Only getting 16 to 18 mpg in 99 ranger, help?

[allencupit601]

I have a 1999 Ford ranger 4x4 with a 4.0, and automatic transmission. Now I recently changed out my transmission with one out of a 99 ranger with a 3.0. I had to put on my bell housing to make it work put it works great it just doesn't have the overdrive. I had the transmission already was the only reason I used it. Anyway after doing that I noticed it start to use alot of fuel so I toke it to advanced auto parts to check it out on the computer and it showed all 3 O2 sensors where bad. I changed all of them and still no better. I also gutted on my cat.convertor on my exaust. Can anyone tell me I did something right. Ha Ha

 

[Earl43P]

Make sure you didn't pinch a harness between the engine and transmission!?

 

[Hahnsb2]

Well you said it doesn't have overdrive

 

[exbass94]

Get a new cat, and this time don't gut it. No wonder the o2 sensors aren't reading correctly. They're there to monitor how the cat is working, among other things. If the cat isn't working, bam you get a DTC.

 

[vanmor]

I thought the oxygen sensors were BEFORE the cat ?

My 91 2.3 2WD only gets about 20 or so. So I'd say your doing good with 4WD and no OD.

 

[wahlstrom1]

So your complaining about getting average mileage with no O/D and throwing engine codes......

Fix the issues and live with the mileage, or buy a 4cylinder.

 

[Original_Ranger84]

Yeah you need to replace the gutted cat. The O2 sensors now have them one after each manifold and one after the cat to measure cat efficiency.

Also with no overdrive I assume you probably have an automatic transmission? You may have swapped in a 4R44E in place of your 4R55E transmission which would more then likely have a slightly different computer setup and is not shifting properly.

 

[v8318cid]

The O2 sensors were only before the cat prior to OBDII. Once OBDII became mainstream, a sensor was added after the catalyst (or each cat if you had more than one, such as a dual exhaust setup). The idea was to verify catalyst operation. Once below an acceptable threshold, the CEL would illuminate to indicate time to either change the cat, the O2 sensor, or both. As a side note, it is also intended to discourage people from gutting or removing the cat (illegal by Federal emissions standards, not to mention what would happen in CA or NY which are far worse...). If removed, the CEL illuminates and engine performance (read: fuel economy) will suffer.
By the way, did the 4.0 litre ever get better than 19 or 20mpg anyway? I know the new models are only rated 14/19.