I am trying to get the family 99 blazer 2wd automatic smogged after an engine rebuild. I have codes showing both banks lean. I am out of ideas short of upgrading the spider. So far I have tried:

Fuel pressure is 62 koeo, 59 running and stays at 60 more than 15 minutes. pump and regulator are a year old.

Used 3 cans of carb cleaner looking for vacuum leaks and there are none.

Pinched off all vacuum lines.

O2 sensors switch back and forth just fine and stay rich or lean if I add fuel or air.

Plugs are AC Delco less that 300 miles on them as well as new cap rotor and wires.

Today we are running a half tank of fuel through it with a bottle of fuel injector cleaner.

Cleaned maf sensor and it runs the same unplugged.

New map sensor.

Cleaned EGR valve..

 

I was getting these codes before my ignition coil went, test it

 

The DTC's indicate a lean fuel mixture on both banks, so you can rule out ignition as being a problem. If ignition fails, (plugs, wires, ignition coil etc) the fuel doesn't get burned, and the O2's report rich. The fact that both banks are lean pretty much eliminates an injector problem too. The chances of having the same problem on both banks, at the same time are slim

Did both DTC's pop up at the same time? If so, the problem is something that will affect both banks equally. Possibly a problem with intrusive air, (air/vacuum leak after the MAF sensor), dirty MAF sensor, etc. Low fuel pressure can also set those DTC's, but your numbers look good. Low fuel volume could be a possibility as well. Possibly a restricted fuel filter, or a problem with the pump. You'd need to do a fuel pump maximum output test and volume test to be sure.

Did you follow the flow chart for the 2 DTC's?

 

I followed the chart but instead of a gauge before the filter I pinched off the return line and got 102 psi.

Tonight I did some more checking and found if I unplug the IAC and MAF the trims fall to +/-2.

Any thoughts on that?


I also changed coils and the module that goes on the same bracket.

 

Car runs WAY better with both unplugged

 

Pinching off the return line applied maximum pump pressure to the diaphragm in the fuel pressure regulator. If it's exposed to more than ~75psi, there's good chance of destroying the regulator, or greatly reducing its life span. Over 100psi, almost a guarantee that the diaphragm is ruptured, the regulator should be replaced regardless. Using the gauge as a dead end protects the regulator when checking max pump output pressure.

Now you need to check pressure and leakdown at the service port AND check maximum pump output pressure and leakdown at the filter using the gauge.

Connect the fuel pressure tester to the service port by the distributor. On your 99, you can activate the fuel pump from the underhood fuse panel.



Connect a jumper wire from the pump prime terminal to battery positive. When the pressure stabilizes on the gauge, make a note of it. Remove the jumper wire and wait 10 minutes, make a note of the fuel pressure.

Connect the pressure tester to the fuel line at the filter. All pressure and flow must end at the gauge. Connect a jumper wire from the pump prime terminal to battery positive. When the pressure stabilizes on the gauge, make a note of it. Remove the jumper wire and wait 10 minutes, make a note of the fuel pressure.

Post the results of all 4 tests, and cross your fingers.

 

There's a service port on the fuel line by the filter for the fuel pressure gauge to screw on to??

 

Nope, for testing maximum fuel pump output pressure and leakdown, you need to do some "creative plumbing" so the tester connects directly to the fuel filter outlet. All pressure and flow must end at the tester. To check regulated pressure and leakdown, use the service port by the distributor. To avoid confusion, it would be best to start a new thread with your specific problems/symptoms mentioned in it.

 

I knew about the service port by the Dist. But from reading what you said, I thought there was a service port by the fuel filter. I was going to be like, damn, I never seen it or noticed it.

But I'll start a new post in regards to my issues.