P0171 code
 

Ok, so I been battling this fight for a few weeks now.

Rough idle, hesitation from a stop. Blows smoke when accelerating. Goes thru gas likes it free. Black gunk come out the tail pipe. Driving it, it will studder, lose power briefly. SES light is on, code is p0171 - Bank 1

I did a complete tune up on it when all this first started. Swapped out spiders to the newer MFI style. Im at a lose of what else to do. Im getting ready to order a new fuel pump and try that. I put a pressure gauge on the service port and turned the Key ON, pressure went up to 63psi, but started to drop. I know thats bad.

I read some where to clean the MAF sensor.

Any suggestions.

Clean the maf, check for vacuum leaks, change the pcv, check and clean or replace the egr.

Key on, engine off, fuel pump running, regulated fuel pressure must be 60psi to 66psi. Your reading of 63psi is good. The second part of the test is just as important. The pressure must remain above 55psi for at least 10 minutes after the pump shuts off. If it passes both parts of the test, the fuel delivery system is doing its job and we can continue diagnosing. If it fails one or both parts of the test, it indicates a problem. It does not tell us what the problem is, only that a problem exists. Post your results.

The P0171 indicates a lean condition on bank 1, (driver side), but all the black smoke indicates a rich condition. Oxygen sensors produce voltage after they are warmed up: low voltage if the mixture is lean, and higher voltage if the mixture is rich. If the sensor is failing, or doesn't warm up, it will indicate a lean mixture. When the sensor indicates lean, the PCM richens up the mixture. Fuel trims and the sensor output need to be tested with a scan tool to determine if it can react to changes in fuel mixture. This flow chart will help: https://blazerforum.com/forum/diagno...plained-35154/

fuel pressure drops, right away, doesnt hold.

Next step is check fuel pressure and leakdown at the fuel filter outlet, (forward end of the filter). The pressure tester must be modified so it will connect directly to the fuel filter. All fuel pressure and flow must end at the tester. Most auto parts stores stock this item, you'll need one: Dorman Products - 800-121 When the pump is running, pressure must be 73psi to 108psi and it must remain above 55psi for at least 10 minutes after the pump shuts off. Post your results, they will determine if the problem is in the plenum, or in the tank.

Ok, maybe I'll understand on how that piece attaches to my fuel pressure gauge when I see it in person. But I'm a little confused. Can I get a bit more explanation or picture about that piece.

When I want to test the pressure, do the samething, Key ON and watch the gauge??

This is a tester that I made a few years ago. It attaches inline at the fuel filter. When the valve is closed, it isolates the pump from the plenum. Maximum fuel pump output pressure and pump leakdown is indicated on the gauge. When the valve is open, it indicates regulated pressure and system leakdown, just like testing at the service port by the distributor.

Attachment 31494

The fuel pressure test kit I have is the Fuel Injection Pump Tester from Harbour Freight Item # 92699. It comes with various hoses and adapters. Will one of them fit or work???

Yes, key ON, (obviously engine off, no fuel going to the engine with the tester connected like this) and the pump running.

I think that kit has a brass adapter that will attach to the tester, and has a 3/8" barb on the other end. The Dorman connector in the link above will connect to the fuel filter outlet, and you'll need a section of 3/8" fuel injection line to go between them.

Ok thanks, I understand better now. I'll try and rig that up tomorrow and see what happens.