Hi guys! New on this forum, but i hope someone out there can help me.

I've searched for similar problems on this site, and some do sound similar, but not the same. I'd like to ask for some opinions as to what the problem might be.

I drive a 1999 Commodore Acclaim (auto) with 140,000km and about a week ago, after filling up with a full tank of fuel from my usual servo, i noticed my car revving a bit 'differently', but not the same as if the transmission was low on fluid. I put this down to being a bit heavier in the rear due to the full tank of fuel.

About 250 metres down the road, the orange 'engine warning light' (left of the dash) came on. I pulled over, turned off the car, checked the fluids (couldn't think of anything better to do), all was fine so i restarted the car (light was off) and kept driving. The same problem with revs and a few km's later, the light came on again. Stopped, restarted, all was fine, got home okay.

The car seems to 'drift' around in rpm's and lags when accelerating. I can carefully get up to 60km/h and hold it there, but the tacho will drop or rise around 500rpm suddenly, causing the car to vibrate a bit. Eventually, the engine warning light comes on again and acceleration is really bad. It seems to shift okay, but sometimes it will shift late, revving to 3500rpm before i even get to 60km/h.

I've considered dodgy fuel, but my partner filled up at the same time from the same pump and her car has had no problems. She drives 2000 VX Commodore.

Since then i've had an old-school mechanic look at it, but the best he could do was replace the fuel filter and recommened i should have a Holden dealer look at it.

Perhaps the worst thing was yesterday, i gave the car about a 150km test drive (all sorts of driving) and it behaved ABSOLUTELY fine!?!? Then this morning after driving for ten minutes, it all happened again.

What on earth could this intermittent problem be?

Thanks in advance.