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 Post subject: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Tue Nov 21, 2017 12:44 am 
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Joined: Wed Jun 06, 2012 10:11 pm
Posts: 25
I had ceramic coated headers a while back and have been battling with trying to get the tune to behave.

If I scale the MAF with the car hot (such if I had been in slow traffic on a hot day) – I can get the MAF scaled in nicely and the fuel trims close to zero, but when I start the car the next day, my fuel trims are anywhere from -10% to -15% - even when the car has reached operating temperature (colder temperature = runs rich).

OR, if I scale the MAF on a cooler day (still with car at operating temperature, but engine bay not quite as hot)... I can get the fuel trims close to zero, but then the next time I am stuck in slow traffic and the engine bay builds up heat - I see fuel trims of +10 to +15 (hotter temperature = runs lean).

Things I have checked:
1) It's not related to coolant temp, because in both scenarios the car runs fairly consistent coolant temps.
2) My MAF compensation (IAT) tables are zeroed out.
3) My fuel pressure is OK (the gauge does lose a bit when the car is hot, but I've narrowed that down to the fluid filled gauge by cooling it with a cold pack) and seeing the pressure return to normal.
4) My o2 sensor reads accurately (confirmed with a wideband fitted to the car)
5) Battery voltage seems OK when car hot (thought maybe it was effecting latency tables)

Any other ideas?
Kim


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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Tue Nov 21, 2017 3:07 pm 
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RomRaider Donator

Joined: Tue Apr 29, 2014 12:48 am
Posts: 723
I have seen that many times. But in my case it's within the 5%-7% which is acceptable. Try to tune the maf in between the the two readings.

I think it might be related to the fuel temperatures.

Once the ambient temperature gets more low and the air becomes denser it will not be rich and the Mag sensor should adjust.

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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Tue Nov 21, 2017 4:57 pm 
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Experienced

Joined: Thu Dec 18, 2014 6:31 pm
Posts: 698
Location: oregon
What MAF is it? Pictures?

Under MAF scaing there is a compensation for IAT, have you thought about checking that out?

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'03 USDM WRX - EJ205/TD04/FMIC/SD - 2.72 g/rev @ 3950 rpm and 237 g/s @ 6100 rpm


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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Tue Nov 21, 2017 5:26 pm 
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Joined: Thu Aug 03, 2006 10:40 am
Posts: 1901
jon7009 wrote:
Under MAF scaing there is a compensation for IAT, have you thought about checking that out?


kim wrote:
2) My MAF compensation (IAT) tables are zeroed out.


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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Wed Nov 22, 2017 2:49 am 
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Joined: Wed Nov 22, 2006 10:23 pm
Posts: 2428
That seems like a good place to start.

This is what those tables are for, isn't it? :)

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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Wed Nov 22, 2017 2:55 am 
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RomRaider Donator

Joined: Tue Apr 29, 2014 12:48 am
Posts: 723
Actually it's not related to this table on a sunny day IAT would be 30C and the correction and learning would be on the positive side . At sunset IAT would report the same temp 30C but the scaling would be perfectly zero.

And on the begining of the drive on sunny day it's perfectnear zero or or negative.

So IAT table would not resolve this.

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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Wed Nov 22, 2017 7:13 am 
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Experienced

Joined: Thu Dec 18, 2014 6:31 pm
Posts: 698
Location: oregon
primary base enrichment? it's based off ECT, so what difference if any is your coolant temp between the two scenarios?

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'03 USDM WRX - EJ205/TD04/FMIC/SD - 2.72 g/rev @ 3950 rpm and 237 g/s @ 6100 rpm


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 Post subject: Re: Trying to troubleshoot - lean when hot or rich when cold
PostPosted: Wed Nov 22, 2017 7:22 am 
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Joined: Tue Apr 29, 2014 12:48 am
Posts: 723
It's zero above 60C/140F.

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