MAF sensor and related codes

[Independence]

Good morning,
Hoping someone may be able to shed some light on a recurring issue that's plagued my new (to me) truck recently.
1998 7.4l 454, no engine mods, new plugs, wires, paper air filter from local parts store, all fluids changed. Getting a MAF sensor code on the OBDII scanner, so I replaced it with whatever advance/auto zone had available, cleared the code and it reappeared 30 miles later. Seapped it out for another new one, same result. Thought maybe it was an off brand, so I ordered an AC Delco MAF from Summit, same procedure resulted in another code along with running VERY rich on both banks after 20 miles or so.

Any help would be appreciated. Wires look like they're in okay condition (it's 24 years old afterall), and I made sure the connection was clean.

Thanks!

 

[454cid]

Replacing a part based on a code for that part is not the way to go. It could be the part, it could be the wiring, or it might be something else effecting the reading that part is getting.

You need to use a scanner that will give you live data and/or share the specific codes you're getting. How are you determining it's running rich on both banks?

When I had MAF problems, I did end up replacing it, but I had already proven to myself that the MAF itself was the issue.....readings I was seeing while the truck was running and borrowing a known good MAF completely eliminated the problem.

Try running your truck with the MAF unplugged... the PCM should switch to speed density to do it's thing. That might save you from running super rich in the mean time. My truck would run rough, then throw a code and start running better. I think it was determining the MAF was bad itself, and switching to speed density with it still plugged in.

 

[stutaeng]

Ditto what @454cid said. I've used this procedure before for checking MAF functionality, but on a 5.7 Vortec prior to getting a scanner that lists MAF values. https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/how-to-test-the-maf-sensor-2

The 7.4 will be calibrated differently, but I'm sure you can at least check for 12+, ground and see if the numbers change as you rev up the engine. Note that you need a DVOM with Hertz capability. Otherwise you need a scanner, or just take it to a shop so they can check for you.

Good luck.

 

[Pinger]

Which code? I had P0102 which was nothing more than a missing fuse.
If the 7.4 is the same as the 5.7 it shares a live feed with the O2 sensor heaters and the EVAP.

 

[Independence]

All good thoughts thank you! Was trying to avoid dropping it off at a shop for a scan, and I haven't been able to get good readings from the MAF pigtail due to its positioning facing the firewall.

I know it's running rich because 1, my eyes burn with rich exhaust smell and 2, it's throwing the code for left and right bank running rich.

I didn't know it shared a feed with the evap, maybe I should research that more thoroughly.

I also have an open female connector (with nothing to plug into) near the MAF sensor wire harness.