2002 2WD 4.3 Lean Condition (No vacuum leak)
 

Greetings friends,
My Blazer is running a bit lean and doesn't appear to be a vacuum leak. The lean condition isn't bad enough to fire a CEL, but I want to resolve this issue before it gets worse.

So I want to begin with what troubleshooting I've done so far.

Here we have some data I've collected with the Torque app.
https://cimg7.ibsrv.net/gimg/blazerf...dc5d6d60f3.png

As you can see, the engine stays lean no matter the RPM. This is my first clue that this is going to be a fuel delivery issue. Still, I decided to check for a vacuum leak just in case and it's usually the easiest thing to find. So I got my propane torch and a length of rubber hose and hosed propane all over the well known vacuum leak spots. Around the intake plenum, around the lower in-take gasket, checked the vacuum hoses and pinched off the brake booster. No change or blips on fuel trim data. I decided to use a spray bottle full of water just to double check a few areas and still no change.

SO LETS MOVE ON TO FUEL!

I replaced the fuel filter last year as part of some routine PM. I hooked a fuel pressure gauge to the schrader valve next to the distributor. With the engine off, I cycled the pump on/off a couple of times to get my fuel pressure.

With the pump running engine off I get about 59 PSI.
https://cimg6.ibsrv.net/gimg/blazerf...69bcb86f39.jpg
With the engine running I get about 56 PSI.
https://cimg5.ibsrv.net/gimg/blazerf...d594b47d4b.jpg

And with the engine off after running, I hold about 53 psi for at least 10 minutes.
https://cimg1.ibsrv.net/gimg/blazerf...dab636340e.jpg

So this is about where I'm at. I've read on here the fuel pressure should be around 60-66 psi. Since I'm not leaking down, I feel this is going to be a fuel pump issue and not an injector/regulator issue.

Torque doesn't play nice with the MAF sensor, but at idle it reports ~7 grams per second. Just in case I replaced the MAF with a known good with no changed.

Any idea on how I can further test to narrow down if it's injectors or fuel pump would be greatly appreciated.

That volumnous recitation of a exciting tech jargon was an utter waste of your time.

And mine to read it.

We dont start a diagnosis by playing with tech toys. We start with basic observations.

Your post did not establish the engine is lean.

modern engines are supposed to be lean, its called " lean burn"
The path is:

1. Comments on engine performance while driving
2. Spark plug electrode photos. Spark plug readings are THE most important part.
3. O2 sensor voltages.

Then proceed.

Thanks for the advice.

Engine performance is fine for the most part. A bit slower to react to the pedal than my other Blazer.
I will get sparkplug pictures when I change the oil here before long. They were a bit white when I changed them last year.
The O2 sensor voltages are in the first post.

I've been reading fuel trims should be between -4% and +4%. As you can see in the first post my long terms will near 12%.

Sorry you wasted your time reading my post, but I try to exhaust all avenues I can think of to troubleshoot a problem before bugging someone else for help. And a fuel pressure gauge is hardly a "tech toy".

actually I like what you have shown in your first post and don't consider it a waste of time at all. Yes, your FI system is adding 10% to factory calibration on LT fuel trim but it is effectively adjusting the fuel mix to where it should be. Short term FT is near zero and O2 sensor voltage is cycling across 0.45V. I believe the addition of LT and ST fuel trims is supposed to be10-12 or less. Unless you have a performance problem or SES light on, I really don't think you have a problem.

can we try to get along a little better?

Thanks for the reply! This is really just me trying to find what is going to break next. Really didn't want to change a fuel pump on the side of the road. If you say I don't have a problem I'll gladly stop trying to chase one. Thanks again!