My '99 4.2 has about 95,000 miles. Over the last 3,000 miles, my power and mileage have declined dramatically. The truck is running like a DOG and getting about 14 mpg mostly city (used to get over 16 under the same driving conditions).

Replaced fuel filter - made no difference. The plugs were replaced at 60,000 miles and still look good. The motor runs WEAK with or without my Superchip installed.

I am going to replace the O2 sensors in an attempt to make it run like it used to.

Any particular brand of 02 sensor that is better than the others? What price have you guys paid? Are you ordering online or getting from an Auto Parts Store? Who has the best prices and service? Is this an easy do it yourself job?

Thanks for any help.

 

Dave,you can get them at Auto Zone or Advance auto,Bosch brand,for 49.00 a piece.You only need the front two.They are the ones that tell the PCM what to do.The rear ones are only for letting the PCM know the catalytic converters are there.You can either buy the special socket for them or use a wrench.Going thru the wheel wells is the easiest way to replace them.Just run your engine to operating temperature,turn off the engine,disconnect the negative battery cable,and replace them.Its that easy! Let us know if it helps bring your mileage back up and your engine pep back.

 

That was exactly the info I was hoping for.

Thanks a bunch, BOF.

 

Put the new front 02 sensors yesterday, 93,500 miles. Took about 40 minutes total including clean up. Went throught the fender well on the driver's side but did the passenger side from the top. Bought the special $6.00 socket when I got the sensors.

Due to short wires/no slack on the driver's side of the harness and slighlty shorter wires on the Bosch sensor vs OEM (probably about 1" shorter), the trickiest part was securely connecting the new left side sensor into the harness. All done 'blind' by feel behind the top of the motor.

Short trip of about 10 miles shows some of the pep has been restored. Requires noticeably less throttle to keep up with traffic, so hopefully mileage has improved.

Superchip is still disconntected as I've got regular in the tank. With the bad 02 sensors, the truck was weak (no difference) with or without the chip.