4.5L on Gas problems

[Hanna]

Hi All i'm new so this is my first post
My folks have an 1994 cruiser Auto on gas and are about to give up trying to find the source of the problem. Since we bought it was have done 200,000km without any problems until now, in the last few months the car has lost power severely, even the dealer said it was one of the worst they had seen!. The truck has 300,000km on the clock but only the last 120,000km have been on gas. The dealer diagnosed it as the O2 sensor but 400 bucks later and no difference. It is not the gas system as it is gutless on petrol as well. We dont think it is the auto because with the torque converter locked in 4th the car wont even hold a headwind without dropping to 3rd. When floored the car will rev hard (to 5000rpm) but will only slowly accelerate.

Thanks in advance

Hanna

P.S the truck has a safari snorkel and extractors we were told it could be the air flow sensor.

[RV80]

Does it stall, run rough, hesitate at all?

[the_smoo]

are the leads the original set?

may pay to check/replace them..

[skootin]

Valve clearance should be checked regulary on engines fitted with gas.

[Hanna]

Hi all and thanks for your replies

The car runs fine starts instantly never stalls and no hesitation. The leads, plugs, air filter, muffler and oxygen sesnsor have all been replaced recently still no difference. I dont think this is going to be an easy fix because even the dealer can't diagnose it. The rocket cover has never been pulled off the life of the motor but when the plugs were changed a compression test was done with 190kpa on first turn on all cylinders. We are just hoping its not the auto as that can cost around 4K to rebuild

Thanks for your replies

Hanna

p.s i forgot to mention when the problem started fuel economy on gas went from 25L/100km to 33L/100km we now get around 295km to 90L of gas which is very bad!

[dow50r]

You need to do a systematic diagnosis....firstly, it is apparent on both fuels...so it is common and not one or the other....
If it is not a precleaner stuck in the snorkel, or an inlet filter blocked, then it may be the muffler has collapsed inside...
I would point to the flow meter, only the motor would run rough....might still be worth taking off and seeing if the flap is free. It should spring back to closed easily....
A compression check of the motor will see if any valves are leaking...if you dont run valve saver, or more to the point...if the valve clearances have not been checked for a whie...this could be your culpret.
Andrew

[The Fish]

My money's on the valve clearances especially if the rocker cover has never been removed. An experienced gas fitter would/should recommend the valve clearances be checked before or as part of fitting the gas to the Yota 4.5 litre motor.

[dow50r]

My money's on the valve clearances especially if the rocker cover has never been removed. An experienced gas fitter would/should recommend the valve clearances be checked before or as part of fitting the gas to the Yota 4.5 litre motor.

Yes, and recheck every 40.000km after that...i know people who have found out the hard way....usually means you loose a cylinder though...
Im on the flow meter...especially if its been backfiring when starting hot!
Andrew

[Hanna]

Hi All and thanks again for your replies

We thought we could rule out valve clearence and head problems because of the good compression test results (190kpa on all cylinder). The car has never backfired and is extremely easy to start on gas (less than one turn) Cant be the muffler because its brand new and cant be the air filter because its new as well. As the conversion was done by a home mechanic valve saver was never installed, also my dad is a gasfitter by trade so he ran the gas lines and mounted the tank (its a used kit off a nissan patrol) himself. So yes the car has not been well maintained on the gas side of things (no valve saver or clearence checks) but we thought if it was the head it would show up in the compression tests. Thanks all for your replies

Hanna

[RV80]

If the gas kit is off a pootrol and hasn't been tuned
properly for the big 4.5lt then that could pose a
problem. I would take it to a gas expert.

[Hanna]

I dont think its the gas sytem because it has no power on petrol as well, also the gas system ran fine for 110,000km so i think its tuned right. dow50r made a good point that it could be a blocked snorkel (pre cleaner) i will check it tonight.

Thanks for your replies

Hanna

[dow50r]

Hi yes most of what i said you have already done....if the gas system starts on petrol at all times, thats probably why it starts so well..and its also a good way to not get any backfires.....that would make it a fairly new (less than 8 years old) gas system with a computer to control the gas....the oxygen sensor controls on these gas systems aswell...trimming the fuel mixture.....if you dont have any luck with the snorkel, PM me and i will send you up a spare oxygen sensor to try....sometimes they get lazy without setting off the check light.
Andrew

[dow50r]

I dont think its the gas sytem because it has no power on petrol as well, also the gas system ran fine for 110,000km so i think its tuned right. dow50r made a good point that it could be a blocked snorkel (pre cleaner) i will check it tonight.

Thanks for your replies

Hanna

Only if you used those sock pre cleaners that seem to get sucked into the snorkel.
Andrew

[Hanna]

Hi again and thanks for the replies

The gas system is a very simple one which is independent of the petrol system. It starts on gas not petrol becuase the gas system is quite old, the ecu has minimal control when the car is on gas. Thanks dow50r for the offer of the oxygen sensor but it already has a new one which did not improve performance, there is no pre cleaner on the snorkel just straight into the air filter box. Although this car has been extremely reliable until now (not many cars do 300,000km wihtout ever touching the driveline! especially an AUTO) I think my folks are just going to give up and trade it in on a ford territory.

Thanks

Hanna