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1991 Nissan Sentra- reduced gas mileage- where to check?

the factory rating for my 1.6L 4 speed manual sentra claims 25 city

33 highway. I have always maintained over 30mpg when I check the mileage between fillups. I generally do this using a full tank of gas so as to get a better average. Now my mileage is under 25 and has been as low as 22mpg. I have done a tuneup, installed a new O2 sensor, checked the MAF sensor, but haven't found anything out of the ordinary. I was wodering if I could have leaky injectors, despite the fact that the car runs and idles fine. I have replaced an injector about a year ago because it quit working entirely (kind of obvious when you lose a cylinder's worth of power on a 4 cylinder engine!) but the other 3 are original and have 160k miles on them. Any advice out there for me? This is my daily driver for work (30 miles/day) and I would love to have those mpgs back!
Reply to
robbie
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A few other things I can think of:

Air filter blocked by dirt Tyre (tire) pressure low Spark plugs or plug leads faulty Thermostat over-cooling

A leaky injector might be inclined to cause hard starting (overfueling the engine while stopped as it releases residual fuel-line pressure).

John

Reply to
John Henderson

You can get an idea whether all cylinders are running at approx the same mixture ratio by examining the colour of the deposits on the internal spark plug insulators.

John

Reply to
John Henderson

That is about what I get with my '92 with 180K. My milage went up when I replaced the faulty Coolant Temp Sensor, which was also causing hard starting in cold weather.

I don't think there's any good way to test it, but it was about $25 and was simple to change, I didn't have to drain the coolant.

PB

Reply to
Plague Boy

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