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Knock sensor replacement HELP!

Tiny
PATTONVW
  • MEMBER
  • 1996 VOLKSWAGEN PASSAT
  • 172,000 MILES
1996 VW passat 2.0 4/cyl
code was to replace knock sensor. I did this. Now car will not crank up as was before knock sensor replacement. If I crank for a while, it eventually starts with a bit of sputtering. Idles fine, but if I engage gas, it stalls. Check engine light is still on, I do not have a way to check codes. Any help greatly appreciated.
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Monday, July 2nd, 2012 AT 1:17 PM

12 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Trouble code does not tell you to replace sensors. They only indicate a problem with the circuit and it can be the sensor, wiring or even a bad PCM.

You need to check the trouble codes for the MIL indicating. We cannot be guessing what is wrong.

Most parts stores provides free scanning services. Try Autozone.
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Monday, July 2nd, 2012 AT 5:04 PM
Tiny
PATTONVW
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  • 7 POSTS
I did notice gas leaking after cranking the engine over and over around where the fuel filter is. If the fuel filter was clogged, would this cause a possible knock sensor failure?
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Monday, July 2nd, 2012 AT 6:06 PM
Tiny
KHLOW2008
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No. Knock sensors usually fails due to overheating and not gas leakages.

If gas is leaking, it would cause non starting as the fuel pressure would be lower than it should be.
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Monday, July 2nd, 2012 AT 6:13 PM
Tiny
PATTONVW
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  • 7 POSTS
Thanks for the responses, your help is much appreciated!
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Monday, July 2nd, 2012 AT 6:27 PM
Tiny
PATTONVW
  • MEMBER
  • 7 POSTS
OK, I went ahead and replaced the fuel filter. No leaks! I cranked and cranked, finally got it started. It idles fine, drove around for 20 minutes. Sitting still or trying to take off, when I give it gas it seems to want to stall. Sitting at idle if I engage the gas, it will stall and cut off. I cut it off and it it's hard to start, but it does start. All fuses appear to be ok. So what now? I am scared to cut it off at autozone to have a code scan done because I don't want to be stuck there, thus the reason why I am questioning here for tips. Thanks!
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Tuesday, July 3rd, 2012 AT 2:49 PM
Tiny
KHLOW2008
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The trouble code is the key to what could be wrong and without knowing what is causing it, how are we going to help you?

We do not do guess work and if you do not want to follow suggestions, there is nothing much we can do for you.
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Tuesday, July 3rd, 2012 AT 3:02 PM
Tiny
PATTONVW
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  • 7 POSTS
I understand. I will try and do this tonight. Thanks.
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Tuesday, July 3rd, 2012 AT 3:22 PM
Tiny
PATTONVW
  • MEMBER
  • 7 POSTS
OK, went to Autozone, here's the codes:
P0302
P0304
P0300
P0327

Now what?
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Wednesday, July 4th, 2012 AT 1:12 AM
Tiny
KHLOW2008
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P0300, P0302 and P0304 are all misfiring codes. Check the spark plug. Check ignition coil and its wire connectors and sprk plug wires.

For P0327, it is the nock sensor. Did you erase the trouble code after replacing the knock sensor? If not, it could be there because of history and not because the fault is still there.
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Wednesday, July 4th, 2012 AT 4:20 PM
Tiny
PATTONVW
  • MEMBER
  • 7 POSTS
I have replaced the fuel filter, knock sensor and spark plugs. I also cleaned the MAF and checked for vacuum leaks with carb cleaner while car was running. I also took a small water spray bottle and lightly sprayed the coil and wires. I checked the ground wires as well. Autozone won't clear the codes. I unplugged the battery for 2 hours to see if the ECM would clear.
After cleaning the throttle bottle, reassembling everything, the car starts better, but after it gets warm, it starts to misfire again, and after a while it gets worse.
Could I be missing a vacuum leak? Could the engine coolant temperature sensor be failing?
I gained all of this knowledge by searching other forums. Thanks for any helps you can assist me with!
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Wednesday, July 4th, 2012 AT 11:20 PM
Tiny
KHLOW2008
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It could be any of those you mentioned but those are only possibilities. In order to get to the bottom of the problem, you would need to erase the trouble codes and with a scan tool plugged in, monitor the spark plugs etc and get the freeze frame data when problem occurs.

You can also get the freezre frame data that is stied in memory to assist in troubleshooting. These would be recorded since the MIL is indicating.

Code readers would not be able to perform this therefore you would need to get appropriate scan tool.
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Thursday, July 5th, 2012 AT 1:07 PM
Tiny
VWSCOTT
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  • 66 POSTS
Im not at the vehicle, but I wonder about the tbelt. If it hasn't been done and is worn it could very well be slightly out of time causing the knock sensor to activate. I have never seen a knock sensor fail. I think it's telling you of a condition. This can explain hard starts. BUT it's only reporting 3 misfires. Do all of your maintenance then see what happens. Cap, rotor, wires. You have to get everything to manufacturer's standards first. Should be in the owner's manual.
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Saturday, July 7th, 2012 AT 2:18 AM

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