Tuning MAF - Idle hunting leads to stalling

My car is a C5 Z06 with ported heads and 231/236 camshaft. Previous to my clutch job this winter the car was running great. I noticed the fuel trims needed some work so I tuned the VE table, and now I am working on the MAF. The WOT zone of the MAF needs work, but that's another day.

The car idles in the driveway fine, but dips below idle when you rev it. Then hunts and recovers. When I'm driving the car it's another story, hunts badly, idle swings, and then it will stall if you don't assist it with the gas.

I have attached my tune, config, log. Does this seem to be a RAF issue? I ran the russ k idle config last year to get these numbers.

When both VE/MAF are enabled it drives fine, hunts occasionally.

Looking for any pointers or help

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In the editor see (Engine) (Spark) (Advance) (Idle Spark Advance) play with bumping the timing on both drive and park in the 0-1,200 or so rpm area, what i did was took the timing from 1,200-1,600rpm areas and populated all the way over to 0. That fixed my hunting problem, but there are other ways to do it, and or combinations..

Though im not tuning my maf and am only running a gm hotcam, thought it might could work, and be worth it to try or to try a variation of the idea for ya..

Anyways here is my tune file if ya would like, also you can see a video of the idle and rev below.

Hope ya get your maf tuning problem fixed soon :) Peace :) :drivin:

I bumped the timing by 2 degrees as I already had those tables matching my main timing tables. No change.

It wont even idle now, would a vacuum leak cause this? I had no issues when tuning VE, just hard to believe I turn VE off and with the MAF it goes to hell.

Maybe your maf is bad. Turn off your maf and see how it runs. Your maf needs to be smoothed out it looks pretty erratic on its slope. Look how smooth Monty's maf is.

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Originally Posted by gagliano7

Maybe your maf is bad. Turn off your maf and see how it runs. Your maf needs to be smoothed out it looks pretty erratic on its slope. Look how smooth Monty's maf is.

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Yea the slope def needs to be smoothed, I was putting that off until I get the idle fixed. When running with the MAF off the car runs great, no hunting or stalling. I haven't physically touched the maf and it was running fine last year. I am more inclined to think I f'ed something up, opposed to the maf going bad but who knows!

the problem is in your tune. look in my profile for threads I started. I had the same problem and was able to fix it. It could be several things but these DBW cars are not easy.

Try this for fun. If it idles too high while moving, back some items down.
The MAF doesn't work well at low RPM. I only go MAF only for a bit to dial it in and for low RPM, I use VCM controls to push the RPM lower and lower to populate those cells. I do the same with the VE for low RPM and if it's a 6-speed, I will lug the car with the clutch to load it to achieve good values.

If your airflow is good with both tables active, probably fueling causing your issues.

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Originally Posted by blownbluez06

Try this for fun. If it idles too high while moving, back some items down.
The MAF doesn't work well at low RPM. I only go MAF only for a bit to dial it in and for low RPM, I use VCM controls to push the RPM lower and lower to populate those cells. I do the same with the VE for low RPM and if it's a 6-speed, I will lug the car with the clutch to load it to achieve good values.

If your airflow is good with both tables active, probably fueling causing your issues.

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Thanks Bret - Going to try this sometime soon as I just got back in the country.

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Originally Posted by fstz06

Thanks Bret - Going to try this sometime soon as I just got back in the country.

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I flashed the computer with the tune from Bret, I am able to drive it and log. I noticed that the MAF calibration from right above idle to around 1500 rpm is horribly off. Already it has gotten better with smoothing the maf table and of course getting the correct MAF values in place. Going to do some more driving tonight and get the MAF table completed, then see where I am at. The TC/TF are a bit to much but those will be dealt with after the MAF is happy.

I'll post back in a day or so :cool:

Attached is another log from my driving today, and tune modified after drive. MAF is getting more and more dialed in, 1100-1200 needs some more work due to them still being off. Still getting some of the idle hunting but def not as bad.

My MAF curve is getting better looking, but if anyone wants to look at the log and point out anything they see wrong I would appreciate it. Shooting for one more drive and then trying to get the TC/TF hanging down a bit.

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where is your B2S1O2?

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Originally Posted by fullthrottle

where is your B2S1O2?

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Using my config both O2s (Front) are shown. For some reason the logger doesn't allow me to log my non SAE passenger side O2, so I had to use SAE. Really odd if you ask me.

I did some more work and finished up the MAF part throttle tuning. No more hunting, just too much TC but that's going to be handled in a bit.

with such a combination, your killing your self in time. tune your car SD and you will be much happier and smoother.

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Originally Posted by SultanHassanMasTuning

with such a combination, your killing your self in time. tune your car SD and you will be much happier and smoother.

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haha yea I have been hearing that a lot lately, just need to learn more about 1 bar sd tunes

Brett gave you some good advice to get those lower cells in the MAF table dialed in. Turn off you under/over speed idle timing tables while doing that, as they are masking the problem. I noticed when the dips are occurring the MAF cell above where you are idling appears to go quite rich, that with the timing failing might be aggravating the condition.

You might want to try some changes in your over/under speed timing tables as well. Your cam will never idle perfectly so trying to correct in those low rpm cells sets you up for over correcting adding to the oscillation. :)