Diagnose Lean Conditions

Duck Vader · Post by **Duck Vader** » Wed Oct 21, 2020 9:54 pm

So did a log on the truck back in beginning of Sept and my max longft1 and longft2 were at 17.19%. Really high.

Tightened down the CAI, and it hit 20% - even worse.

Redid the CAI, clamped down the broken bolts for the exhaust manifold, ran fuel system cleaner, installed a new intake manifold gasket, and just ran another log - 17.19% on both trims.

I can't find any leaks.

What else should I be looking at?

Don't know what to do next to try and fix this.

Duck Vader · Post by **Duck Vader** » Wed Oct 21, 2020 10:11 pm

Replace maf?

Duck Vader · Post by **Duck Vader** » Wed Oct 21, 2020 10:39 pm

I think I have a fuel pressure tester somewhere. I'll hook that up tomorrow night if I can find it. Maybe I have a weak pump or clogged filter?

vr4 · Post by **vr4** » Wed Oct 21, 2020 11:09 pm

Log calculated load and g/s on maf. That truck should see around 200g/s. Last one I had was reading 160. It was low enough for a low power complaint but not enough to trip a cel. I'm going by memory on this.

Still the first thing I would have done is a new GM maf. Not aftermarket.

Duck Vader · Post by **Duck Vader** » Wed Oct 21, 2020 11:32 pm

Ordered a Delphi AF10043 Mass Air Flow Sensor

That should be oem.

As for fuel pressure it's fine. Just tested it.

Maf will be here tomorrow.

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 12:04 am

Also pretty sure I have a vacuum leak somewhere. Heard a hissing sound when I started it up to test the fuel.

vr4 · Post by **vr4** » Thu Oct 22, 2020 12:40 am

[quote=""Duck Vader""]Also pretty sure I have a vacuum leak somewhere. Heard a hissing sound when I started it up to test the fuel.[/quote]

Watch fuel trims. Vacuum leak will show up lean at idle and normal ish at elevated rpm.

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 4:09 pm

Plan is to replace maf sensor tonight, recheck vacuum lines, reset ecu, then drive it to/from the gym for a few days and see what it reads. If still lean I got a tune from my guy to fix it so everything runs better until I can figure out what is causing it.

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 4:46 pm

Anyone have experience with those $100 evap smoke machines on Amazon?

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 4:50 pm

https://www.amazon.com/dp/B06XHRBKTM/re ... KFbT16XXG3

Chris GTO TT · Post by **Chris GTO TT** » Thu Oct 22, 2020 4:54 pm

Might have to look into one of those too

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 6:45 pm

https://www.amazon.com/dp/B00UJVDZWK/re ... UTF8&psc=1

Kind of debating on this. Would be great to have over the years but not sure if I want to spend that much money on one.

vr4 · Post by **vr4** » Thu Oct 22, 2020 7:28 pm

[quote=""Duck Vader""]https://www.amazon.com/dp/B00UJVDZWK/re ... UTF8&psc=1

Kind of debating on this. Would be great to have over the years but not sure if I want to spend that much money on one.[/quote]

Wow that's cheap.

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 7:56 pm

I know it is for what they normally cost but 300

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 8:33 pm

If the maf sensor doesn't work to fix it, im going to probably order one.

While I replace the maf tonight I'll go over all the tubes I can find and look for any cracks but last time I checked I didn't see anything

aaronatstate · Post by **aaronatstate** » Thu Oct 22, 2020 8:36 pm

Why spend the money on it, when they have these places that have all the equipment already that will use it on your vehicle and tell you what is wrong for a small fee.

I mean shit, you live not far from Steve, take it to his place and get it diagnosed if it is still a problem. I am all for trying to fix things myself, but when you start needing specialized equipment that you are hardly every going to use, then it's time to let the pros take care of it.

Duck Vader · Post by **Duck Vader** » Thu Oct 22, 2020 9:49 pm

My issue is that I could use it over and over again for years on different vehicles.

alienviking · Post by **alienviking** » Thu Oct 22, 2020 10:39 pm

...but would you though? I am willing to bet 9 out of 10 times people say that they end up not doing it and end up spending more money and time on it than it would have cost to get it done right by somebody else to begin with.

Duck Vader · Post by **Duck Vader** » Fri Oct 23, 2020 12:21 am

Average shop charges $100 to diagnose. If over the life of the tool I use it 3x it would pay for itself.

That said.

It sounds like I have air coming from the vacuum on the top center of the intake.

Put in the new maf sensor as well.

Problem is I went to reconnect the battery and the negative cable bolt broke/stripped. Ordered a new one off Amazon for tomorrow delivery. Hope it's the right one.

Duck Vader · Post by **Duck Vader** » Fri Oct 23, 2020 12:26 am

I think it's the pcv valve line and where it connects to the intake. That's where it kind of sounds like it's leaking/whistling.

Any ideas on how to check without smoke?

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