Slight Hesitation after Knock Sensor? - Subaru Outback - Subaru Outback Forums

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Old 02-26-2009, 11:07 AM   #1 (permalink)
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Default Slight Hesitation after Knock Sensor?

So my 1997 Outback Legacy Wagon, 5 speed manual with 118k miles was throwing a knock sensor code, which the dealer changed and cleared the code. They had the agreement with the previous owner, and did it no charge to me.

Prior to that, I drove the car around about 85 miles with the CEL on, and the car drove fine.

After the dealer changed the knock sensor and cleared the CEL I am getting a slight hesitation in the 900-1600rpm range.

It is rather weird, as it doesn't happen all the time. It happens in gear 1, 2, and 3 only.

Basically say I am driving at 45 mph, then coming up to a light, downshift to second, slow down, and release the clutch (THIS IS WHEN IT HAPPENS), if the RPM at this time is in the 900-1600 range, there is a hesitation, shaking of the car (best I can describe it) as it is going forward.

THen it becomes fine.

It also does it, from a stop light, 0mph, in 1st gear, release the clutch, and then it does a bog.

It doesn't do it all the time, but intermittently.

I also thought maybe I wasn't putting enough gas from a stop, but I am. If I rev to 1500rpm, it isn't doing it in 1st gear.

It isn't a big problem, but can be annoying sometimes.

I am doing a full
Fuel FIlter
Air Filter
Oil Filter
Tranny/diff change
Plugs
Wires

In 2 weeks. I am wondering if there is anything I need to look at , or if this is a common problem.

Thanks!
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Old 02-26-2009, 04:10 PM   #2 (permalink)
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How long have you been driving with the new knock sensor? If they cleared out all the old parameters, it could just be that the new sensor hasn't retarded/advanced the timing to it's correct setting yet, and it should do that by itself pretty quickly.
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Old 02-26-2009, 04:11 PM   #3 (permalink)
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Quote:
Originally posted by 07OregonOutback
How long have you been driving with the new knock sensor? If they cleared out all the old parameters, it could just be that the new sensor hasn't retarded/advanced the timing to it's correct setting yet, and it should do that by itself pretty quickly.
181 miles as of this morning.
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Old 02-26-2009, 04:22 PM   #4 (permalink)
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It should have set the parameters by now.. have you checked to see if it is installed correctly? If it is loose or anything it could be setting a false knock and retarding the timing when it doesn't need to.
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Old 02-26-2009, 04:25 PM   #5 (permalink)
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Quote:
Originally posted by 07OregonOutback
It should have set the parameters by now.. have you checked to see if it is installed correctly? If it is loose or anything it could be setting a false knock and retarding the timing when it doesn't need to.
I have no idea what it is and where it is.

A friend is helping me do the plugs/wires, I will ask him to check for me in 2 weeks.
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Old 02-26-2009, 04:34 PM   #6 (permalink)
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I found a thread that might help you.

http://www.subaruoutback.org/forums/...s=&postid=6850

They describe where to find it in there. Not sure how similarly our engines are built since they are 10 years apart, so i'd rather not lead you astray by telling you where it is on mine.
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Old 02-26-2009, 04:50 PM   #7 (permalink)
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The knock sensor is right below the throttle cable cam. It is a black plastic kind of round button with a wire coming off the side and held down with one bolt through the center.
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Old 02-26-2009, 04:57 PM   #8 (permalink)
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On the 97, it should still be on the top of the block... just below the throttle body (driver side).

it should be oriented on an angle from the back of the firewall.
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Old 02-26-2009, 05:00 PM   #9 (permalink)
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Thanks guys. Do you guys recommend I take it off and re install it?
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Old 02-26-2009, 06:10 PM   #10 (permalink)
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Yeah, and make sure the connection between it and the block are clean, as they said in the other thread that is where it grounds. If it has a dirty ground that would cause false readings as well.
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