1988 FJ62 eight miles a gallon? help

[concorddesk]

I have replaced all seals and gaskets - valve cover as I still need to adjust the valves.

After I replaced everything I got aboout 17mpg for two months.
I am now getting no better than 8mpg.

What could cause such a sudden change in fuel consumption?

engine light is not on...
running a/c does not change...
I have converted to electric fans...

I thought it could be oxygen sensor, but no engine light?
I thought maybe the engine temp sensor but it seems to be reading correct..

any thoughts.... Thanks Dave

 

[RockDoc]

Same tire size and driving habits? Any changes in how it runs/idles that would suggest something in the EFI? IIRC, some have reported an improvement after giving the fuel pressure regulator and the pulsation dampener some attention.

Have you done tune up stuff recently? (air filter, check plugs, run some injector cleaner, fuel filter.......)

Try checking for codes (paper clip), IIRC, you can get some codes without tripping the check engine light.

Some have reported good things from changing out the O2 sensors, I believe they are supposed to be replaced after the first 80 000 miles anyway. Try searching for 3FE and sensor and see what comes up, might be more in the 80s section.

 

[cruiser88]

I have replaced all seals and gaskets - valve cover as I still need to adjust the valves.

After I replaced everything I got aboout 17mpg for two months.
I am now getting no better than 8mpg.

What could cause such a sudden change in fuel consumption?

engine light is not on...
running a/c does not change...
I have converted to electric fans...

I thought it could be oxygen sensor, but no engine light?
I thought maybe the engine temp sensor but it seems to be reading correct..

any thoughts.... Thanks Dave

Yes rockdoc is spot on check for codes ....check your FSM for details.

You could have bad fuel pressure regulator ,O2's..etc . I bet if you check codes you will find something allowing you to run rich after warm-up.

Also check your spark plugs to see if they are fouled up.

 

[cruiser88]

OH yea.....check for codes while its still hot...not running of course

 

[concorddesk]

I will pull codes Monday to see if it will give me anything. I have same driving habits and tire size.
thanks I will check codes and go from their.

 

[Randy88FJ62]

Your first post mentions that you were getting 17 mpg? That seems crazy high to my usual 10 mpg.

 

[dwillmo]

17 mpg!!!

Nothing seems to change mine from about 10 to 11, depending upon how much towing I'm doing, and that doesn't seem to make much difference.

 

[kuma]

Wow 17 thats what my 62's previous owner said he was gettin. But my self its more like 10 to 12. I then tightened up the regulator on the back side of the engine under the little grey cap and changed the fuel filter on the fender well and filled up last night got 16.7 miles per gallon yeppeeee.................

 

[concorddesk]

I was getting 17+ mpg no lie, with no change in driving habit it became very low.