idle problem

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b.r.i.a.n.
Posts: 14
Joined: Sun Mar 21, 2010 9:57 am
Location: south florida

idle problem

Post by b.r.i.a.n. »

hello. i had a problem yesterday with the idle on a car i was working on. the afr's were fluctuating and wouldn't stay stable.

i couldn't figure out what it was. i'm attaching a datalog of the car idling for 2 minutes. any help is appreciated.
Attachments
anthony's idle.fpdl
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2003 Civic Si - 241 whp/166 tq - all motor - sold
2002 S2000 - 234 whp/155 tq - e85 powered :D
2006 TSX - daily driver
soxfan143
Posts: 216
Joined: Mon Nov 12, 2007 5:09 pm
Location: lynnfield MA

Post by soxfan143 »

Post the cal. I was having a similar issue but not as pronounced and to fix it you need to reindex the idle columns to keep the ECU from having to interpolate so much at idle. My idle is smooth as glass with ID 1000cc injectors and 70psi base fuel pressure.
BV1
Posts: 28
Joined: Sun Aug 23, 2009 9:13 am

Post by BV1 »

soxfan143 wrote:Post the cal. I was having a similar issue but not as pronounced and to fix it you need to reindex the idle columns to keep the ECU from having to interpolate so much at idle. My idle is smooth as glass with ID 1000cc injectors and 70psi base fuel pressure.
I reduced interpolation with good results as well too. You may be aware, but just sharing for others to keep in mind that MAF shines in idle situations but the decreased resolution of MAP is more apparent, as in its normal for a MAP based car to have more fluctuation in IPW at idle due oscillations in the feedback system due to the MAP resolution. I say more relatively... when compared to the MAF sensor windchill affect which is increasingly accurate for smaller air flow amounts. 2-3 grams/second at idle says more to the ECU with regards to IPW then say -21.7psi.

Also the idle appears to be partly controlled by ignition advance/retard which also seems to have a mild affect on AFR due to charge combustion time, which adds to the seemingly increased oscillation.

I often see my WB02 reading 14.7 rock stable at cruise, but 14.4-14.7 at idle.

Steve
Student: There's no replacement for displacement!
Teacher: HP is essentially Torque * RPM.
Student: <?>
Teacher: So, technically there is no replacement for RPM either.
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