Bad Fuel Consumption

I have just recently bought a 1999 Jimny and it has only been getting 20L/100km (200km to a tank) so as you can imagine it's kind of a hassle to pack up for a weekend and go away 4x4 and camping.

I have done simple things like check for vacuum leaks, replace O2 sensor, replace spark plugs and replace air filter
Replacing the air filter I took the whole air box and piping out and did a full clean out giving the car more power but not helping with fuel

Just wondering if this is a common thing with the jimnys and if anyone has had similar problems

Blimy that's 124 miles to a tank! That's mega bad- I get 180 tops and that's bad..... Some people on here get a fair bit more too. Sorry I can't offer a solution as you've tried the obvious bits, I hope you find the issue soon though!

just checked mine( a 2002 1.3) just got 143 mile to 20 pound or 36 to the gallon. have you done a service lately?

My Jim averages about 30 -32 mpg. I do a lot of short trips.

Have you checked the easy stuff, like air filter?

my G13BB was getting incredibly bad mileage. i tried all the obvious stuff as you wrote, in the end i believe it was due to the manifolds being really sooted up. when i did the engine swap i cleaned them out with carby/throttle body cleaner.

one way to see if this may be your issue is to remove the pcv valve on the rocker cover to the air intake & see if it is fouled at all, mine was blocked pretty well solid.

random image from internet of one:

Have you been over the brakes and made sure nothing is binding?