Hello zdrivers, I have a 1990 300zx Na, automatic and I'm getting horrible gas mileage, I'm talking like 8-9 mpg driving like an old old lady cause I'm going through $100 bucks a week! The car runs great other than a very small hesitation on take off but very small, In the past I've changed the injectors and coils and fuel pump, they were replaced with brand-new Bosch parts, my question is what part or parts could go bad that would cause this horrible gas mileage? Or maybe a tuning is needed? I really don't notice anything wrong with engine when I stomp it it moves strong, any suggestions are appreciated.

 

gas leak? timing

 

Timing belt was done, no gas leaks. I'm thinking tsp or fuel regulator, I just don't know.

 

Have you checked your (catalytic converter) > culprit for that and it's the last thing we think of.A bad trottle valve switch or out of adjustment.

 

No I haven't checked the cats, would that cause bad mileage?

 

yes they would. they also cut back on your gas mileage period. my old truck gets an extra 1-2 mpg with the cat removed. but its illegal. so if its bad just get a performance cat.