Chasing Low Fuel Efficiency Problem

[Cal Learner]

1990 Maxima, 152K miles, original owner, always serviced, completely stock, gentle driver.

For the past year, fuel economy has been dropping, but only for City driving. I'm now averaging about 15 mpg in town. Highway mileage continues to be about 26+ mpg. Within the past 12 months, new NGK plugs, new coil/ignition wires, new air and fuel filters, new tires inflated 3 psi above factory spec, new thermostat.

Within the past 3 years, all new injectors, new coolant temp and mass air sensors.

At the moment, I don't have a really reliable indy, and I'm not a good enough shade tree mechanic to know what to look at next. What do you experts suggest here? TIA

[maxhopper]

You might try an intake cleaner or running sea foam through the engine. You could have an issue with carbon build up.

[irprobeman]

Everyone always told me seefoam and change out ur o2 sensors. Pretty easy, just get a o2 socket. Autozone.com has location map for most parts on your car.

Hope this helps.