90 Civic DX fuel question (noob/newb)
 

Hello,

1990 Honda Civic DX (1.5L w/ JDM 4-speed auto with O/D)

My question concerns poor fuel economy. Since my mechanic (reputable Honda/Acura specialist) recently installed a new Matsu****a A/C compressor and assembly, along with a used JDM trans, I have noticed horrible mileage. Prior to the new A/C unit and trans, I was averaging 36mpg combined city/highway driving.

Now, I know the A/C makes the engine work a little harder (requires additional RPM, after which engine needs to rev higher to maintain same speed), but I now only average 20mpg, and it's killing me. However, driving in the heat with the windows down causes extra drag, so it only makes sense that the wind resistance with the windows down would be somewhat similar to using the A/C with the windows up.

The A/C unit should not be causing such a HUGE drop (over 44%). I would say losing 2-3mpg's max would be acceptable, since I drive on the conservative side. I usually have no need to go beyond 60mph.

If you need any additional info, I posted a link in the Transmission section, which outlined (in gross detail) the issues I am having with the very speedy JDM transmission -- could be related somehow.

https://www.hondacivicforum.com/m_221940/tm.htm

Other than that, I am guessing that perhaps there could be:

1. too much freon (R134a) in the system?
2. a bad fuel filter? (never had a prob before)
3. a bad EGR valve?
4. a need to adjust the gearing ratios?

Any kind of help would be greatly appreciated. Thank you!!

-=K=-