Land Cruiser 105 fuel issue

Submitted: Monday, Mar 13, 2006 at 21:07
ThreadID: 31709 Views:34789 Replies:3 FollowUps:4
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Howdy, my 2000 Landcruiser FZJ105 (4.5 petrol) manual wagon with 120K on it has developed a drinking problem (bit like its owner)

I used to get around the 18l/100km mark from it but it has jumped up to the 25 mark of late. Strewth!!!!

Now I know they are thirsty, but having owned two 4.5 Cruiser's and one 4500 petrol GU Patrol I know something has gone wrong with this one.

Apart from "buy a Nissan" or "buy a diesel", can anyone actually offer some useful advice?

It runs superbly, has a new Ryco airfilter (the 255mm TD one), has always run on BP Ultimate PULP or LPG, has had the valves adjusted by a LC specialist, is well maintained etc....... Sometimes I swear it is running rich from the exhaust smell but I'm buggered if I can work out how as from what I believe the 1FZ doesn't have O2 sensors.

What would cause a spike in fuel usage in a 1FZ-FE donk? Anyone????

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Reply By: 4145derek - Monday, Mar 13, 2006 at 21:30

Monday, Mar 13, 2006 at 21:30
Hard to say my 1100 is just as thirsty and can't do much about it.

Plugs, filters and tyre pressures don't do much.

A/C use and the roof rack do affect the consumption.

Other than that there is no real adjsutment. There is a mixture pot at the R.H. fender but I have read, been told and done some investigation that it must be left alone unless there is a problem.

Regards Derek
AnswerID: 160297

Reply By: Scoey - Tuesday, Mar 14, 2006 at 17:08

Tuesday, Mar 14, 2006 at 17:08
Hey V8,

I'm not an expert but my 1FZ-FE has O2 sensors in the exhaust. Don't know if this helps - but your post indicated that you thought that motor doesn't have them. Oh, if it matters mine's a '94 80 series 1FZ-FE and the O2 sensor is pretty much under the front drivers seat floor in the exhaust but when my sensor died the truck ran sh*thouse!

AnswerID: 160466

Follow Up By: V8Diesel - Tuesday, Mar 14, 2006 at 18:54

Tuesday, Mar 14, 2006 at 18:54
Cheers for that Scoey. I'm led to believe that the 105's don't have an O2 sensor at all but will get further underneath it tonight and scope it all out.

FollowupID: 415272

Reply By: rod2101 - Wednesday, Mar 15, 2006 at 09:58

Wednesday, Mar 15, 2006 at 09:58
100 Series 1fz-fe has no 02 sensor and runs in " open loop " all the time so it cant trim the mixture. Any sensor giving false reading could cause mixture to be wrong. The most likley ones are engine temp sensor (on block passenger side I think ?) and air temp sensor ( on air duct near air cleaner, reads between 300 ohms and 4000 ohms depends on air tmp but usualy about 1500 ohm ), maf sensor ( measures engine vacum ) or fuel presure regulater. Check all vacum pipes for leaks .

I put a 820 0hm resistor in place of the air temp sensor and it made a dramatic improvement to fuel economy and went much beter in the higher rev range !
All landcruiser 100 1fz-fe engines apear to be " set " rich !

Regards Rod
AnswerID: 160602

Follow Up By: V8Diesel - Wednesday, Mar 15, 2006 at 10:10

Wednesday, Mar 15, 2006 at 10:10
Rod, you are a legend.

It all started about the time I backfired my LPG at about 400RPM whilst slugging up hill. A damaged sensor would explain the sudden increase in fuel consumption by 'tricking' the motor into running rich..

I will give it a thorough check out on the weekend with this in mind. The actual resistance figures quoted are invaluable mate.

Since you've fitted the 820 Ohm resistor, have you had it on an exhaust gas analyser? Hate to lean it out too much - there's a lot of valves to burn in the 1FZ!

Thanks again Rod, much appreciated.
FollowupID: 415426

Follow Up By: V8Diesel - Sunday, Mar 19, 2006 at 13:46

Sunday, Mar 19, 2006 at 13:46
Hi Rod, fitted the 820Ohm resistor to the air intake sensor as suggested. I am certain the motor runs better already. I will so some consumtion testing over the next few weeks.

Only concern is that I may be running it too lean. Have you had yours on an EGA?

FollowupID: 416220

Follow Up By: rod2101 - Monday, Mar 20, 2006 at 09:40

Monday, Mar 20, 2006 at 09:40
I have not had the exhaust measured but the spark plugs don't look like they have been too hot. With a fixed resistor in place of the sensorit is not ideal as the injection system has lost its ability to correct mixture for changes in air density (air temp), the colder the air outside the leaner the fuel mixture! An improved way is to add a 1200 ohm resister across the origional sesor, this will give you a leaner base setting and can lean out further as the air temp increases. This is what I have done and has worked very well for me. Highway economy sits around 16lt100ks (used to be 18-20lt100ks)with "at" tyres and family of 5 and all there gear.
FollowupID: 416338

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