car shutting off with Maf tune

[LETZRIDE]

In my car I have been running a VE tune for the past couple of years, but would like to move back to a MAF tune. Ive picked up an LT1 MAF and installed it on the car.

So far I have been tuning cruise and havent gotten the car over 6000hz. Fueling is pretty good, I got it pretty close to 14.7ish under light throttle conditions, the problem is, when I let off the throttle to come to a stop, the car dies out and shuts off unless I two foot the brake and gas to keep it running.

If I flash back to the VE tune, the car acts perfectly fine...did I miss something?

Ive attached the MAF tune as well as two scans that end in the car killing itself when coming to a stop. It does this every time unless I two foot.


Here is a link to the Hp tuners thread with my tune/scans

http://www.hptuners.com/forum/showth...238#post328238

[thebeewantsboost]

Re: car shutting off with Maf tune

i remember having that problem when my maf tune was off. i don't remember what it was specifically

[LETZRIDE]

Re: car shutting off with Maf tune

I wanna guess and say it might have something to do with AE or DE parameters. My guess is that the car is going way rich for a split instant (that the wideband doesn't even see) and it snuffs out the spark.

Reason I say this is because the car just chokes and dies, then is hard to start up, you have to use the throttle to get it going again. When you do this a puff of smoke comes out of the exhaust and it fires itself back up.

When I look at the command AFR just before the car dies it seems to be dropping in AFR command. I.e it starts going from 14.7 to 14.0, to 13.5, etc etc. You just see the command drop

[Blizzard242]

Re: car shutting off with Maf tune

I'm at work so I can't see your scans right now. I had a similar issue before though.. Still not positive on what caused it but I'm assuming it was because I was trying to tune my cruise and idle with my wideband. I may or may not had exhaust leaks that were throwing off my tune, but have you tried tuning idle/cruise with your narrowbands? I heard that was the way to go since the narrowbands are way more accurate at stoich than a wideband. Ehh.. Your commanded is dropping though.. so my whole post maybe irrelevant.

I still need to do this myself, I just leaned up my maf table until it ran well at idle and the wideband looked good-it still has funny drops in the afr though.

[LETZRIDE]

Re: car shutting off with Maf tune

I dunno, but I just tried reverting back to another tune from 2009 that was good. I only swapped my trans tables and tried to start from scratch...same issue.

I dunno what it could be at all now. 1 thought I did have is that the new maf is connected to my filter directly behind the headlight...could this be an issue?

[Blizzard242]

Re: car shutting off with Maf tune

Got an air straightener/screen on the maf?

[LETZRIDE]

Re: car shutting off with Maf tune

no straight pipe, only the maf screen, then maf

[Blizzard242]

Re: car shutting off with Maf tune

Hah, I guess that's a yes.

Is that MAF mounted differently than where it normally would be? I'm reaching here now..

[LETZRIDE]

Re: car shutting off with Maf tune

I dont know where it is mounted for the v8's, but compared to our v6's yes.

Another thought his me. We have voltage vs injector tables. Right now even with my VE table, when I come to a stop I get a voltage drop down to around 10.xx. My car as it sits now gets much quieter than its normal rumbly self.

I wonder if the voltage table comes into play only when the MAF is not set to fail, and throws the table way off due to dropping voltage and the car just stalls out as a result?

What is the best way to modify these tables? or do you think that could be the issue?

[LETZRIDE]

Re: car shutting off with Maf tune

More information on the issue:

The car dies when you go forward even under 1-4% light throttle then hit the brake to stop. At this point the rpms dip down and the car chokes out and dies.
- The car does this regardless of being in open/closed loop
- idle maf calibration is now no more than 6% off in the relative HZ columns
- I dont believe AFR/rich/lean conditions to be the cause- in the scan you will see at teh moment the car dies, afr is as follows: 1054rpm- 13.99afr; 864 rpm- 14.11afr; 702rpm- 14.14afr; 604rpm- 14.08afr; 527rpm - 14.42afr; 431rpm- 14.94 afr and all the way down to 233rpm is at 14.64 afr.

So it's not a case of the car being wayy too lean or too rich when it is choking out...so what's the issue here? Like I said, I flash my VE tune back in and the car runs beautifully with the exception of the voltage dip I get while coming to a stop (which also happens with teh maf tune) but has been happening forever and is common.

whats the deal here guys? Im beyond stumped. I even tried making the voltage offset 1.0000 across the board- Nothing.

I've now posted my new updated tune, scan and cfg file on hp tuners



http://www.hptuners.com/forum/showth...567#post328567

[alex553]

Re: car shutting off with Maf tune

Pictures of your set up?

[LETZRIDE]

Re: car shutting off with Maf tune

Pictures of your set up?

Here

[alex553]

Re: car shutting off with Maf tune

I was experiencing the car dying at stops when my iac was bad but since yours runs fine in speed density I don't think that's it.

[LETZRIDE]

Re: car shutting off with Maf tune

just got it figured out. The revised tune overkill sent me seems to fix the issue. I'll update when I actually learn why those changes actually made it work.

edit: I also replaced my IAC awhile back..maybe 2 years ago

[thebeewantsboost]

Re: car shutting off with Maf tune

any news?