Car lacks power

I have a 02 nissan sentra gxe with 100k miles. I got it used when it had 70k miles on it. It is very reliable and gives me great milage. However I noticed when I drive uphill the car lacks power and is unable to pick up speed. If I drive too long uphill at high speed the engine starts getting hot and I am forced to slow down.

I am a Automotive Technology student at a Community college and would like to diagnose this problem myself.

I changed the spark plugs recently and that did not slove the problem. I was suspecting it might be the fuel filter. However on a 02 nissan sentra it is in the gas tank and is not replacable.

It can also be the oxygen sensor. However I thought the car engine lights will indicate when it is time to replace the oxygen sensor.

Does any one have any suggestions ? Thanking you in advance.

The engine should not overheat going up a hill, even for a long time. How are the fluid levels (Oil, coolant, transmission fluid, etc)? Are there any trouble codes in the computer?

Could be blockage in the exhaust. (Clogged converter or collapsed muffler.)

Is it possibly a plugged or partially clogged cat? If you had a tester you could drill a hold pre cat and check the pressure. It should be no more than 3psi?. Just fill the hole with a screw.

Another thing, what about restricted air filter. Remove the air filter (only for this test) and try it.

If not that, maybe a fuel problem? Put a gauge on it that you can read from the drivers seat if posible. Drive it up the hill and see if the fuel pressure drops? Check for the fuel pressure spec’s. It should be near the specs all the time. Sitting idle, as well as under high demand.

Definitely don’t take your car somewhere and pay someone else to diagnosis it when you can get your solution right here. It’s just a matter of elimination. It you don’t find your solution on this forum, you might try one of the other auto forums out there. I completed an auto tec degree here in UT and refused to take my car to someone one when I know I was just as capable as they were. The only difference is the shop might figure out the solution faster than you, but if you have time, you will eventually get to the problem because there are truely a lot of knowledge folks out here, as well as some idiots, so it’s just up to you to sort through the BS and the real helpful info. Good Luck.

I’m having the same problem with my Nissan pickup. My advice is have the fuel pressure tested. I just checked mine and it’s 6.5 PSI under spec. And the reason the engine begins to overheat when this occurs is because the engine leans out because of the weak fuel pump.


Automatic or manual transmission? Are you trying to drive a manual tranny up steep hills in top gear? An automatic will downshift, but a manual won’t.

Its an automatic transmission.

Are you SURE there is no filter between the tank and the injector rail? The “sock” in the tank is usually not fine enough to protect the injectors…Then perhaps an EGR valve that stays open under full throttle (it should close) or as others mentioned a restricted exhaust. But as Tester suggested, check your fuel pressure at the injector rail first…