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1999 2.5 rs coupe silver
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Discussion Starter #1 (Edited)
please help .... trouble with the knock sensor

can anyone tell me where the knock sensor is on a 99 rs? also... people that experienced the CEL problem after putting the headers in... the timing is all screwed up on it and it seems like i got 90 hp. i was told not to buy another knock sensor bc the header would do the same thing and cause vibrations to throw the timing off....

if anyone has moved the knock sensor... where the hell can i put it where it wont mess anything up?
so just let me know where it is and where i can move it... thanks.
 

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04 Outback H6 aka old man car
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1st off, the knock sensor is located at the top of the block, underneath the airbox/throttle body.

Did you put headers on?

Did you make sure you reset your ECU after you put your headers on?

Did you get a CEL if so what code is it?

If the sensor itself is busted, the ECU won't advance timing cause it doesn't have anything to measure knock, so it runs crappy to save your engine.
 

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jlaz07 said:
also... people that experienced the CEL problem after putting the headers in...
CEL's from headers are related to cat inefficiencies, not knock sensors.

i was told not to buy another knock sensor bc the header would do the same thing and cause vibrations to throw the timing off....
You were told wrong.

if anyone has moved the knock sensor... where the hell can i put it where it wont mess anything up?
Leave it where it is, that's not your problem.

Answer these questions:

1. Do you have a CEL on?

2. Did you have it scanned to see what it was?

3. What is the code?

Without scanning for the code and knowing exactly what the code is, we cannot help you.
 

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1999 2.5 rs coupe silver
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Discussion Starter #4
yeah the CEL is on, i just went back and got it scanned. it said:

Fuel Trim Malfunction (bank 1)

any ideas?
 

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1999 2.5 rs coupe silver
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Discussion Starter #6
the car is a 99... and yeah that was the code. i guess a lot of ppl are having this problem. i read the thread and ill see where that takes me.
 

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jlaz07 said:
yeah the CEL is on, i just went back and got it scanned. it said:

Fuel Trim Malfunction (bank 1)

any ideas?
If it's fuel trim malfunction it could be either your rear O2 tripping the code because the front O2 is reading incorrectly, or the rear O2 is just reading incorrectly. The rear O2 does affect long term fuel trims and is likely the culprit. However...

Did you reset your ECU after installing your headers? If not, do this first before messing with any sensors... You must follow these instructions TO THE LETTER.

1. Disconnect battery

2. Pump brakes for 60 seconds.

3. Reconnect battery

4. Start Car. DO NOT TOUCH THE GAS.

5. Idle the car for 10 minutes MINIMUM. DO NOT TOUCH THE GAS DURING THIS TIME.

6. Take the car for a drive and see if the CEL comes back.

If the CEL comes back, it's a real sensor malfunction, most likely the rear O2.
 

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1999 2.5 rs coupe silver
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Discussion Starter #8
ok so i reset ecu. CEL came back on. so i just said screw it, i bought both front and rear o2 sensors. even had a shop install them. he ended up erasing the code.
...now since theyre in, it feels a little better but it still feels like the timing is off at times.
its been maybe 5 days since the new sensors were installed and the CEL has not come back on yet.

any other suggestions? my patience is running out and bringing it to a subaru dealer is my last resort. but from what it looks like, i might have to.
 

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sold it to Susie the Subie
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how about taking off those headers and putting your stock ones back on. Sounds like these new ones are the root of your problem. What's the point of headers if you don't have the rest of the exhaust to go with them anyways
 

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I'm assuming that you installed the Borla-Replica headers, in which case that's why it feels rough around the edges. Without the catback, you'll FEEL the pulsation more than hear it, making it feel like the car has a miss or the timing is off.

The only problem is in your head. Put a catback on and you'll understand what I'm talking about.
 

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1999 2.5 rs coupe silver
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Discussion Starter #11 (Edited)
CEL just came back on. and there is a catback on there. which is why i dont get it either.

i think im gonna have to get someone to look at this
 

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Vegas is officially refusing odds on code P0420.

In the event it is P0420, feel free to start a new thread asking about O2 spacers and MIL Eliminators. We haven't had one of those in almost a week.
 
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