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Old 03-02-2013, 03:43 AM   #1
POAB
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Default Knock sensor help

So my car had a bad knock sensor and it caused a mild hesitation from time to time with my car. I replaced the knock sensor only for it to have CEL on all the time and heavy hesitation on the engine, worse than before I replaced the sensor.

My buddy and I loosened the knock sensor and the CEL was still on but the car ran beautifully for all of 20 minutes. I get to the auto store, erase the codes and go to get gas and the CEL comes back on and heavy hesitation returned.

Does anyone have any ideas?

Update.

After replacing the PCV and the air-filter the car dropped the P0328 code and the only code on is the P0325. Also the hesitation slightly improved (Mild to heavy hesitation not always heavy)
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Last edited by POAB; 03-03-2013 at 05:45 PM.
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Old 03-02-2013, 08:32 AM   #2
RaceFaceXC
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What tq and angle did you install the new sensor to?
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Old 03-02-2013, 10:50 AM   #3
yarrgh
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Quote:
Originally Posted by RaceFaceXC View Post
What tq and angle did you install the new sensor to?
Troof. Those sensors are very particular to orientation and torque. Also, what were the CEL codes?
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Old 03-02-2013, 11:29 PM   #4
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The angle is correct. We torqued it by hand, but we made sure it was snug so we didn't over torque it.

The codes were P0325 and P0328.

I just replaced the air filter, and PCV valve and it's now only bringing up the P0325 code.
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Old 03-03-2013, 01:43 AM   #5
Dr. Octawakaoctapus
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How did the mating surface on the block look?
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Old 03-03-2013, 03:03 AM   #6
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Quote:
Originally Posted by Dr. Octawakaoctapus View Post
How did the mating surface on the block look?
We cleaned the mating area and the bolt before we installed. So no rust or dirt if that's what you mean.
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Old 03-03-2013, 09:00 AM   #7
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Quote:
Originally Posted by POAB View Post
The angle is correct. We torqued it by hand, but we made sure it was snug so we didn't over torque it.
So you did not use a wrench? What angle is correct?
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Old 03-03-2013, 12:55 PM   #8
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Quote:
Originally Posted by RaceFaceXC View Post
So you did not use a wrench? What angle is correct?
We used a wrench and I just used a torque wrench to make sure.

Last edited by POAB; 03-03-2013 at 01:29 PM.
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Old 03-03-2013, 01:02 PM   #9
yarrgh
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What raceface was getting at is there's 2 types of "right".
1. What you think is right.
2. What is actually right.
The two might jive, but it's entirely possibly that they're not.

Your 2 codes are about the circuit, not the sensor itself. Search on torque values and angle for a better description. 45 degrees from the block centerline, towards the TB. This sensor is grounded to the block, make sure that your grounds are good/clean. Oh, and try not to be a bitch, it's not becoming.
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Old 03-03-2013, 01:31 PM   #10
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Quote:
Originally Posted by yarrgh View Post
What raceface was getting at is there's 2 types of "right".
1. What you think is right.
2. What is actually right.
The two might jive, but it's entirely possibly that they're not.

Your 2 codes are about the circuit, not the sensor itself. Search on torque values and angle for a better description. 45 degrees from the block centerline, towards the TB. This sensor is grounded to the block, make sure that your grounds are good/clean. Oh, and try not to be a bitch, it's not becoming.

hahahahaha
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Old 03-03-2013, 01:34 PM   #11
POAB
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Quote:
Originally Posted by yarrgh View Post
What raceface was getting at is there's 2 types of "right".
1. What you think is right.
2. What is actually right.
The two might jive, but it's entirely possibly that they're not.

Your 2 codes are about the circuit, not the sensor itself. Search on torque values and angle for a better description. 45 degrees from the block centerline, towards the TB. This sensor is grounded to the block, make sure that your grounds are good/clean. Oh, and try not to be a bitch, it's not becoming.
It's exactly how it is in this photo


Like I said earlier, the second code dropped once I replaced the PCV and air filter.

Two days with very little sleep and no cigarettes can bring out my inner bitchiness. I had to edit my post towards raceface because even I felt like I what I said was a bit of a douche thing.
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Old 03-03-2013, 03:53 PM   #12
Dr. Octawakaoctapus
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Whats the year and model?
And its the P0325 right?, earlier you said P0235

Last edited by Dr. Octawakaoctapus; 03-03-2013 at 03:58 PM.
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Old 03-03-2013, 05:43 PM   #13
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Quote:
Originally Posted by Dr. Octawakaoctapus View Post
Whats the year and model?
And its the P0325 right?, earlier you said P0235
99 Impreza. P0325 is correct. CEL typo haha
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Old 03-03-2013, 07:18 PM   #14
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No worries, since the sensor is new we can assume it's not faulty. Now it's time to inspect the circuit. How are the grounds? Try to add a temporary ground and see if anything improves. Clean the existing grounds while you're at it. You can also unplug and clean the main harness plugs. They're brown and white at the passenger rear of the IM.
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Old 03-03-2013, 07:23 PM   #15
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How do I go about creating a temporary ground? I've only assumed the grounds were good. I'll clean and check those.
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Old 03-03-2013, 08:32 PM   #16
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I normally take a sewing needle/paperclip and backprobe the pin that is grounded for the circuit. I then take a wire with two alligator clips and one goes on the pin and the other to the negative terminal of the battery.

hope that helps.
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Old 03-03-2013, 08:45 PM   #17
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Quote:
Originally Posted by scarney1988 View Post
I normally take a sewing needle/paperclip and backprobe the pin that is grounded for the circuit. I then take a wire with two alligator clips and one goes on the pin and the other to the negative terminal of the battery.

hope that helps.
That would help. except that I have none of those items haha
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Old 03-04-2013, 05:57 PM   #18
yarrgh
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There is no pin for the ground on this circuit, it's the block. Find some wire, any wire. Now find a bolt on the block. See that one right by the throttle cables, the one holding the fuel lines in place? use that. Now, find a place on the chassis to ground to. You can use the shock towers if you like, or the existing ground by the dogbone. Attach the other end of the wire here. It doesn't have to be great since it's temporary. Make sure it's ok for a few days of testing, don't get it caught in rotating parts. If you want to add a permanent ground, use ring terminals and zip ties. Search on "big 3" for ideas. it's not difficult.
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Old 03-05-2013, 01:49 AM   #19
POAB
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So update. The knock sensor keeps acting up randomly. Today I went about 4 hours with absolutely no problems, erased the code and the CEL was gone. CEL flips on while I'm stopped at a stop sign, car has a mild hesitation for all of 5 minutes and runs fine and the light turn off. It was like that for about 2 hours. When I return back to my car and turn her on, CEL pops up and hesitates for about 5 minutes again and back to normal.

I cleaned the ground/block when I installed the knock sensor. Weird thing is my car was doing this before I replaced the knock sensor, and when I look at the old sensor it looks fine. Could the problem be somewhere else and should I still check all the grounds?
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