VE Calculations and Lean Codes

I just watched Paul's newest video. Great video, amazing content! Could someone give me a little more insight on VE calculations and how to use them in troubleshooting. I'm not sure if I'm quite catching on. So if you were running lean at WOT, you plug in your engine load and MAF readings and your VE calculations turned out to be good.....then you would focus on a fuel delivery issue? is that correct?

Yes I would be considering a fuel delivery issue.
What vehicle, engine, mileage and year ? Flex Fuel ????

No vehicle in particular. Sorry, that post wasn't thought out very well. I just watched Paul's latest video on lean codes and a dirty MAF and I had so many questions rattling around in my head that I didn't know where to begin. The O2s were lean at WOT so he mentioned it could be either a fuel delivery issue or a dirty MAF, that I understand from reading his book. He mentioned that the VE calculations were low so there was no need to read fuel pressure. So you can use VE calculations to determine your direction of approach? Lean O2s @ WOT and bad VE = dirty MAF? Lean O2s @ WOT and good VE = fuel delivery issue? I know I've seen him test MAFs with scan data by doing a snap throttle test and looking to see if the MAF voltage goes above 4 volts. Is that only valid with a inoperative MAF sensor and not a dirty one? I guess I need to brush up more on MAF sensors and how to troubleshoot them. Is your troubleshooting steps different with a MAF that's dirty compared to one that is not operating properly?

Wood, I have a flow chart I found in a training class manual several years ago that might help. I find that it very neatly explains ScannerDanner's approach, while also integrating Calculated Load.



Hopefully that helps! As far as my diagnostic approach is concerned, Load and VE are the same thing. Both are based primarily on the MAF, and both be low in the case of a underreporting MAF or a engine breathing issue. Both will show high if the engine is breathing correctly and the MAF is reporting correctly. Neither can distinguish between a misreporting sensor and a breathing issue on their own.

There's another thread we had going in the Diagnostic Tools section that's also worth reading. Tons of testing and good info in there:

www.scannerdanner.com/forum/diagnostic-t...s-absolute-load.html

One factoid picked up from the internet on a throttle snap a gasoline MAF sensor signal e should follow almost exactly the same pattern as the MAP sensor signal.

Awesome, thanks Tyler. I've been diggin through that thread you sent me and there is a lot of good information in there and that flow chart really helps me organize my thought process during these faults.

No problem! There's another thread that Noah started that may make for interesting reading:

www.scannerdanner.com/forum/scannerdanne...8-low-power.html#933

Short story, I installed a intake restriction in a Chevy truck, and that flow chart pinned it down.

Blast from the past!

Ah yes, that chart looks familiar.

Where did you see it? I created that about 15 years ago

Did you write that flow chart Jim? That's awesome! Hope it's okay that it is being shown here.

Yep, I made that with Mind Manager back in... 2004? I was a speaker at the first CAN conference in Chicago and made it for that.

Sharing it is fine, but I only see part of it in your post.

I massaged this quite a bit later. That was a while ago and now there are lots of systems that stay in CL for quite some time at WOT. But the principles are the same. There were half a dozen slides that went with it for context as well.

You might see this in an SMP class as well. I use Mind Manager for mapping out classes and diagnostic procedures.

It seems that a lot of technicians have been steered towards VE testing etc. when a 40,000 foot view would serve them better. As a flatrate drive tech, time was everything if I wanted to pay the bills

Here is another one. Remember, these are about 15 years old and I've refined things. My hope here is that technicians would create maps like this to help them think through problems.

I was a slow learner, so I needed it