further faults found. Fan comes on and fuel pump primes continually Check wiring again and make further adjustments and checks Immobiliser now not recognised Replace ECU with used item to check system NO MORE FUNNY THINGS GOING ON SUCH AS FAN COMING ON AND INJECTION SYSTEM WORKING CORRECTLY BUT NO SPARK DUE TO ECU BEING PRE PROGRAMED. Send ECU off to have immobiliser removed Awaiting return of this replacement ECU. As of yesterday the ECU has not been returned yet. Hope this helps
The fan/pump fault is indicative of a polarity inversion damaging the ECU. The cynic in me thinks they either inverted some jump leads on the battery after flattening it or they inverted the fly leads on their diagnostic lead. There is a work around by running the middle wire of the diagnostic plug to earth.
That would explain a lot. My bike has been there for almost 3 weeks now with little progress. During the first week they tested the ecu for faults and then after this was when the excuses started. The mech even went as far to say to me 'he wished he had never started the job'. Why would you say that unless something had gone wrong. I will put your info to him and see what they say. cheers mate.
