I have a 1990 honda accord coupe it has 275,000 its automatic the engine it's regular stock engine live in AZ. I been noticing that the vehicle is wasting a 1/4 gas just driving 10 mile back and forth from work. The Only change was that air tube broke and had to replace it for aftermarket cold intake because it's hard to find the oem tube and Replace idle air control valve. When it idle it stays at one 1,000 rpm and when it's in drive it goes on 800 to 700 rpm. Scotty any advice what it can be.
Find an older mechanic who used to work on these kind of cars. (After all, how much can one expect from a 30 year old technician who was trained on far more recent cars). Get a compression test (wet and dry).
I would also suspect, given what've you said, that the (presumably) aftermarket idle control valve isn't very good. Have that idle control valve tested.
Also, I'd suggest going to this Forum, which is focused on 1990-2002 Accords. Look through their posts. Ask them these questions, as well. After all, they have collective experience with these particular cars. https://honda-tech.com/forums/honda-accord-1990-2002-2/
Good luck.
