Horrible mileage

[Dattebayo]

Hey guys, I'm getting about 18 mpg combined and around 12-13 around town. Where do I start in improving this? The truck has a three-inch drop and some possible driveshaft play due to either a bad center bearing or a worn U-joint. Alignment has been checked and is okay, engine seems to have decent power also.

[AZhitman]

In what? Hardbody?

[Dattebayo]

Yes, the truck i have listed on my profile. People I have talked to tell me I should be getting at least 25.

[AZhitman]

SOHC KA? 5-speed?

[Dattebayo]

Z24 engine, automatic, 2WD.

[AZhitman]

Standard stuff... Got the FSM?

IIRC, those suffered from horrible FE when they had issues with the ignition (secondary coil) - Check spark from both, and ohm out your plug wires (they don't last forever). After a full tune-up (including compression test), check the AIV (they clog) and the sensor at the manifold, and also check valve clearance (hot). Check the 2 terminal water temp sensor. Tons of variables, any of which can really impact FE.

[Dattebayo]

So, a standard tune-up should do it then? I am surprised to learn that could make me lose up to 6 points...

[AZhitman]

Dude, any/all of those could conspire to cost you WAY more than 6mpg.

[Dattebayo]

I see, you edited the post. Welp, I'll give it a once-over tomorrow. I can check everything except the valve clearance or compression with what I have now...

[Rev_D21]

Do you have a vacuum gauge? If not buy one, it will be a great tool in checking the condition of your engine. The Z24i had miles of vacuum lines and if each one had a tiny pin hole leak it would add up really quick to poor performance and low MPGs. Buy a cheap gauge and learn how to read it.