gramps replied:

Sir_Gibbo,

Not being that mechanically minded I can't help you with the first part of your post, however, the second part may give some clues.

I run a 3.4l V6 and can push it up to nearly 14l/100ks fully loaded around 100-110kmh on country runs. In normal suburban/semi-rural (definitely not stop-start city runs) I average around 11.5l/100k. That's at a normal total weight of just over 2,000kgs.

Boo replied:

Hi,

We had a very similar problem with our Patrol dual fuel, no problems on gas but sounding almost identical to your problem on petrol.

It ended up being the fuel pump in the tank, it was still working partly, so we were able to drive at low revs, however as soon as it was under load there wasn't enough fuel getting through to power it. We had the pump replaced and now works fine again.

May or may not be your problem, however might be worth a look.

Regards,

Kerrie

GaryInOz (Vic) replied:

Any ECU codes??

My theory (FWIW):

Try resetting the ECU, may have gotten itself in a knot. Disconnect the battery overnight and reconnect in the morning. For the next 3-4 tankfulls run on PETROL ONLY. This will allow the ECU to "learn" the operating characteristics of the fuel system/ignition system/emission system on petrol. Most gas fitments to EFI motors have a box (*) that modifies the "point" signal used to fire the ignition coils when using gas.

I'm guessing that what has happened is the battery has been disconnected when they did the installation, and you have used it on gas for most/all of the time the ECU is in it's "learn" mode. LPG burns differently to petrol, and your ECU was inadvertantly callibrated during the learn mode to run on gas instead of petrol (affects ignition timing). Switching to gas switches in the abovementioned box (*) and modifies the timing even further, explaining your poor gas and petrol consumption and poor performance.

Not absolutely sure, but plausible.......

J.T. replied:

Perhaps the injectors are blocked due to carbon from gas use.If petrol is not used regularly the injectors nozzles block.I agree also the fuel pump or filter(cheapest fix first)could be buggered.

4runner replied:

Hi. I have a 1991 V6 4Runner and find that it is a thirsty little sucker. The best I have had out of it was 12 litres per 100 Km , but on an overall average 13 -14 litres per 100Km is about as good as it gets. Yes, you do have to row the gearbox at low speeds, and on climbing long hills one has to drop from 5th down to 4th. From others I have spoken to about the lack of performance at low speeds , this is normal for a vehicle that weighs in at approximately 2 1/2 tons. Thats nearly 4000 Lbs in Imperial measurement. One thing you should do as others in this forum have suggested, is to replace the fuel pump and also the fuel filter. Failing that then get the fuel injectors checked and cleaned. But for HEAVENS sake if you have to replace them , whatever you do dont buy the injectors from Toyota, as they quoted me $260 per injector. Multiply by 6 and you will see what I mean. Repco or other good quality aftermarket accesory shops can do better than that in terms of price.
Oh and before I forget, have you checked your air filter element????? Its placed in the most ridiculous position, right behind the left hand head lamp and therfore sucks in every conceivable bit of dust and dirt. A snorker would be a better proposition. Hope that has been of some help.

awill4x4 replied:

If ever a motor is crying out for an exhaust change to free flowing headers/extractors then the 3.4 litre V6 Toyota motor is it. (don't know about the 3.0 one though)
For a modern twin cam V6 the exhaust on these is an absolute shocker. (Just poke your head under the bonnet of one and look at the exhaust manifold and you'll see what I mean) I would expect considerable gains in both power and economy by a properly designed header/extractor system.
Regards Andrew.

4runner replied:

Hello Sir_Gibbo. What I forgot to mention is that mine has got a 2 3/4 inch mandrel bent stainless steel exhaust sytem from the manifolds all the way to the tail pipe. Thats helped get rid of the exhaust gases a lot quicker - oh and does it sound good !!!! The larger exhaust system has helped improve economy since it was fitted several years ago. A snorkel is the next thing that is going to be fitted in order that the motor can breathe cleaner and cooler air.