I just did a tune up on my 1994 honda accord...it has 100,000 miles exactly, i use iridum plugs, msd wires, new distributor cap, rotor, fuel filter, etc. I am still getting poor gas mileage. I am getting 20 mpg on the freeway.

I just went for a California "dyno" smog, and it barely passed. It did 700 noX, when passing is 696. This was at the 15mph test..It passed VERY good at the 25mph test.

You guys think I have a bad o2 sensor, or a bad cat?

thanks

 

umm if you never changed the o2 yet since you got the car, change it! ignition timing can be next thing ya check, compression test, pcv vavle check. injectors check.

 

ok..ill change my o2 sensor..it isnt too bad..only $100.00 or so through a local vendor..for a bosche.

I changed the pcv valve, checked compression, everythings checks out fine. I am thinking o2 sensor, or catalytic converter.

 

from the manual it says to check for a clogged cat. converter...

a. open throttle until engine is at 2k rpm
b. release throttle quickly.
c. if no restriction, throttle will quickly drop nomore than 2 in-Hg or more above normal.
d. if it does not show 5 in-Hg or more above normal reading, or momentarily hover around its highest reading for a moment before it returns, the exhaust system or the cat. converter is plugged ( or exhaust pipe is dented or core inside the muffler has shifted)

came straight out the books... hope this helps.

and o2's cost a little extra at auto stores because its plug and play... if you want to save urself some cash, they have one where u need to use your existing wires... save urself like 40-50$'s... that can go to gas$! damn the government!

 

before you go out and spend that money.. check your coolant temperature sensor.


Modified by mistersparco at 10:03 AM 4/9/2004

 

there is a post going on about bad milage with iridium plugs. Maybe you should go to platinum instead. With my old car, I got like 33 mpg highway with a full carload of crap and platinum plugs. Was a good car.

 

Those iridium plugs seem to be a culprit, try the usual ngk v power plugs, they perform really well and are a great buy for the price.