How to eliminate first start MAF trip?

[BrodyO]

All,

With my turbo setup I don't have a MAF sensor. I'm working to turn my 02 sensors back on and get running closed loop again but one thing that's always been annoying is the first startup after reconnecting the battery/reflashing the ECU. For the engine to run properly, it's gotta run for long enough it see's the mass air flow sensor fault P0102, cycle the key and then it will run properly. When it's trying to run on that first start it will sit there and run extremely lean with the throttle most of the way open. It's kind of embarrassing for people to hear it running like that and it's not advantageous when I'm at the track and trying to make a really quick change to get back up to the line and run again.

Any way to skip the first startup step? Even if there was a way to trip the fault immediately so it only runs crappy for a couple seconds, then sorts itself out without having to restart again?

Thanks

Colorado_7875_VVE_2Bar_SEPpro1000cc_Rev5.hpt

[hjtrbo]

There is a shit tonne of info in here on how to correctly fail the maf.

[blindsquirrel]

screenshot.12-04-2024 21.09.50.png

[hjtrbo]

screenshot.12-04-2024 21.09.50.png

On a plate. You're in a good mood today

[LS ROB]

On a plate. You're in a good mood today

[blindsquirrel]

What? I'm always in a good mood, I'm just (often) misunderstood.

[hjtrbo]

Lol, we all are in one way or another, but some more than most

[blindsquirrel]

And another tip: definitely do not zero out the MAF table, especially not the first cell.

[Lakegoat]

I would also go to Engine Diagnostics--Airflow--P0086 and make that 8000rpm.
I zero out the maf table except the first two cells. Here is a screen shot. I have tried as high as 15 in those two cells and seems to make no difference. Car starts first time everytime and does not require a restart.
Is your IAT sensor in the manifold somewhere?

[edcmat-l1]

Setting all the fail parameters works in almost all GEN4 cases. They're not near as finicky as GEN3s. Some of those can be a real pain. No rhyme or reason, just one will be a PITA and the next one won't. I tend to think it's some background stuff. I've fixed them by doing a GM update then applying my changes, and I've fixed them by replacing entire PCMs and starting over.

I'll zero the entire MAF sometimes, sometimes I'll leave the first few cells. If I zero one completely and it gives me a problem on first try I go back and populate the first few cells of the MAF.

[LS ROB]

What type of issues can arise when zeroing out the first few cells when failing the MAF? I normally do zero the whole table but am probably just too novice to recognize the side effects.

[blindsquirrel]

Runs poopy until it sets the code. Mine did, anyway. It would also run poopy on the first start if it sat for ~2 weeks or so even without being reflashed or codes cleared. Cranking and letting it run just long enough to chug a bit, then key off, then on the next start it would be smooth like nothing ever happened. It wasn't a fuel prime issue either, a key-on/key-off without cranking to run an extra prime cycle did not change anything, only letting it actually try to run.

[BrodyO]

Thank you, you guys rock. This thing is getting better by the post. Starting to have a really fun, streetable truck with good manners and plenty of power.

[LS ROB]

Runs poopy until it sets the code. Mine did, anyway. It would also run poopy on the first start if it sat for ~2 weeks or so even without being reflashed or codes cleared. Cranking and letting it run just long enough to chug a bit, then key off, then on the next start it would be smooth like nothing ever happened. It wasn't a fuel prime issue either, a key-on/key-off without cranking to run an extra prime cycle did not change anything, only letting it actually try to run.

Ahh ok. As always, appreciate the insight.

[edcmat-l1]

Runs poopy until it sets the code. Mine did, anyway. It would also run poopy on the first start if it sat for ~2 weeks or so even without being reflashed or codes cleared. Cranking and letting it run just long enough to chug a bit, then key off, then on the next start it would be smooth like nothing ever happened. It wasn't a fuel prime issue either, a key-on/key-off without cranking to run an extra prime cycle did not change anything, only letting it actually try to run.

Most GEN4s don't have that problem. Every once in a while I run into one that does. And with both the GEN3 and GEN4s they only do it after a memory reset like a flash or a battery reset. After that they're fine. If they do this, you can rapidly pump the throttle pedal like it's a carb and you're pumping the accelerator pump and it helps them set the code and take off.

[blindsquirrel]

Yes, but mine did it after sitting parked a long while and after repopulating the MAF table with stock numbers it stopped doing that. I'm unaware of any glitches caused by NOT zeroing the table, but I am aware of glitches that CAN happen, sometimes, if it is zeroed, so why zero it?

The only reason in favor of zeroing it is as a test, when the MAF is still installed but there's a question as to whether it's truly failed or not. If it only runs with numbers in the table but does not run with it zeroed it's a useful test (though there are also probably better ways to tell that). It's just as a diagnostic under that very limited situation.

[Alvin]

I've not had that issue where a SD car wants to start with MAF in a long long time. There must be something about how I'm failing the MAF.

I'm very aware of the issue. GTO's always seemed worse about it to me.

For the longest time I was failing the MAF low = 1 I've just switched back to using 0 in the past year. Prehaps something like that is it.

[blindsquirrel]

I imagine there might be different results depending on whether it's just temporarily failed for tuning or totally permanently removed.

[Alvin]

I imagine there might be different results depending on whether it's just temporarily failed for tuning or totally permanently removed.

When you have this problem and there is no maf on the car it gets super pissed when you try to crank it after a battery disconnect.

I use a template to setup GEN 3-4 in SD. If someone has a known file with this issue I wouldn't mind applying it just to see if it fixes it... for science lol