Did I cause this?
 

I am wondering if I caused this problem? A couple of tanks ago, I put reg. 87 in (needed gas asap; couldn't fine a station with 93) Well, since everything seemed to be ok, no immediate CEL or bad starting, nothing ran just as smooth as with 93 gas. I put a few more tanks of the reg. 87 in. Now, after switching back to 93, I have a few codes poping up.

the codes are: P0154 (o2 pass. #1) P1300 (fuel sys. or miss fire) P0308 and P0302 (miss-fires in #2/8 cyl. So, I'm wondering if running the 87 gas has caused this problem or is this just something that has happened...
thanks again.

And you had to ask????????????????????????
How many miles on your truck and has it ever been tune along with wires?
You are easily loosing 2 MPH plus a huge amount of low end torque, much lee carboning up your engine.

The truck is a 2000 with 136k and I believe at 132k land rover of greenville, sc. did a tune up on her.

I miss spoke; truck did not have tune up @ 132k. unknown when was done last.

see mikes 60k service in the HOW TO section and use 93 or 91 gas from now on.

I'm not sure if just a few tanks of regular would give you misfires and kill an O2 sensor. When you had the tuneup did they do the wires?

I doubt the low-octane gas was the only thing responsible... there are so many Disco's running around with people driving them who don't know the need 90 or better...

definitely could have been a contributing factor but i'd look to your plugs and wires first

he just needs a tune up, and most likely wires and plugs.

Its likely that you just have some carbon buildup somewhere in your engine, try running a can of seafoam in the gas tank, as well as through the induction.