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2002 XTerra SE/SC, mods to come... to poor
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Discussion Starter · #1 ·
Hey all, picked up a 2002 Xterra SE/SC about two weeks ago, decided to tune it up myself, cleaned the MAF with MAF cleaner, cleaned the Throttle Body with TB Cleaner, changed the spark plugs, ran some injector cleaner through the tank.
First problem was a misfire, sorted that out with fully seating the plugs, rookie mistake, lesson learned.
But now it will randomly take a long time to start when it’s cold, but sometimes it’s fine. Idles at 2000 RPM, RPM bounces from 800-2000, acceleration is sluggish, have a SES light, haven’t checked the code yet, when I did check the code for the misfire I also got the infamous knock sensor code.
Not to sure where to start, any input would be much appreciated.
Cheers.
 

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2002 XTerra SE/SC, mods to come... to poor
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20 Posts
Discussion Starter · #2 ·
Hey all, picked up a 2002 Xterra SE/SC about two weeks ago, decided to tune it up myself, cleaned the MAF with MAF cleaner, cleaned the Throttle Body with TB Cleaner, changed the spark plugs, ran some injector cleaner through the tank.
First problem was a misfire, sorted that out with fully seating the plugs, rookie mistake, lesson learned.
But now it will randomly take a long time to start when it’s cold, but sometimes it’s fine. Idles at 2000 RPM, RPM bounces from 800-2000, acceleration is sluggish, have a SES light, haven’t checked the code yet, when I did check the code for the misfire I also got the infamous knock sensor code.
Not to sure where to start, any input would be much appreciated.
Cheers.
Also, once the engine is warmed up it’s completely normal idle, but bounces around occasionally yo to 1200
 

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2001 se 4x4 5spd 32"
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With having the super charger you do need a working knock sensor.

The SES light and code may be the answer to what ever is making the idle jump around.
 

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2002 XTerra SE/SC, mods to come... to poor
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Discussion Starter · #4 ·
Got the codes diagnosed today, PO123, throttle position sensor, must have something to do with when I took the throttle body off to clean it, also has the knock sensor code (ugh it’s hiding under the supercharger and intake manifolds)
And some o2 sensors but those can wait, so bizzare, idles at 2100 as of now, but once it warms up it’s a okay. Also the power band seems to not be so choppy.
 

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That knock sensor might be going off because the TPS is doing weird stuff causing misses. TPS are pretty cheap, just a bit of a pain to adjust right. Start there, clear the knock code, and see if it stays gone. If so, great, if not, then DEFINTELY do a relocate. The factory one takes a LOT of work to get to, and basically all it does is retard your timing if you start getting detonations or misses, which you should be able to feel by the change in how the engine runs and idles.
 

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2002 XTerra SE/SC, mods to come... to poor
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Discussion Starter · #6 ·
That knock sensor might be going off because the TPS is doing weird stuff causing misses. TPS are pretty cheap, just a bit of a pain to adjust right. Start there, clear the knock code, and see if it stays gone. If so, great, if not, then DEFINTELY do a relocate. The factory one takes a LOT of work to get to, and basically all it does is retard your timing if you start getting detonations or misses, which you should be able to feel by the change in how the engine runs and idles.
Thanks for the reply, I’ve ordered plugs wires, rotor and cap, old ones had a lot of corrosion and looked to be needed replaced regardless, if this does not fix it I will go to PicknPull and get a TPS. I’ve heard negative things about relocating the knock sensor with the supercharged engine. I’m a broke high school student and can’t afford premium all the time, and the knock sensor is the only thing saving my engine from kaboom, engine was swapped so I really have no clue how many km or miles it has.... So I want to be able to make sure it’ll last me at least a couple years. Regardless I’m forced to drive it around right now with a misfire because I have no other viable transportation. Why do car parts take so long to arrive :mad:
 

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Agreed, I have also heard not to mess with the factory knock on the SC, I don't recall the details of the explanation, but it made sense to me. Something about them being more sensitive to detonation and needing the KS to work effectively. Go through the service manual procedure for setting the TPS, and that may fix you up. The only other thing besides the distributor, MAF, TPS, that could be a possible issue is maybe the IAC under the manifold, but that is much less likely I should think.
 

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2002 XTerra SE/SC, mods to come... to poor
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Discussion Starter · #8 ·
Agreed, I have also heard not to mess with the factory knock on the SC, I don't recall the details of the explanation, but it made sense to me. Something about them being more sensitive to detonation and needing the KS to work effectively. Go through the service manual procedure for setting the TPS, and that may fix you up. The only other thing besides the distributor, MAF, TPS, that could be a possible issue is maybe the IAC under the manifold, but that is much less likely I should think.
Yeah, I'm really hoping the knock senor hasn't gone bad but if it has I will order the KS and gaskets and take everything off to get to it, what a headache...
 

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2004 Xterra XE 4WD Auto 3.3L NA V6
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Instead of digging down to get the KS, get a new one and relocate it to a location where you can get to it and where it can hear engine noises. You may need/want to find a pigtail to make it easier to wire into the stock harness. Leaving the old one in its stock place and "unplugging" it by cutting the wires so you can add the new one will not damage the engine in any way.

Later, when your OCD just can't take it any more, you can take that miserable excuse of an intake off and pull the KS out. While there, you can service all of the hoses that run through the middle of the engine.
 
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