Ive had a problem with one of my Fords while on LPG with a sprint gas system, at 3900 to 4300 Rpm there would be massive surging, once over that there was a considerable power loss, just like petrol fuel starvation.
I tried a new O2 sensor which solved this issue a year ago, this time after a full service/tune, new plugs, new coils, throttle body clean, Air filter clean, ECU reset, mixtures set and test leaner and richer, all Gas solenoids tested, new gas fuel filter, power valve stepper motor tested, all gas valves dismantled and tested the problem persisted.
What i managed to find out after days of google that no one wants to share is how to reset and recalibrate the LPG gas ECU.
Might save someone going to a LPG fitter to be told they need a new converter, i was just about to strip and rebuild the converter with a kit as it was the last piece of the puzzle before i found out how to do this.
For vehicles with a AEB295 LPG computer and similar AEB units.....
1. Warm up engine on petrol and turn off engine while still on petrol.
2. Disconnect LPG power connections from the battery terminals for 5-10 minutes.
3. Reconnect LPG power terminals to battery and start car on petrol.
4. Hold RPM at half of redline for 30 seconds. ie, if your engine redlines at 6000rpm, hold it at 3000 RPM for 30 seconds.
5. After 30 seconds while holding the engine speed at half of redline, switch fuel over to LPG, once switched to LPG and running smoothly let go of the accelerator and allow the engine to slow right down to idle for a few seconds.
6. Hold revs again at half of redline for 15 seconds while on LPG.
7. Drive vehicle for 10 minutes at various throttle positions for the LPG Computer to learn.
For the cars with the Vialle gas computer......
1. Warm up the car and make sure its on LPG before you switch it off.
2. Disconnect the blue/white wire from the Black one at the connection on the Gas computer.
3. Run a wire from the car battery positive and connect it to the blue/white wire. (Warning, dont put battery positive power to the black!)
4. Start the car on LPG and allow it to idle, the green LED should be blinking.
5. After a while the green LED will stop blinking and remain on.
6. Bring the engine speed up to exactly 3000 Rpm and hold it there.
7. Once you have it at exactly 3000 Rpm push the fuel selector switch once, the LED will blink green again. If it blinks green and red, you did not hold it close enough to 3000 Rpm and need to repeat the procedure again.
8. After 30 seconds the Green LED should stop blinking and stay on, turn off the engine.
9. Reconnect the blue/white wire to the black.
10. Drive the car around to relearn.
Might save someone from banging their heads against a wall like i did.
Not exactly information the LPG specialists freely give out.