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Hello from snow country Idaho,
Sorry to interrupt - still figuring this site. Posted on new member area, but not sure that is where I need to be.
Just purchased an '87 sentra (carburetor, automatic), for a short commuter, not exactly what I wanted but, got sucked in by need and promises of great gas mileage. The problem is that the gas mileage is terrible! Barely 20mpg. I tuned the car up immediately (except for the pcv valve, can't get to it yet) but to no avail.
I know I need a muffler (and perhaps catalytic converter?) but could that warp my mileage so much? My quandry, is what should I have a "qualified" mechanic tackle first - the exhaust system or have a look at the carburetor? (can't do both yet) There are 122,000 miles on it. No history but extremely clean. It runs fine aside from the gas mileage and the quirky start ups - great cold starts, but I must hold gas pedal to floor for a rough start after it is warm. It barely catches.
Also there seems to be a lot of carbon build up on muffler and old plugs. Any help?

 
 

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Maybe try a topside engine cleaner like seafoam?

To clean carbon out of the chamber and valves:
Years ago we used to use a soda bottle filled w/ H2O and let the engine slowly suck in the water through a vac line w/ a special ' restrictor' in the line, rate of about 5 min per bottle. The restrictor we used was the end of a ball point pen...

Don't forget your mileage might also be down because of the 'special winter blends'.
 

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GA16DE
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Mechanical carb?
Easy to service
Electronic assisted carb? It comes with an optical distributor
Hopeless...
Replace it with a mechanical one, the distributor too Look for a centrifugal advance unit
 

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minute rice sentra said:
Try changing the oxygen sensor and there's no hope for carb as far I'm concerned, I know nothing about the carbed sentras.
i'll second o2 sensor. when i changed it on my pulsar i jumped up to a steady 34.5 mpg.....no matter how hard or unhard to push it
 
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