I own a 1995 Nissan Quest with approx 91k miles. Prior to my scheduled timing belt replacement, the gas mileage was slowly becoming worse. Now, after the timing belt change, the gas mileage has become atroscious. I’m getting 10-11 mpg at best. Any advice would be most aprpeciated. I have had the vehicle in several times to check sensors, timing, etc.
If the gas mileage drop is legitimately that bad after the change then I would suspect:
A. The cam(s) are a tooth or two off.
B. The distributor ignition timing is not correct.
You state the timing was checked but was it done correctly? Most vehicles with computer controlled timing and fitted with distributors generally have a test plug somewhere. This means it must be grounded, jumped, etc. Failure to do so will cause the timing to be off quite a bit.
I agree with ok4450. It sure sounds like the distributor timing is off, in which case it should either run on when you turn the key off or it should be making a clacking sound while climbing hills. I vote for an advanced distributor since a retarted distributor should actually improve your gas mileage.
Try having the ignition timed and see if it can be corrected by adjustment or if it is out of range.
Change the thermostat if over 5 y.o.
Hi Everyone, thank you very much for the help. I am printing this out to take to the shop. Yes, the thermostat was changed. No, it does not keep running after turning it off. Have not noticed the clicking noises. Unaware of a test plug, but will specifically ask about that.
The other thing to consider replacing would be the Oxygen sensors.
Since your fuel mileage was steadily getting worse before the timing change, it was probably caused by a lazy O2 sensor.
You might want to invest in their replacement, too.
BC.