Engine cut-out on petrol around 3000rpm

[vscalais995]

Hey all, i have a 95 VS calais on factory LPG and Petrol. I'm having an issue with the petrol that i cannot figure out. When driving the car on petrol it runs fine until around 3000-3500rpm when the engine cuts out very harshly completely dropping down to pretty much 0 rpm and sometimes stalls, Feels almost like it just looses all spark. Even once or twice it has cut out at very low revs under breaking.

However when the car is in park it will sit on the rev limiter happily. When on LPG the car runs fine though!! Had the fuel system checked and its alright, no error codes from the computer, tried a different AFM (air flow meter)
only thing i can think of that would effect only the petrol under load is some sort of elecrtical fault or earthing fault......perhaps earthing fault in injectors?
any help is GREATLY appreciated thanks

[VrWagz1]

A bit more info around the cutting out time is maybe needed. Does it recover from this after it drops to nearly 0 rpm or do you have to switch off and start again. But at a first guess yes i would be thinking of an issue with the injectors. I would start possibly by pulling the fuel rail out and check its not full of crap. Also if fuel pressure regs are cheap, i would swap that out so that it can be discounted as an issue.

[monkeys437]

Possibly alternator on the way out and not supplying enough voltage under load..... could be worth checking

[vscalais995]

vrwagz1: yeah it revs up normally and cuts out and JUST regains an idle.....ill go give the injectors a look now but seeing how it has no issues reving in park or neautral wouldnt that mean its getting enough fuel? Cheers

monkeys437: Possibly alternator on the way out and not supplying enough voltage under load..... could be worth checking....
it couldn't be a voltage supply could it?, seeing how its running perfect on LPG?

[VrWagz1]

I'd def say no to the alternator, as it only tops the battery up really as a primary function. For this to be an issue, you would have to take the battery out of the car and have the car running off the alternator only....then have the alternator buggering up at 300rpm. Providing you have a fully charged battery, you can drive for a good hour or so without an alternator at all, and it works fine(Ive been there).

Reving in Neutral ect...

Not nessacarilly, because reving in neutral dosnt need much fuel, as the motor isnt generating a heap of power at that moment in time to also move a 1.5ton lump with it, thus it dosnt need/use much fuel. When ur reving while driving, you use considerably more fuel due to the motor having to generate a whole lot more power to move the whole car.
Justa quick question, have u replaced the fuel filter? That would actually be the first port of call before you go much further. Just thinking out loud, if the fuel filter is blocked up a bit, you maybe getting enough fuel to rev up to 3000rpm but then the fuel lines empty out due to the blocked filter at the rear of the car....then it takes a few seconds to build up fuel and pressure in the lines again just before the car stalls.

[vscalais995]

yeah ive had the fuel system looked at, filter cleaned and pressure tested at both ends of the system but if you think it could still be that ill pull the injectors/fuel rail out on the weekend and have a look???
im still really thinking an earthing or electrical issue on the petrol components ie injectors??, but from what ive checked so far everything seems to be alright. like drawing current upto a certain point under load till when it faults and engine cuts out...
any other thoughts let me know to, thanks for the help

[VrWagz1]

Ahh k, kewl, there goes my theory. I have heard of electical issues with engines under load. Espcially if the engine mounts are broken, the engine can twist around quiet a bit and pinch a wire somewhere. But i had a dud fuel pump once a few years back, It used to cause the car to not rev past 4500rpm. Slightly different issue but turned out just to be a worn pump. One thing i did and you can to, is borrow an electric pressure gauge off someone if u have access to one, and rig it into the fuel line and whatch the gauge as you go for a drive to see that you are/arnt losing pressure. That'll help you get a start on where to look. Thatll help you see if its fuel or injectors or even neither!

[vscalais995]

haha yeah i just can't figure this one out.....yeah ive had an electric pressure gauge hooked upto the system whilst its been running nothing pressures normal...not even the mechanics ive been to really know, we were pretty convinced it was AFM but na that was fine, and like i said no error codes off computer.
hmm interesting with the engine mounts, ill have a look tommorow, also i was driving it before and it seems to cut out at really low revs sometimes when cornering it seems, but that could be the engine using more power due to power steering, again pushing me towards electrical. I'm just out of ideas haha

[STK096]

I have just stumbled across this thread looking for answers for the same question! I have replaced so many parts.

I car is also on LPG.. all the same side effects!

vscalais995 did you ever find a solution? I too am thinking electrical. Knowing how all the LPG is wired in, i am thinking it could be a relay issue. Maybe it could be worth buying a few and trying it, they are quite old now afterall.