Why is my 1993 Nissan Sentra getting poor fuel economy?

Question

My car has 123,000 miles on it.

I have a 1.6L engine with a 4-speed automatic with overdrive.

With the A/C off, it gets 24MPG; with the A/C on, it slumps down to 18-21MPG.

I have replaced my air filter and spark plugs; my fuel filter appeared to be okay.

My car is really slow. I have utility vans and buses pass me while I'm accelerating from a stop. It's not so bad without the A/C, but even then the acceleration isn't very good.

My engine is supposedly rated for 110HP, but it isn't putting out nearly as much; my girlfriend's Ford Probe has 110HP and it out paces my car without even trying. If you floor it, it downshifts and revs really loud but still hardly goes anywhere.

The engine sounds fine and doesn't sputter or anything. My parents' are getting 27MPG from their 2.4L '96 Altima and 27MPG from their 2.0L '90 Camry while I'm getting 18-21MPG from a 1.6L engine, the smallest of all of these.

Here are some more details.

For the person suggesting the thermostat is bad, my radiator has a crack in it and leaks constantly while the car is on. The car does not overheat.

I have checked the tranny fluid and it's at the proper level and has no blackening.

I have tried fuel injector cleaner with no results.

I bought a K&N air filter. It helped a little, but not much.

I changed my spark plugs and three were beige in color, indicating normal fuel mixture. The first spark plug was white (indicating lean mixture) and had oil leaking into where it screwed in.

I've had all my belts replaced and none of them were for timing. I have a dual overhead cam, so I don't believe I have a timing belt anywhere...

Perhaps it is a plug in the catalytic converter?

Answer 1

Has the timing belt been replaced?It should be, one at every 60,000 miles.

Check for a clogged exhaust system, it can cause the lack of acceleration.

running the AC on older cars will rob gas mileage and horsepower.

New cars are more accurate in gas consumption due to advances in computers and sensor manufacturing.You have to expect that the older the car the worse the gas mileage.

Also, remember that engine displacement is equal to horsepower and acceleration.( the smaller the engine the weaker the power)

Answer 2

1993 nissan sentra poor fuel economy

Answer 3

Here's one that most folks don't think of:

The thermostat will eventually fail and stay in the open position. When this occurs the coolant continuously circulates through the radiator and the engine may never reach operating temperature and the car will be running in an open loop meaning the brain box or engine management computer never takes over the adjustments of fuel air mix and or timing.

The only other thing that might be going bad is your catalytic convertor. When they plug up you have way too much back pressure on the engine and lose power and MPG's.

Good Luck!

Answer 4

RE:
Why is my 1993 Nissan Sentra getting poor fuel economy?
My car has 123,000 miles on it.

I have a 1.6L engine with a 4-speed automatic with overdrive.

With the A/C off, it gets 24MPG; with the A/C on, it slumps down to 18-21MPG.

I have replaced my air filter and spark plugs; my fuel filter appeared to be okay.

My car is really slow. I have...

Answer 5

put a bottle of concentrated fuel injector cleaner in the tank. nothing from STP, that's not a very good brand.

with the a/c on, you will lose mileage, as the engine is having to huff & puff more, but that's a significant drop, but you do have over 100,000 miles, the engine could be wearing down on you. just because its an import means nothing.
Do a compression test next time you swap plugs. and use NGK or Denso plugs.

Answer 6

Try a new distributor cap and rotor first, then the thermostat(I had a car run 10 better after replacing the thermostat once). Then move to the pricer ideas above.

Answer 7

Sounds like the transmission is slipping to me, have you looked at the fluid level lately?