Utinator

So, I just ordered the newest HP Tuner (PRO) program. Once I get it, I plan to help my parents diagnose their 2003 5.3L Suburban issues. I also just want to keep an eye on my LS1 Camaro. I don't really know what to look for, so I'm hoping to find some basic information about these engines.

What are some "safe/normal" parameters I should be looking for? Some specific parameters I'm talking about are fuel/air ratio, and fuel pressure (at the rails).

Lethalwx69

For the basics Youtube is excellent resource.

https://www.youtube.com/playlist?lis...pevsn7pCydhwtT
https://www.youtube.com/user/TheTuningSchool/featured

Utinator

Yeah, I plan on watching lots of YouTube. I already found one very helpful video posted by HP Tuners.

So, what should the air/fuel ratio be on an LS motor? Where can I find that kind of info?

DFORESI

Well you won't really be able to get an accurate read on the AFR using the stock Lambda sensors. All they're good for is telling you if you're rich or lean.

Something you may want to look at is the long term and short term fuel trims (LTFT, STFT) these will tell you how much the closed loop system is adding or taking away fuel. It's okay if these terms are populated but if they're maxed out and no longer providing compensation then you're likely to be running less than optimally.

DFORESI

To answer your other question.

At a cruise you should be running close to lambda of 1, or roughly 14.5 with E10

When you're in PE then you should probably be around lambda 0.8 or roughly the high 11's in AFR

Again, you won't be able to read any of this on the factory narrow band sensors (accurately anyway). I'm pretty sure that when you are in PE the car runs in open loop anyway because it can't really tell if its hitting its target EQ ratio

Utinator

Do I need a Wide-Band sensor to get an accurate AFR reading? I have the HP Tuner "Pro" model, so I can add a Wide-Band if I need to.

DFORESI

Yes you need a wide band to get an accurate AFR. The question you need to ask is why do you need to know what the AFR is? What is wrong with the car? Have you started with the basics and pulled the DTC's? Where does that point you?

Utinator

I haven't gotten there yet. I'll probably hook up to their Surburban next weekend. They said it smells like it's running rich, and has some O2 related codes. They have changed all 4 O2 sensors (in the exhaust), all 8 spark plugs, wires, and coils. A local GM dealer replaced the PCM (the old one died last year). I think my step-dad said he replaced the cats too. It still runs a little rough some times, and the check engine light stays on.

I was thinking that the MAF might be going bad, causing the PCM to dump too much fuel. I was hoping to use HP Tuners to "see" what was going on.

DFORESI

If that's the case then you'll want to see how big the error between the MAF calculation and the VE calculation is. The VE shouldn't really change if the vehicle is stock (other than a super dirty air filter), so if there's a large delta between the two, your MAF could be on its way out.

Utinator

Thanks. I'll look for that.

The MAF went out on my LS1, but it caused my engine to run lean. I just couldn't think of anything else that would be wrong with this Surburban's engine.

DFORESI

Different issues.

Your Camaro sounds like it was modded based on your signature. The only way any of those mods were going to make more power was by increasing the airflow to the engine. So if you had all that work done and were running a MAF tune and then you're MAF died, it's going to default to your VE table. Because of your intake and heads, etc, your engine is going to be flowing more air than your VE table would indicate, but without the MAF the PCM doesn't know this, so you're going to inject less fuel than you need a run lean.

I assume the suburban is stock. So I don't really think a MAF failure would result in the same behavior. That being said, if it IS STOCK then when it runs the VE table it shouldn't be running so rich that you can smell it.

Utinator

My MAF died before all the mods. My Camaro is on Speed Density now. The Surburban is stock.