Surging at 3-4k RPM

[Flyingwombat]

So went on Reddit and was given a list:

- Relays
- Ignition coils
- Crank position sensor

[London_Phil]

Honestly cant se any of those...well maybe fuel pressure, but the cps generally will cause it to cut out, and coils will run rough rather than surge imho.

[the slow heart]

We have problems ... and this is not going to change,
then lets acknowledge the progress, to keep the faith -
well done compression testing, no mechanically caused leaks at number two.

ECU and coils are quite tricky to diagnose in home environment,
but you could swap items guessing. Can you get other ECU module, proven as operational?
Same for the ignition coils, you need friend with our bike model.
Would join the fighting alliance, but I am damn too eastward, mate 

[the slow heart]

Honestly cant se any of those...well maybe fuel pressure, but the cps generally will cause it to cut out, and coils will run rough rather than surge imho.

You are probably right, but since no better idea is coming, we have to just check the boxes remaining.
Vacuum leak may interfere with the pressure sensor/ IACV to cause surging,
but backfire has to be ignition/ timing related.

[Flyingwombat]

Hopefully the last post in this saga.

I went through the injectors again, cleaned them all up, replaced the one that had been misfiring (again). Rebalanced the throttle bodies.

Then ran the engine, still a little rough but the backfiring into the throttle bodies appeared fixed.

I plugged in the airbox sensors and it ran fine. At this point I dropped the airbox and it pulled the temperature sensor wires out of the connector. This was in August.

After that I had to to find a wiring loom with the same plugs to splice, but also had to do loads of DIY in preparation for the birth of my first child.

FINALLY got back to it! Spliced the plug on, double checked I hadn't missed anything and reassembled. Will take it for a spin soon but looking good so far.

[London_Phil]

Main thing is your making progress. Congrats on the new arrival, btw..