importsmasher

My 97 Mustang convertible's check engine light is on. I had the codes read, and it is P0171, or lean condition on Bank 1. I did a quick search, and most of what I found with that code also had driveability issues. My car has no driveability issues whatsoever; it runs great and is getting 23-25 MPG (most of my driving is highway driving).

I am contemplating just replacing the Bank 1 oxygen sensor (haven't gotten around to it yet), but I thought I would check here first, in case there's other things I can check.

Any input is appreciated. Unfortunately, I don't have a lot of diagnostic equipment; all of my other cars are 60s and 70s cars.

Thanks,
Importsmasher

dawson1112

Before you go replacing 02 sensor, I would spend a little time looking for vacuum leaks. P0171 is the pcm telling you that the PCM's Adaptive Fuel Strategy has reached its rich calibrated limit for bank 1. That means it has detected a vacuum leak weather its real or perceived. It could even mean you have a dirty or partially clogged injector.
( 9 times out of 10 its a vacuum leak at the intake or an exhaust leak just before the 02 sensor. )

You may not notice any drivability issues with p0171-p0174 codes but you may start to notice your fuel mileage is decreasing as the pcm is dumping more fuel to remedy the lean condition.

Some things to check are air leaks in the air intake tube after the maf, cracked or broken vacuum hoses. But most times when you only get the Bank 1 p0171 code that means that there is a vacuum leak at the intake gasket.
Also a dirty fuel filter may cause the code, but usually that would generate both p0171 and p0174.
I had that p0171 code on my current 2000 gt and it was caused by a leak at the intake gasket. All I did was pull the intake, and since the gaskets are rather expencive, I used ultra black on both sides of the old gaskets and reinstalled the intake and the problem went away.

Obviously its easier to diagnose a lean problem if you can get your hands on a mid level scanner capable of reading long term fuel trims and live sensor data.

importsmasher

Thanks for the input! I will take a look for any vacuum leaks. I don't hear any exhaust leaks; the car is quiet as can be. I will run some fuel injector cleaner through it to see if it is a dirty injector.

Thanks again!

Importsmasher