1997 2.7L Tacoma

I’m getting a po171 code. Fuel system lean bank 1. Changed out bank one sensor one. Still getting it. Sprayed the whole engine bay with ether and brake clean to check for intake leak/vacuum leaks. None. Any suggestions?

 

Possible brake booster leakage. You are going to need a scan tool and a pair of large pliers. While monitoring STFT (short term fuel trim) squeez/plug the booster vacuum line and see if the trim drops.

 

Thanks. So if it drops it’s the brand booster?

 

Yes, I like to squeeze the hose with pliers so that I can see if the STFT reacts or not. If not then start to look to see if the evap purge valve is stuck open.
This code is a "symptom" of a problem. It is telling you that the PCM has reached its limits of adjusting the fuel mixture and it can do no more, could be a vacuum leak, could be low fuel pump pressure, could be ???... this is where a diagnostic tech earns his pay whereas a parts re-placer just starts putting parts on hoping for a fix.

 

My long term trim is roughly 39% and my short term is 14%. Pinched off the lines to the brake booster no increases in the trim.

 

If there was a vacuum leak at the booster and you clamped off the line the STFT would decrease from 14% to a lower number. Clean the MAF sensor with MAF sensor cleaner and take the air boot off from the MAF to the throttle body and examine it for cracks, if it is rock hard, replace it.

 

Started digging into it I have low fuel pressure and the pump is failing. Which makes sense why it’s lean. Only 30psi on the supply

 

Ding ding ding... now comes the real question, drop the tank or lift the bed. I like lifting the bed as dealing with 20+ year old fuel lines, fittings, connections can turn a mistake into a very bad day.

 

If/when I need to RR my fuel pump

im going the removing bed method

 

If this was a rolling POS like my buddys S10... we cut a window in the bed.

 

I pulled the bed off my truck by myself before (it’s super easy with 2 people). It’s really not that difficult and is definitely the way I would go to access the top of the fuel tank.

 

Drop the tank

 

glamisman
i remember while back some member had a S10
FP went out so many times he could install RR FP in a parking lot in a couple hours......by himself!
IIRC fuel pump was a known weak point on the S10(??)

he posted some pix where he carried some thick 3ft high wood blocks with him
he would tilt bed and place blocks on one side of bed resting on frame.....RR's pump....and drop bed back down

after seeing those posted pix....RI bed is way to go

that 'cut method' great idea too
many older F-body GM owners do the same
instead of dropping tank/exhaust/rear end/axle shaft
makes total sense