PO171 and 174 99 Bravada

[PaintedStallions]

Well OM, Chris and the gang! I replaced the whole fuel system. I replaced the fuel pump, filter, I went and bought a brand spankin new spider fuel system, complete with the fuel regulator and all. Everyrhing is brand new! Poppets, everything! It turns out that all I needed was the number 5 injector poppet! But needless to say, everything is all new and all is ac delco. I have almost a 1000 bux wrapped up in this thing. I slammed it all in, fired it up and it was sweet! I two stepped it all the way to the gas station, and filled her up and all is good! Now here is the proplem! From the very start after all that time, work and money spent, there was a very slight hesitation when you hit the accelerator. No big deal I thought! All the changed was probably a system shocker and would probably feather out after a couple of miles! Didn't happen! After a couple of hundred miles, the dammed engine light lights up! PO 171 and 174 are the codes. Which means lean system banks 1 and 2! The fuel mileage has plummeted to 12 miles per gallon tops! But other than that it runs like a dream! Through code experience and word of mouth, the fuel pump is usually the blame for those 2 codes to show up together. I did pressure check and all is good on the specs! 62 psi on the norm with the ignition off or on . No leaks or leak downs. As a matter of fact, the leak down test held at 59psi for over three hours. It would have held longer, but I got tired waiting. So what could the problem be?

[danielsatur]

Need to perform a smoke test for unmeter air, or vacuum leaks,see
http://www.automotiveforums.com/vbul....php?t=1040765

If Smoke Test passes, try a new air filter, upstream HO2 sensors, and cleaning the MAF / IAT sensnors.

How many miles are on this car, and when was the last tune up?

[Chris Stewart]

I agree with danielsatur, big vacuum leak,

P0171 1/1 Fuel System Lean
A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

P0174 2/1 Fuel System Lean
A lean air/fuel mixture has been indicated by an abnormally rich correction factor.

I left the clamp off the MAF once, engine ran poorly.

[PaintedStallions]

Well boys! I think I fixed it! Some how I left out the big Oring that goes around the fuel meter that seals the plenum cover! So with that, I went out and bought the plenum cover gasket kit by felpro for 20 bux. I drove it arond for about 30 miles and am still only getting about 15mpg. But its better than 12! This Bravada has about 182,000 miles on it. Very well maintained miles! And it runs like a dream and strong. Now all I have to do is get a rear windshield wiper motor. I have been through about 4 of them so far and they all strip out! Damnedest thing! I will keep you posted on the fuel mileage soon! By the way! I am going to have to try that smoke test thing! It sounds cool! Will it work with a Marlboro?

[PaintedStallions]

I stiil can't get better than 15mpg. Before, I was getting 20 to 21mpg. I drove it on the highway for 200 miles, the same route I always use. I have no codes, misfires, Or leaks that I could detect. It starts on a dime, purrs like a kitten and has good power. Any ideas?

[danielsatur]

If Smoke Test passes, try a new air filter, new upstream HO2 sensors, and cleaning the MAF / IAT sensors.

[PaintedStallions]

Ok! I cleaned the MAF. But where is the IAT sensor and what is it? And what is the best way to clean it?

[danielsatur]

Originally Posted by PaintedStallions

Ok! I cleaned the MAF. But where is the IAT sensor and what is it? And what is the best way to clean it?

The Incoming Air Temp (IAT) is usually in your Air duct work from the air box to the throttle body, or it's housed in the MAF sensor.

It's a 2-wire temp probe.