Lancruiser 4.5 EFi ECU and Diagnostics

[OzPumba]

I have a Landcruiser 4.5 EFi 1998 commonly referred to as 1FZ-FE4.5L Petrol I6 or FZJ105. I had dual-Fuel (LPG) conversion done to the vehicle but noticed that on big throttle openings, it's prone to backfire which causes a very expensive air box explosion. This only happens with LPG and not running on petrol.

The usual 10,000km service dictates taking the vehicle to the Toyota dealer for the petrol tune-up and service where the performance is optimised for petrol usage. A subsequent visit to the LPG boys is required to re-tune and optimise performance for LPG. As the vehicle runs on LPG most of the time (ratio of 4:1) this type of tuning regime is quite normal.

Contacting the LPG boys when the first backfire occurred, they claimed that the spark leads are at fault. Now I’m no genius when it comes to vehicles but I’ve been around the block and even rebuild and converted a VW car from a carb fed VW engine to fuel injection. The primary reason for backfire is incorrect ignition timing. Taking the vehicle to Toyota to check the said leads proved a waste of time and money. Replacing the said leads just to make sure was yet another waste of time and money.

Sorry for writing a book but I believe background info is important to paint the entire picture.

Now, to get to the real issue at hand, I decided to purchase an OBII compliant diagnostic tool after confirming with a tech guru where my car is serviced by the way, that this vehicle is ODBII compliant. I needed to confirm what was going on when running the vehicle on LPG and why the backfire occurs. The diagnostic tool did however NOT work and subsequent emails to Toyota Australia confirmed that only Landcruisers 2002 models and onwards were ODBII compliant.

Where to now? Toyota service centres have a proprietary diagnostic tool so how do I diagnose the problem? Is there a way of replacing the ECU with a newer version that is ODBII compliant? Can I go to the wreckers and get a post 2002 ECU and put it into my car with minimal modification? Can anyone suggest what to do other than the addition of a piggy back ECU coasting $950 plus? Is there an ECU replacement I can install on this car?

I hope there is some Toyota whiz kid working at Toyota that could steer me in the right direction.