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No, a compression test should be substantially cheaper.
If it runs fine on petrol the motor wouldn’t be suspect to me, it’d be something in the LPG delivery system. LPG could potentially make an existing problem slightly worse, but it wouldn’t create an entirely new problem with its runability, as far as the motor itself goes.
Long shot, is there a place that does LPG conversions local?
Ditto. Since the engine runs okay on gas, I would appreciate that now and work on getting it in top shape. Ignore the LPG now until you know everything is in great shape engine wise.
Because there is an unknown issue about the LPG running, I'd suspect tune up parts like the spark plugs and wires. Since the 1990's when the OEM began to push 100k mile service intervals with warrantee, owners stopped changing plugs and the plug wires often enough. Now there are millions of vehicles that have very old plug wires and plugs. Those are fragile parts that used to get changed every few years or 25-50k miles. I've bought two 98 Explorers in the last four years, both had the original plugs and plug wires. One did fine after I replaced them, but the last one ran worse inexplicably after doing the plugs(a worse miss). That turned out to be one coil pack, which can be ruined with huge plug gaps.
So, if you do not know how old the plugs and wires are, I would change those now for sure. They don't have to be high dollar parts, just good quality not cheap junk. Ideally you'd want Ford wires or similar $80 up type, but a top brand from a local part store will do fine for now.
I'd clean the IAC, that's a 15 minute job, or less for a mechanic. It would be good to have the computer scanned at the OBDII port, for any error codes. Some vehicles don't display a dash light to tell you there are some codes.
You want to know there isn't anything minor, or possible to do for the engine now, when you again ask for help with the LPG system running. Be sure all fluids and filters are full and fresh, and it runs well and starts well at all times. You don't want a mechanic to toss new possibilities like those at you. If those haven't been done, then they tell you it could need those, or the new engine crap.
The compression test, or a leak down test(which is better but slightly more involved), those identify the cylinder pressure possible. A worn out engine will have failures from those tests, which can point to bad valves, seats, or worn piston rings etc.
You do not want the engine to come out, it sounds like over there they are too quick to yank one and sell the customer something more. Part of what is a weakness of the SOHC engine is the quality of the timing chain parts, and the expertise of installation, plus parts quality.
The original engine is very good except for the longevity of the timing chain guides and tensioners, which has been mentioned before. You want to have everything else in excellent shape, and then concentrate efforts on those timing chain parts. If the engine shows no symptoms of chain noises, that would be best case, and just changing the external tensioners is a great maintenance step, leaving possibly 100k more mileage until the next worry about those parts.
www.supercheapauto.com.au
Abusive middle eastern thugs in jail don't faze me in the slightest...but these guys confuse me. All at sea I am:-(
