Knock Sensor Bad On 1999 Fourrunner?

I Am Getting An Error Code That The Knock Sensor Is The Reason Why My Check Engine Light Is On. I Have The Four Cyl. Engine. I Just Changed The Fuel Filter And The Light Came On. It Does Not Ahve The Power That It Had Before. Gas Milage Is All Over The Place (inconsistant). The Engine Seems Like It Is Skipping Between 40 And 65 Miles Per Hour???
If This Is The Problem, Is It HARD To Change On This Engine?
Thanks For The Feedback.

The knock sensor is on the driver's side of the engine next to the front of the #3 cylinder, near the top of the block. If you can get to it to remove the sensor wire and get a socket or wrench on it, you can get it off easily. Torque the knock sensor to 27 ft-lbs.

If you have to remove the intake manifold to gain access, it will be a more difficult job, but not too bad. You can loosen the intake manifold from the head and slide it to the side without doing much more than getting what is needed for bolt-access out of the way.

Clean the gasket surfaces for both manifold and block of anything down to clean metal with laquer thinner and a brush - without damaging the surface in any way. Use a new gasket for the intake manifold-head surface and torque everything down correctly (22 ft-lbs in three equal steps, the center bolt first working outward - Each bolt tightened to each torque step before tightening them all to the next torque step. Lubricate all the bolts with a drop of engine oil).

I would see if you can see it without taking anything apart. Getting a wrench on it would be 90% of the battle. Of course it must have clearance necessary to back it out of the bolt hole without interference.

I was looking at it this weekend. It appears now that I have knocked the wire out of the clip harness
that goes on the sensor when I put on the fuel filter. It is so hard to get at. BOTH. My fourrunner runs, but their is hesitation. It seems to lack power. This has to be causing it, right? What will happen if I drive the vehicle with the knock sensor diconnected like this? Thanks for the feedback above also...

I would guess that the default condition is retarded or inconsistent ignition timing. It seems a fairly easy job. If you don't feel confident, take it to a mechanic you trust and get it fixed. Can't cost more than an hour of labor.

If the problem is inconsistant wait until it starts running good and then disconnect the knock sensor. If it starts running bad then you found the problem.

I had a similar problem on my 86 Volvo 740 Turbo. I ran 87 octane in it for several months and finally the knock sensor broke. It had no power below 4500rpm because the timing was so retarded. It was an intermittant problem. They didn't have check codes back then so I had to throw the diagnostic book out the window and just unplug stuff until I could duplicate the problem.

What octane fuel are you running? What does the owners manual recommend? I am planning on getting a 4cyl 4runner so I would like to know if the manual asks for more than 87 octane.

Thanks for the info. because that is what is happening.
The 4 cyl. fourrunner is recommended 87 octane.
The problem was that I pulled the wire out of the knock sensor so that it is totally disconected. It is acting like you have stated. I did it chaging the fuel filter. It i svery tough to get at unless you take the intake manifold off.