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Code PO171 troubleshooting?

friendco

NAXJA Forum User
Location
South Orange, NJ
Just pulled the code at autozone and its the P0171 "Fuel Trim Bank One Condition"
1) fuel pressure or MAF sensor
2) Oxygen sensor
3) Ignition misfire-repair
4) Fuel injector problem

Any ideas of some basic troubleshooting I can do to find out which way to go with this? Thanks alot

96 cherokee
160,xxx miles
auto tran, straight 6
 
no maf sensor on the xj

i would say front o2 sensor.

fuel pressure can be tested with a gauge.

misfire or bad injector, the engine would skip/miss at idle or under load. would also show a discolored spark plug
 
I did notice the other day while on the highway sitting in traffic some slight chugging which actually shook the chassis, if its just a misfire should i replace the spark plugs or is it all due to the injector?

thanks for the help
 
I did notice the other day while on the highway sitting in traffic some slight chugging which actually shook the chassis, if its just a misfire should i replace the spark plugs or is it all due to the injector?

thanks for the help

i dont like just throwing parts at it.

so, when was the last tune -up? throttle body/topend cleaning, o2 sensors??
 
actually just purchased about a month ago, they hadn't changed the oil in about 6 thousand miles and I'm sure it hasn't had a tune up in a while, I'll take it in soon for that and in the meantime I heard I should run some injector cleaner through ?
 
An upstream O2 sensor fixed my P0171 problem a couple years ago. I used a Bosch universal from AutoZone and it's still going fine.
 
I'd do a tune-up to it anyways. All of the parts needed should be around $80. Worth it. You should think about replacing the fuel filter while you're at it. They're cheap and when they get clogged they can cause some issues.
 
Well, no I really have not, and the more I read, the more it sounds like that MIGHT be my problem....I stress MIGHT because of 2 reasons, first, I don't know how to accurately test a MAP sensor and second, I DID unplug the MAP sensor and there was no change....but I don't know if that means its good or bad.
 
Just worked on my neighbors Dodge Dakota...downstream 02 sensor was bad...was giving same trouble code of P0171 saying that truck was running lean, so computer kept adding fuel and made the truck run rich...you could tell by looking at the tail pipe that it was running rich (black sooty tip) and mileage had gone down...we were able to see that the sensor was not switching at all using an autoxray scanner that monitors sensors while running... it had gone bad because it was contaminated with power steering fluid that had worked it's way into the wiring harness from a bad power steering pressure sensor.
 
'Just worked on my neighbors Dodge Dakota...downstream 02 sensor was bad'..............
Do you mean the first, or 'upstream'? The second, or 'downstream', usually in the tail end of the cat, offers nothing other than if the cat's working. The first is the one that controls the mixture, and they only have a lifespan of 60k-100k miles, and many times do not set a code, as their demise is gradual, Your PCM 'learns' to live without it, degrading fuel economy, and ruining your cat due to rich, cool fuel mixture.
 
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