So I've just done the valve clearances and to my surprise, most were out of spec. All back together but still have the same symptoms. 


I bought a new pattern coil stick, to swap out and test each cylinder, because when the revs do creep down you hear a missing. But made no difference.

Will the idle not drop if you adjust the idle adjuster?

- No the idle won't change/drop

Did you reset the ECU? It is a learning ECU.

- No I haven't, I didn't know you could. I've cleared any memory faults. How do I reset the ECU?

Did you check the fuel line pressure? Should be 47PsiWhen you tested the items did you check the wiring connection back to the ECU? Did you check the Multi point earth which is prone to corrosion?Was the fast idle included with the replacement throttle bodies, is it adjusted properly and is a common source of high idle issues.
Has the TPS been set correctly?Did you try disconecting the O2 sensor?

- Yes Fuel pressure is spot on. I only swapped it out because I was starting to not trust my pressure tester. (At least I know my gauge is good  )


- Yeah Earth is decent, cleaned it anyway.


- Yes the fast idle was included. The throttle bodies I purchased were complete as if you just took the throttle cables off. With the new (Used) throttle bodies I'm having the same high idle issues, so I would think they are both factory set.


- TPS has been set within spec.

The symptoms are suggesting issues with the cold start circuit.  There are several sensor the ECU uses to control that circuit.  You state you've tested them, try disconnecting the temperature sensors one at a time see if you can get the revs to drop to 1200. Test fuel pump pressure, you'll need a gauge for that. Also check the fuel return circuit ie blocked or restricted.  Check the air box for restrictions or damage eg holes/splits. Look for signs of a boost plug these are plugged into air temperature sensor in the intake, these fail overtime.  Some are home made bodge jobs and cut into the loom, only to be removed on selling.  The std sensor will test ok, but if the loom is damage the circuit won't work correctly.  Check the loom for signs of an alarm having been removed or fitted incorrectly.


From what you've stated, over fueling is your issue, but the problem may well not sit n the fueling circuit.  But rather one of the supporting circuits. 

- Air Temp Sensor is standard but I will check for any dodging wiring.


- Coolant Temp Sensor is working has the readout on the dash is correct. But I will pull plugs to see if I can get it to act differently.


- No signs of an alarm being fitted.


Thanks for sticking with me guys. I think I'm going to have to start checking pins at the ECU which I'm not looking forward too...


I have an had an issue before with a different bike I owned, where the crank sensor would fail when hot. But it would start missing on all cylinders, acting like a kangaroo.
I'm just starting to wonder if it's starting to die on my FZ8. I can sort of keep the bike running if I keep the revs above 3K so it doesn't make sense the CPS not working at low revs does it??


I'll update again, when I've done the next round of tests/swapping out.

Hi guys!
 
Looking for some input on an issue I have with my 2012 Yamaha Fazer 800 14,00 miles. I bought it with the issue I’m trying to fix. I have no history on the bike, the dealer I bought it from couldn’t fix it.
 
Check out the video of my issue - http://youtu.be/50X8uXyvpzE?si=qrf3s8njx5ULxREP
 
Originally the fuel pump would be working all the time when you key on, then while running it would have inconsistent revs as shown. With the fuel pump relay not switching off, I fixed this buy getting a used ECU. I thought perhaps it would fix both issues but it didn’t. (I haven’t yet flashed this ECU to my lockset, I’m using an emulator until I can actually get the bike running correctly)
 
I have no fault codes on the dash, and I have tested the following.

• Intake Air Pressure Sensor
• Air Temp Sensor
• Cam sensor
• Crank Sensor
• TPS
• Secondary TPS
• All 4 coils
• Atmospheric pressure Sensor
• Fuel pump pressure (Sits a 3.0 bar while the issue is happening)
• Fuel pressure regulator (Changed it just to be sure)
• Engine Temp Sensor (As shown the revs do come down as the bike gets hotter)
• Balanced the throttle bodies (Spot on, no need to adjust)

All parts are within spec or either operate to the genuine manual.
Diag tests on the speedo all show and work correctly.
The spark plugs are sooty, so it looks like it’s over fuelling. The bike as far as I know is completely standard. Has standard exhaust, air filter and as both ECUs are showing the same symptoms, I doubt they have been both mapped.
 
But as the video shows the tacho jumping everywhere, it does feel like it’s missing, pointing to an electrical fault. But with all plugs being sooty, I can see a plug/coil braking down.
I have already checked multiple forums for a fault like this but had no luck.
 
Is this an issue with Fazers you seen before?
 
Any input would be greatly appreciated, maybe I’m being a fool and missing something obvious here!