HORRIBLE gas mileage..and bank one is running lean..help please

[nomiezvr4]

Hey guys I have a 98 T&C with the 3.8 motor. It has fresh plugs, wires and an airfilter. 88,000 miles.

I just bought it a week ago and the other day it threw a check engine light. I believe the code is P0171...which means that the bank 1 is running lean if I recall correctly. Anyways, since the car is averaging around 6mpg(according to the car and my own mpg testing) I decided to check the upstream oxygen sensor because maybe it was shot.

I pull the 02 sensor and it was black as could be. The car is obviously running very rich. Why?

I have checked for any leaks on the intake manifold, intake pipe and everything else I could think of that could've been sucking in air before the intake manifold, everything looks OK.

Funny thing is, the oxygen sensor looked fairly new, like only a few months old. Ive been doing a little reading here and there, and people are saying that the po171 code usually indicates that the fuel pump is on its way out..but will that cause HORRIBLE gas consumption?

I want to check the fuel pressure tomorrow, but I was wondering if you guys could throw me any other ideas...thanks!

Nomie

[RIP]

http://www.obd-codes.com/trouble_cod...gen-sensor.php

[nomiezvr4]

Hey thanks for the quick response, but I dont think the Town and country has a MAF sensor. I believe it uses a MAP(manifold absolute pressure) sensor. I'll check the fuel pressure then go from there. Ill keep you guys updated..

Nomie

[Rawtorque]

It could be a fuel injector stuck open. Or the coolant temperature sensor.

The one bank lean sure sounds like it's trying to make up for a rich injector. ALso look for leaks in the EXHAUST manifold. Yes, that can throw off the O2 sensor loop.

I think it has both a MAP & MAF sensor. A bad MAP (manifold absolute pressure) will also kill mileage.

You could try (engine & key off!) disconnecting the wire harness to the MAP. This will force the computer to use a fixed value for the MAP. Start it up & see if it runs better. But this will also set a fault code, which can confuse anyone working on it later, so warn them of what you did.

I hope you replaced the O2 sensor since it's probably all gummed up anyhow.

[Steve J.]

PCV stuck open? That would probably effect both banks though.

[RIP]

Originally Posted by nomiezvr4

Hey thanks for the quick response, but I dont think the Town and country has a MAF sensor. I believe it uses a MAP(manifold absolute pressure) sensor. I'll check the fuel pressure then go from there. Ill keep you guys updated..

Nomie

Yup. MAP. Serves the same purpose as the MAF. They say the MAF/MAP sensor but I've read more often than not there's a vacuum leak downstream of the sensor if it's a MAP related problem.