big cammed c5 idle issue
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Instructor
Joined: Aug 2014
Posts: 246
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big cammed c5 idle issue
I am running a SNS stage 3 235/243 .631/.610 with a ported ls2 intake, ported ls2 tb, longtubes, cattless x pipe, mildly hand ported 243 heads. 99% of my tune is good, it will drive part throttle in 6th gear at 45mph with no bucking, wot is good, it even comes back to idle without searching or any of that crap. The only thing that is bugging me is the actual idle, I want a nice even steady chop but it wont do it. It will start to idle nice and steady then it will sound like its fighting with itself and the engine and car will start shaking. The idle dosent search, it stays right around 900 rpm and my spark is steady at 25/26*. Iv tried close loop idle at 14.7 but my o2 sensors are very erratic so i thought the 17* of overlap was causing the o2s to throw my idle off so I tried open loop and leaned it out to 16.3 which it seemed to like but it still kicks into this quick chop/struggle and shakes the car. Im not sure what to do with it anymore. Any body have some suggestions?
My tune is attached.
My tune is attached.
Last edited by hodge9386; Nov 21, 2015 at 10:02 PM.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Saying that it idles better in Open Loop when you command a LEANER AFR tells me that in Closed Loop you need MORE "Idle Airflow " In EFILIVE it's called "desired airflow" not sure what the table is called in HP----It is scaled in 2 tables---In gear and P/N--
and then by engine coolant temp-----
ADDING a % to both will add idle airflow both in CL and OL----I would start with at least a 20-25% increase across the board--
If you go too far--you will get the opposite affect ---a hanging idle--then simply start taking some % out--
and then by engine coolant temp-----
ADDING a % to both will add idle airflow both in CL and OL----I would start with at least a 20-25% increase across the board--
If you go too far--you will get the opposite affect ---a hanging idle--then simply start taking some % out--
