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Loss of power at low RPM

9K views 11 replies 4 participants last post by  Dutchmichael 
#1 ·
Hello everyone, I have a problem in which my 2002 naturally aspirated V6 xterra looses power at lower RPM.

I noticed this a while ago as it would have some hesitation when starting from a stop sign, then I did some light offroading and the truck slowed to a stop going up a steeper hill in 1st gear low range. the motor never died but you could press the throttle in all the way and nothing but the engine tone would change and the truck would not move ( luckily found a different route but barely made it out )

I got back to the road and hit the highway and it was like nothing really happened. Talked to a mechanic worrying it might be the cats and he said it was very unlikely. So I replaced the fuel filter, air filter and cleaned the mass airflow sensor. I also then checked the voltage output of the mass airflow sensor and knock sensor and they appeared to be alright from what I could tell.

This did not seem to help the problem. I had to try to pull out a vehicle the other day and I did not even have the power to spin the wheels.

There are no lights on the dash and it shows no codes. Any ideas?

Thanks!
 
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#5 ·
Thanks for the reply RacerXXL, I put it on a Scanner but it was a cheap one which showed no codes, I may try a better one in the next day or so. The check engine light has not turned on. I hope also to try new spark plug wires today or tomorrow ( I replaced all the spark plugs with quality ones a couple years ago so they should be still good )

Thanks
 
#10 ·
I just got in the new knock sensor and did the relocation. I had one small snag, on the new sensor I had to cut back the wires further as I damaged the wire slightly when stripping. When I did this I found I had one yellow and one black wire as well as a shielding wire. Should I attach the shielding and black wire to the shielding of my spliced cable? Or just the black. I tried it in both configurations and unfortunately it did not solve my problem, and it no longer has any codes after driving for 10 minuets. I will put it on the scanner again after work to see if anything comes up. Any ideas what to try next, or what would be the likely culprit?
 
#12 ·
Well think I have the problem solved. Seems that one of my motor mounts has let go and as a result it would torque over the motor which tore the bottom of the air intake tube after the mass airflow sensor. When the engine was under load it would torque over the engine and open the tube and let in additional air causing poor performance. I also discovered at the same time I have a small leak in my exhaust manifold. Any good links for how to repair\replace a exhaust manifold that? Looks like a nightmare job or not?

Thanks everyone!
 
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