HydroStream6

iTrader: (16)

I'm doing a MAF tune on my Silverado. I haven't tuned for a MAF in quite a while as I've been doing everything lately in speed density.

Anyways, I dialed in my VE (primary and secondary are identical) with the MAF unplugged and going off the LTFTs and STFTs. Engine runs very well in speed density except it doesn't want to idle for some reason even though AF there looks good.

Anyways, I plug the MAF back in after getting the VE dialed in so I can start tuning boost and it runs like garbage. Fuel trims are going nuts, truck will barley run, idles even worse. I swapped the MAF with another unit and it acts the same. Runs extremely lean.

What could cause this? The IAT is in the MAF so I'm thinking fuel is being pulled via IATs somewhere but I can't find anywhere that it is. Any other thoughts?

I've attached the tune that has the VE dialed in.

I'm all ears, this is driving me nuts. I may just end up going to a 3bar SD OS and get rid of the MAF.

HydroStream6

iTrader: (16)

Oh and another thing. Why does the trans shift extremely hard with the MAF unplugged??

salemetro

iTrader: (5)

You should be tuning with the MAF plugged in, but disabled in the tune. IIRC, your IAT sensor is part of your MAF....correct?

Edit: just saw where you stated that the IAT indeed IS in the MAF.

HydroStream6

iTrader: (16)

I will try that and see if it makes a difference. Thanks

salemetro

iTrader: (5)

Set the MAF fail freq. to 0 hz. You'll get a p0103 code, but don't worry about it...it's just telling you that the MAF is not being used for calculations. Tune VE. Once VE is dialed in, set MAF fail freq. back to normal....then force the PCM into MAF-only mode.....tune MAF freq vs. AFR error, then re-enable blended MAF/VE running.

joecar

With the MAF failed, there is a transmission max pressure table that mentions the MAF DTC's...

since your IAT is integral with your MAF, that same table also mentions IAT DTC's...

with either of MAF or IAT missing, those DTC's trigger in the max pressure table.

But as salemetro has said, you should have been tuning with IAT connected.

HydroStream6

iTrader: (16)

OK I've been messing around with the MAF plugged in and the failfreq set to zero now. Messed with the VE and all LTFTs are +/- 4 and the STFTs +/- 4 to 5ish. Set the MAF fail freq back to 14khz and again it's lean as hell. LTFTs 20+... Maf isn't leaking. It's really starting to **** me off

salemetro

iTrader: (5)

You need to tune your MAF curve...also, I like to try to get within 1-2% on the VE

HydroStream6

iTrader: (16)

I guess I've lost my touch after not doing this for years. Care to enlighten me a bit on this MAF curve tuning? Thanks for your help

HydroStream6

iTrader: (16)

I think I found it in the stickies. I'll let you know how i make out

salemetro

iTrader: (5)

Basically, you're going to log Commanded AFR vs Actual AFR (AFR Error) vs MAF Frequency. Let's say that you're car is running lean by 10% at 6000hz....in this case, you need in increase the value in your MAF frequency table under 6000hz by 10%. You need to do this for as much of the table as you can possibly hit, while smoothing/interpolating the areas that you're not able to hit. This is the process in it's most simple form. I suggest doing some searching around for some "how-to" write ups.

salemetro

iTrader: (5)

There ya go!