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SHOULD I REPLACE MY KNOCK SENSOR? WOULD THAT STOP MY CAR FROM CHUGGING? PLEASE HELP!!!

  • Tiny
  • honeydarling
  • 2004 Nissan Xterra
  • 89,000 miles

My xterra has been chugging- it is an intermittent problem and occurs once a week, but is dangerous to drive on the freeway especially when it does chug. It acts like it is out of gas. The car has been checked for fuel line problems, a new fuel filter was put in and the fuel pump was said to be fine. We put in a new MAF sensor, new spark plugs, new distributor cap and rotor and oil change. I just got it back from yet another mechanics diagnosis and now they say it needs a new knock sensor. I had taken it to Nissan where they said a knock sensor would not cause chugging. Should I replace the knock sensor to the tune of $600 or does anyone have any other suggestions? The mechanic said my knock sensor is sending a signal to the computer causing it to malfunction. I have no idea about cars- does this make sense? I told him how Nissan dealers told me the knock sensor wouldn't be causing this issue. Nissan could not find the problem causing the chugging since there was no check engine light going on at the time.

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Friday, May 25th, 2012 AT 7:22 PM

6 Replies

  • Tiny
  • Docfixit
  • Expert
  • 18,993 posts

Agree with Nissan knock sensor will not cause "chuging". So Dealer checked out and found no problem? Intermittent very dificult to solve

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Friday, May 25th, 2012 AT 8:46 PM
  • Tiny
  • djcl
  • Expert
  • 786 posts

Every nissan xterra has that code stored in it. It shouldnt turn on the engine light. And will not make it run poor.

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Friday, May 25th, 2012 AT 8:58 PM
  • Tiny
  • honeydarling
  • Member

Oh thank you so much for your replies. I was very worried about making the decision to go ahead and put in a knock sensor. When I took it in to the dealer the first time, they said it may be a crank position sensor but since they could not get the car to chug on them that they could not guarantee me anything. That crank position sensor would be $970 for them to fix it and that's a gamble with money I just don't have right now. It's been about 6 months and over 5 different mechanics who have no clue except to say its the knock sensor, speed sensor or crank position sensor. We changed the speed sensor twice one with aftermarket one and one with OEM part the second time. If anyone has any other ideas please advise. This is the car I need to get to work with and now I can't even drive it. Just to mention. The car never stalls out completely, just chugs and I put it in neutral and then drive and it works fine for 20 more miles or so and then does the same thing all over again. I asked the mechanic if it could be my transmission going out. He said no the engine was running fine. Does that answer make sense? I wish I knew more, but I don't have anyone here to ask.

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Friday, May 25th, 2012 AT 9:16 PM
  • Tiny
  • nalasnike
  • Member

Honeydarling, I just went thru the same thing with my 2002. Seems the
initial problem was the Mass Airflow Sensor. The part costs about $150. Be careful though, mechanics that installed mine charged $350 just for the part and you could probably replace it yourself in less than an hour.

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Tuesday, June 12th, 2012 AT 2:29 PM
  • Tiny
  • wguru
  • Member

If your engine is actually knocking and at the same time the KS is also malfunctioning (usually caused by a wiring connection that's loose or corroded), the ECM doesn't then wouldn't/doesn't know of the knock and systems will not compensate for this, so replacing or fixing the knock or its wiring (moreover knowing for sure the KS is functioning properly) is essential to avoiding damage and wasting gas.

Installing a new KS shouldn't help with your issue of focus, so long as you're certain your KS is working fine. FYI - Don't let any mechanic try and tell you a KS cannot be tested in-place on the vehicle (w-key "on", assure 2.5V to 5V is supplied to the KS's core wire, that and assure good ground resistance is measured between the other wire and the engine block).

My knock sensor went bad on my '97 Pathfinder and rather than tear the engine apart (ref. Your $600, my $900) to replace the old KS, I opted to spend about $50 total for a new KS and stub harness which I spliced onto my existing harness and simply bolted the new KS onto the manifold (I left in place the now abandoned KS and it's portion of unused wiring).

My engine runs smoother, has more power and improved mpg.

Serious Note - w/today's adulterated gasolines, ie; carbon buildup results on valves and piston heads, the latter carbon deposit frequently causes the ignited spark to bounce off the piston head at the same time as cylinder fires and instead of a single explosion in the cylinder. Two smaller ones occur, that is until someone runs some good fuel/injector cleaner through the system (assuring that a tank of "premium" gas is run with the cleaner) and when done, often significantly improves power and smoother idling.

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Friday, July 20th, 2012 AT 2:52 AM
  • Tiny
  • wguru
  • Member

I omitted mentioning that that my old KS had been indicating engine 'knock' ("#4 cylinder misfire") and yet myself and others found absolutely no evidence that might substantiate indication of knock on that cylinder (its fuel injector being the only other viable possibility for possible misfiring, that or a bad knock sensor.

All I know is my old KS seemed to falsely indicate engine knock and the supposed misfire trouble code disappeared only after I replaced my bad KS.

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Friday, July 20th, 2012 AT 3:16 AM

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