Getting a P0171 on my 99 Silverado

[88LT1Blazer]

I was getting a P0171 code on the truck. It has the 5.3 liter. I had checked the internet on possible fixes. First and most common is the Mass air being dirty. I cleaned mine and really was not very dirty to start with. Codes still popping up. I checked the bank 1 sensor 1 and found it to be white in color. So, the O2 was doing it's job. Then checked the plugs. The whole set was a little white and had a little bit of trash on them. Then check fuel pressure. THAT was the problem. I was getting 60psi at the prime and quickly would fall to 50 psi. Then started the engine. It showed the engine running with only 48 psi. Now I know why my scanner was showing that the ecm was trying to add fuel all the time. The fuel rail would bleed down to almost nothing in about 10 minute. That is when it pointed to the regulator. I changed it and the problem is cleared.

This is just to help others in a similar issue.

[Rickracer]

Good Job Kent, :thumbsup: :cool4:

[88LT1Blazer]

Yeah, the fun part was changing the regulator in the parking lot of Orielly Auto Parts.
I had bought the last one they had in stock and hated to even drive the truck knowing it was running that lean.

[Diabolical]

Excellent info bro!!

[BUTCHERBOY]

Good fix Kent.

Start calling you Dr. EFI!

Justin

[88LT1Blazer]

It also had to do with clogged injectors too. The upper stuff helped for a while. I had to swap out the injectors from a project engine. Running like a champ.

[sbctols1]

Good to know, I have the same truck. What's the mileage on yours?

[88LT1Blazer]

190K and running like a top!!

[sbctols1]

Mine has 53k on it. Have you had any major problems with yours up the 190k?

[88LT1Blazer]

NOPE!!! I have to pull the pan when I get home. The previous owner put too thick an oil and the O-ring is leaking by. I have 10w-30 in it now. When it dips below 40 degrees outside, the oil pressure wanders. Once the oil warms up, it stays steady. Like I said, need to pull the pan and the O-ring for the pick up tube. Change the O-ring and re-torque the pick up tube. Then a new gasket for the pan. Everything I have read about oil pressure wandering and low appon start up normally is the O-ring. Are you having issues? I can surely help.

[sbctols1]

No problems yet. I have only had the truck for about five months now. I bought it with 50k miles on it. I am not new to LS engines (see sig) but am new to these trucks. Have you had any problems with your gas gauge?

[88LT1Blazer]

Yeah, the one in my 99 shows the full spectrum. The problem is empty at just under quarter. There is a kit I seen on Ebay that you can replace the stepping motors to repair the cluster. That is the only issue with mine.

I seen that in your sig and the avatar.

When I got my truck, it was mushed on the front. The previous owner hit a deer and had no money to fix it. I trade him a Ford ranger and got the truck as it was. Redid the front. Replaced the passenger fender, core support, radiator, condenser, lights, grille, water bottle, and the air box. I had picked up a complete front cap the same color as the truck for $500 and then sold the rest of the parts I didn't need.

The next thing I was to do is the electric fan swap from the 05+ trucks. I have the fan and the harness from a 06 truck. The only things that are missing is the two pin connector that runs to the ECM plugs for the temps and to turn mine on in the ecm.

[sbctols1]

Is the fan swap a plug and play deal? That sounds like an awesome mod.

[88LT1Blazer]

To my knowledge, you have to have the 34" wide radiator core. You need a fan control harness. There are a couple sites I know sells them. You need to add to pins with wires attached to the the ecm plugs. You just have to run the control wires from the ECM for the low and high temps. The fans mount along with the same radiator bolts on top. Then of course, you have to program the ECM to run the fans at the desired temps. Not sure that the temp settings are in there on the older trucks. These fans are a huge twin fan set. The aftermarket harness wires the high setting on temp and the a/c compressor.

[smsmith36]

I have a 2000 with about 130,000 on it. The only problem so far is the odometer and gear display in the cluster is out. Sometimes if I press the trip reset real fast a bunch of times it will come on. It might stay lit a couple minutes or a couple days.