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Discussion Starter · #1 ·
Every now and then once my 2004 Xterra Supercharged is warmed up, it feels like it goes into a limp mode but there is no CEL. For instance, when I take off from a light, it feels like the transmission is starting out in 2nd, and it hesitates to rev. Even while cruising, if I step on it to down-shift, the engine will rev to around 4k RPM and barely pull itself with a very subtle surging acceleration. I had the codes read at AutoZone, and the guy told me that there were no saved codes.

I figured that the slight surging at higher RPM, and general loss of power was a slight misfire, so I changed all the spark plugs, wires, dist. cap, and rotor yesterday. The cap and rotor looked like they had never been changed.

After everything was finished the truck ran great and pulled much better. However, after driving it around for awhile, it began acting like it was in some limp mode again, and this time the CEL started flashing for a moment and then went out again.

I guess I'm unsure of where to go from here. I'm going to get the codes read again today. The only other thing I did yesterday was disconnect the battery while I was working on it(to reset the ECU), I cleaned the MAF, and cleaned the K&N which was filthy. Any help would be greatly appreciated.

Thanks.
 

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Discussion Starter · #4 ·
No I didn't look down at the bearing, but I did push the shaft back and forth to feel for any play. I don't know if that's enough to check it, but it felt pretty solid
 

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Knock sensor is my guess. Does not turn on the CEL and puts the supercharger into bypass mode.
 

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Discussion Starter · #6 ·
Knock sensor is my guess. Does not turn on the CEL and puts the supercharger into bypass mode.
Would there be a saved code if it didn't illuminate the CEL? I read somewhere that the knock sensor can be over sensitive and pull timing even when there isn't any knock. I was unaware that it drops all boost too, but that does explain the lack of power.

I may try that resistor mod for the knock sensor. I always run premium, however I kind of doubt the last owner ever did.
 

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Discussion Starter · #7 · (Edited)
Just went and had the codes read again. No codes and nothing saved. Looks like I'll be chasing a ghost

I guess on a side note, the passenger side exhaust manifold has a pretty decent leak. It has some Pacesetter(I think) headers with the cats welded onto them. I'm hoping they are just cracked in a convenient location so I can weld them because removing the header looks like a complete PITA
 

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Just went and had the codes read again. No codes and nothing saved. Looks like I'll be chasing a ghost

I guess on a side note, the passenger side exhaust manifold has a pretty decent leak. It has some Pacesetter(I think) headers with the cats welded onto them. I'm hoping they are just cracked in a convenient location so I can weld them because removing the header looks like a complete PITA
Sounds electrical to me. When I say electrical, I mean you have a bad contact somewhere.
Clean up electrical harness connections with contact cleaner and put a dab of dielectric grease on them.
Or, do what many people do and throw new parts into the mix.

I doubt your exhaust is the issue. That would throw O2 sensor codes.
 
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