new here,91 explorer, 4.0L running rich, bucking, other probs...

[whtexploder]

hey eveyone, got a 1991 ford explorer recently it has a 4.0L with a auto trans. the cel light came on and it was running really crappy bucking like its misfireing, and running super rich, i can see the smoke, geting like 6mpg or so.

i did a code check and it came up with 41 and 12 codes koer

i have changed the coolant temp sencor, and the t stat, after i changed the t stat the temp started reading, it wouldnt before.
also just had a new pump and fuel relay put in.

i was thinking possably the cat was cloged because the exhaust started leaking in spots really bad and it runs super rich... also the idle fluctuates but that could be from the code 12 iacv. 41 is running lean for more than 15 seconds, and idk how its running lean... another reason for thinking its the cats is the guy that had it before said its been geting at best 9mpg for a while, so i was thinking the fuel cloged the cats up... the vehicle had a full tune up in march...

any help would be much apriciated. thanks -blake

 

[YBCold]

have you checked your O2 sensor?

 

[whtexploder]

i havent tested it to be bad, but also i went back and re checked the koer codes and it was a 42... im going to clean the o2 but i dont see why it would run this ****ty because of the o2. im puting a piece of straight pipe in to see if it helps...

 

[MrQ]

The O2 sensors tell the computer how much fuel is going through the exhaust and the computer decides to either go more lean or more rich. If they are bad they will be sending false positives to the computer. Its not a good idea to remove them especially when they are relatively easy to replace.

 

[MrShorty]

The books recommend that one of the first tests for most O2 sensor codes is to test fuel pressure. In this case, where the O2 sensor seems to be accurately seeing the rich condition, I'd probably start by checking fuel delivery.

 

[KobeJ05]

i havent tested it to be bad, but also i went back and re checked the koer codes and it was a 42... im going to clean the o2 but i dont see why it would run this ****ty because of the o2. im puting a piece of straight pipe in to see if it helps...

o2 sensors can cause issues!