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2000 X bad idle, bad mpg, did everything!

2K views 9 replies 6 participants last post by  kms1990 
#1 ·
So I hate doing this but I am at a loss with this. I have searched and searched and done all the recommended stuff but still not change. I am not even remotely new to building and modding cars so the fact that this is stumping me is really pissing me off.
-has just over 100K miles.
-no check engine codes.
-Idle’s like crap will die occasionally at idle.
-Drives and accelerates fine.
-Gets about 120-140 miles per 16 gallons of gas.
-mods are CAI, and muffler
-I have replaced: plugs (ngk), wires(oem nissan), distributer(a1Cardon), fuel pump(bosch), fuel filter(bosch), cleaned MAF, radiator(dayco) and timing belt with all associated bits.
Still idles like crap and still gets poor mpg. Help!!!!! My Audi was easier to fix then this thing is.
 
#3 ·
5w30 i think. After driving it a little while after changing the pump it got better but is still not right. If the knock sensor is bad im gona do the risistor. Pcv valve is not a bad idea. Ill order that along with the upper manifold gasket. I dont think its the KS though because there is no loss in power semse before it started running like crap
 
#4 ·
Maybe the egr is you issue. Even the vac hose going to it can cause issues.
Keep us informed, as the more info you have for us the better the help we can give.
ps. It is not the knock sensor!
 
#5 ·
Try replacing the MAF sensor. I was having the same issue. Just cause you cleaned it doesn't mean its good. Mine looked fine but when i replaced it my truck ran like a champ. If it doesn't fix the issue you can always take it back to the store for a refund.
 
#7 ·
Maf is not a bad idea. Only issue is im in korea so returning it is not an option. If you unplug it will tge ecu revert back to cold start mode like some cars do?
Not sure what the cold start mode is but if you unplug the MAF and try to start it they will generally not run. If you unplug the MAF while running the truck will die. Unplugging the MAF while running, allowing the truck to die, turning off the key, plugging the MAF back in, and then re-starting the engine will clear all of the stored/learned values in the ECU.
 
#8 ·
I ask because on some cars like audi's for example if you unplug the maf the ecu will revert back to cold start mode when it doesnt read the maf at all and runs the motor based on presset readings. Helps a lot to daignose a bad maf. Sounds like the xterra will not work that way.
 
#10 ·
i agree on replacing the maf sensor also check if your gettin p0325 or p0328 codes (dont turn on light) and as you said do the bypass if you do, see if that helps, but mine has a p0325 code and i get 15.5-18mpg. also try cleaning your throttle body seafoam makes a throttle body spray that works great for this. you may also try the diy seafoam in the diy section here it may also help, since you have no cel it cant be anything too major.
 
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