Questions and Answers

Nissan 240-SX Running Rich Q. Hi Vince, I have a 1990 Nissan 240-SX and the car has been running rich for a long time, I've changed fuel injectors and electrical connectors for fuel injectors and O2 sensor and lastly the fuel filter. When I changed my O2 sensor it was coated black. I am getting 14 mpg and its hurting my wallet.

What could cause the car to run rich and the idle to fluctuate? The car runs good besides the problems noted but I need to improve the gas mileage or get a gas saving car.

Thanks a lot!

A. Yes, it does indeed sound like it is running rich. What you need to do is hook up a fuel pressure tester and see what the fuel pressure is. If the fuel pressure regulator is bad it can cause the fuel pressure to be too high and cause the engine to run rich.

I would also see if any codes are stored in the computer that will give us any hints of other possible problems.