Outer Limits 4x4 Board

Hi,
I've had my 94 80 series put on gas. the problem I now have is it runs really rough on petrol. When it was installed they replaced the O2 sensor, but found no other problems on the Dyno, on gas it runs very well returning 26lt-100km, petrol gets around 20lt-100km. When it was first done the motor struggled on petrol with a huge flat spot below 3000rpm, it is slowly improving (i guess the computer has to relearn some settings)now it has 2 small flat spots one below 2000 and one below 3000rpm. When it has been running for a long time (1/2 hour) it improves fractionly.

It went back in for a 1500km service and they found no problems on the dyno and blamed bad fuel but 3 tanks later its still there maybe getting slightly better the more it runs.
Before fitting gas they told me petrol should remain unchanged, and at the service they told me this as well. they said if the problem continues I may need to replace leads, plugs (new when gas fitted) etc...

Does this sond right? and what sort of performance do others get on gas? Either way it is so much cheaper running on gas and I'm very happy with its performace on gas, i'd just like to improve petrol a bit. I would even look at putting a dual map unichip if it would make large improvements.

Thanks Dave

There will be some loss on petrol as well due to the restriction of the mixer. Despite what they've told you.
Does yours have the air flap style air flow meter?? I'd be looking for an air leak after the air mass meter(around the mixer and ducting). The early style can be tuned a bit by adjusting the wiper spring tension in the flap style air mass meter(I think pre 96 but not sure exacly when the update occured).
These vehicles idle crap in closed loop when they get older, o2 sensor replacemnet is definetly a start, you can through manipulation of the wiper spring and adjuster get the engine to idle slightly rich of closed loop, you need the dyno to also see how its affecting load mixtures and juggle it all right.
Run premium and you can up the timing, usually about 4 degrees without a problem and it will improve on petrol and LPG.
I've also seen a couple of these with faulty fuel regs, they run lean on petrol and have low power, tend to surge, check fuel pressure.

Oh you said you have an o2 so yours has the adjustable air mass meter as the o2 was deleted on the series 2 with the new air mass meter.

Hope one of the above may help.

Joel

Thanks Joel