I have a CRX Si which was gettting 31MPG in the city, and it has slowly gotten worse.

It is down to 21 MPG and if you stand behind the car you can smell the gas in the exhaust.

I/H/E are the only mods.

Anyone have ideas.

We have already changed, plugs, wires, vacuum lines, O2 sensor, fuel filter, distrubtor cap and rotor button. It has not gotten any better.

 

My tps sensor being off created mileage problems....it took me FOREVER to figure that one out. I had to go OBD1 and Hondata to see it on the computer while tuning it...LOL

 

Are all the parts you replaced are OEM? Have you checked the timing?

Tire pressure been checked lately?

Replace the PCV valve.

Purge the coolant of air, remembering it may take 40 minutes or more for the fan to come on twice, per the owner's and shop manual procedures for purging.

Put a bottle of Chevron Techron in a full gas tank. Drive until the next fillup. Repeat 3x. Fuel injectors can get dirty and not inject right.

Consider new --

-- thermostat, so the engine is warming up in a timely manner.

-- ECT sensor. The ECT sensor apparently dominates in determining when the engine switches from open to closed loop, for one.

-- distributor housing. The housing holds three engine sensors. I think these sensors' wiring, coils and/or reluctors degrade over time.

A little more is at http://honda.lioness.googlepages.com/gasmileagetips

 

Also depends on how you drive it.