FZ1 revs hanging, engine appears to be running rich

R

regder

Well-known member
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This has been an issue since the summer that I can't seem to figure out how to fix. Engine rpm's seem to hang at about 5-6k and take a long time to come down.

The bike

'07 FZ1, full Yoshimura exhaust, BMC air filter, cut air box, Ivan's smaller sub throttle plates, PC3 and Ignition Module, 02 eliminator, now removed Ivan's Fuel Cut Eliminator

Original malfunction

- Sub throttle motor failed, and about the same time the FCE started acting up. Dug in and replaced the sub throttle motor which involved removing and reinstalling the throttle bodies. Found FCE had a broken connection on one of the wires leading to the atmospheric pressure sensor, removed it altogether. Reinstalled throttle bodies. Immediately noticed rpm hang and popping/backfiring from the exhaust. Engine when cold will backfire, throwing flames from exhaust.

What has been done trying to figure it out

- Confirmed throttle cable not binding
- Replaced Thermowax unit that controls cold idle
- Atmospheric and intake air pressure readings match up
- Re and re throttle bodies again
- Synced throttle bodies
- Swapped TPS from another bike
- Removed 02 eliminator and plugged 02 back in
- Disconnected Dynojet Ignition Module
- Tried unplugging PC3, and changing map. The issue seems to be better without the PC3, not good, but better. Without PC3, there is a huge amount of popping from exhaust. PC3 is currently reconnected
- Replaced spark plugs and installed coils from other bike
- Checked for vacuum leaks
- Disconnected battery for ten minutes and reconnected

Issue is unchanged across all those steps except for the PC3

Vid of issue
https://vid.me/czpf

Backfire
https://vid.me/borM

Without PC3
https://vid.me/a82o

With PC3
https://vid.me/Gb5J

Any ideas?
 
Last edited:
Looks like the bike is running really lean (i.e. flames).

And re: your rev hang problem. Without knowing what the cause is you can fix it if you get the ECU flashed to disable "injector cut on deceleration" then you can then control the rev hanging with the Power Commander. With the ecu in stock form fuel you add to the 0% column is ignored over most of the RPM range.

Plug your laptop into the power commander, fire up the software and enable "tracer". Then re-do your rev hang video while recording the screen of the laptop. Would be interested to see if the power commander thinks the throttle is hanging or not.
 
With all those mods definetely a fuelling issue but with so many different mods it will be hard to trace.
 
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