melitza03

Head cracked on my D15B7 at 186k. Decided to swap to a JDM engine in hopes of getting a lesser mileage engine that would last longer. With the old engine, I always got around 40mpg; now, a year later, I'm never over 26mpg.

What's changed between my 40mpg blown engine and the JDM? What can I do to fix it?

Edit: Here's what I've done (that hasn't fixed the problem):
New Air Filter
New Cap & Rotor
New Fuel Filter
New Spark Plugs
New Wires
Ran a bottle of Lucas Injector Cleaner
The car isn't burning or losing oil...

ECU should be the same as before the swap.
Fuel injection system was transplanted from the old engine to the new, so that's the same too.

Help???

instructor74

what engine did you install? Are you running the correct ecu for the engine.

melitza03

The old and new engines should be equivalent... both D15B7's. So the ECU should be correct.

melitza03

I did find out that the JDM engine was carburated, vs the one that was replaced was fuel injected... So they moved all my parts over from the fuel injection engine onto the JDM engine so that it'd still be fuel injection.

But that mileage isn't great - so is there something else that needs to be changed to get that efficiency back up?

I've browsed the forums and found the following checklist for crappy gas mileage:
replaced: spark plugs, wires, air filter, cap & rotor, fuel filter
not addressed: TPS, map, O2 sensors, PCV valve, IAVC, fast idle valve, t-stat, cat, distributor ECU (same)

But I'm not sure where to go from here...

melitza03

Bump. Any ideas?

TomO

Do a compression test with the engine up to operating temp and the throttle wide open. Then post the results here.

Some JDM motors may have fewer miles on them but are beaten to hell and not taken care of since the owner knows the engine will be gone soon.

melitza03

Knowing what I know now, I would have had the head repaired on the old engine, that's for damn skippy.

Is a compression test something I can get done for cheap by someone, or should I go out and buy a compression tester myself?