poor gas mileage I need help!

[set7565]

My '90 lx 2.3 liter with a 5 spd I have had for about six months now, I've tuned it up with a new: cap, rotor, plugs, wires, K&N, and new muffler and tailpipe. It only has 70,000 original miles, runs fine, power wise, but it'll only get about 12mpg city, and about 18 highway. A 5.0 doesn't even get that bad! I do take it a little high(3500-4000 rpm's) but shouldn't I be getting better? Please help me I'm stumped.

 

[Cougar]

Get the codes pulled out of it at autozone or somewhere.

 

[Dan P.]

Have you replaced the O2 sensor? And also try the fuel filter.

 

[set7565]

Still crapy mileage in my '90 lx

I replaced my fuel filter, and I have a new o2 sensor. I ran a scanner on it and it stated that the o2 sensor voltage was low, how do I fix that, is the oxygen sensor faulty?

 

[Gotta91LX]

I would check your PCV valve.

Wayne

 

[Dan'l]

12/18 leads me to believe the computer is on limp home mode. Spend the $20 or so and get a code reader. Let us know what it says(flashes). To put this in perspective, I regularly get 26+mpg on my 91 which sees the rev limiter at least 5 times a week. Years back I had a 1968 firebird which we transplanted a 66 425 olds into which regularly saw 21 mpg - (or 4 mpg if you had an awesome night) but it usually ran 18 to 21 mpg. Is your timing belt still in sync?

 

[1992 2.3LX]

i get 26 mpg and i have 155,000. what type of o2 ensor did you get??

 

[set7565]

o2 sensor

i get 26 mpg and i have 155,000. what type of o2 ensor did you get??

I have a bosch o2 seneor, and it's only about three months old.

 

[ka0tyk]

just because parts are NEW doesnt mean they are GOOD... run codes and see what your computer is thinking.