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SVTPerformance's Chain of Restaurants
Tuning À la carte
Idle Issue. Possible Fuel Pump tuning issue.
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<blockquote data-quote="decipha" data-source="post: 15517473" data-attributes="member: 74327"><p>the pump voltage table is only a feed forward as long as its not way out in left field its fine as the ecu saves a corrected kam table (as long as u dont disable it or reset the ecu kam) to maintain target deltaP</p><p></p><p>idle instability are going to be due to 1 of 4 possible causes</p><p></p><p>1) fuel variations, if in closed loop make sure its switching at stoich (some longtubes cant measure stoich at idle) and making small jumps (amplitude), since you have longtubes you need to make sure the correction delay isnt occuring before the o2 sees the adjustment made otherwise itll be trying to hit a moving target causing more idle oscillation</p><p></p><p>2) spark, the ecu throws around spark as a fine adjustment to correct for per cylinder and short term corrections, make sure the spark jumps arent too small that is cant correct and make sure its not too large making it oscillate, idle spark is determined by the feedback torque reserve function which is the target and based on the MBT spark table, the correction rate is the spk_fbs_gain scalar, the stock tq reserve function in the fbgi0 cals are absolute garbage and cause idle instability even on a bone stock cobra</p><p></p><p>3) the isc correction, make sure your not overtaxing the isc valve by making sure the iscdc is below 35% at idle, then check ipsibr and isckam and make sure they result in a sum of 0.0000 or near it, if you hadnt dialed in idle air then id recommend just adjusting the isc multiplier table to get it closer as its the least intrusive and wouldnt require any revamping</p><p></p><p>4) mechanically induced oscillations due to erraric combustion, this could be caused by a leaking fuel injector running one cylinder richer, a misfire causing the hego to report lean and as a result dumping fuel, a vac leak that affects cylinders unproportionately, or even a weak coil, fouled plug, etc.. anything mechanical could even be a wiped lobe on the cam or a leaky valve, exhaust leak, u name it</p></blockquote><p></p>
[QUOTE="decipha, post: 15517473, member: 74327"] the pump voltage table is only a feed forward as long as its not way out in left field its fine as the ecu saves a corrected kam table (as long as u dont disable it or reset the ecu kam) to maintain target deltaP idle instability are going to be due to 1 of 4 possible causes 1) fuel variations, if in closed loop make sure its switching at stoich (some longtubes cant measure stoich at idle) and making small jumps (amplitude), since you have longtubes you need to make sure the correction delay isnt occuring before the o2 sees the adjustment made otherwise itll be trying to hit a moving target causing more idle oscillation 2) spark, the ecu throws around spark as a fine adjustment to correct for per cylinder and short term corrections, make sure the spark jumps arent too small that is cant correct and make sure its not too large making it oscillate, idle spark is determined by the feedback torque reserve function which is the target and based on the MBT spark table, the correction rate is the spk_fbs_gain scalar, the stock tq reserve function in the fbgi0 cals are absolute garbage and cause idle instability even on a bone stock cobra 3) the isc correction, make sure your not overtaxing the isc valve by making sure the iscdc is below 35% at idle, then check ipsibr and isckam and make sure they result in a sum of 0.0000 or near it, if you hadnt dialed in idle air then id recommend just adjusting the isc multiplier table to get it closer as its the least intrusive and wouldnt require any revamping 4) mechanically induced oscillations due to erraric combustion, this could be caused by a leaking fuel injector running one cylinder richer, a misfire causing the hego to report lean and as a result dumping fuel, a vac leak that affects cylinders unproportionately, or even a weak coil, fouled plug, etc.. anything mechanical could even be a wiped lobe on the cam or a leaky valve, exhaust leak, u name it [/QUOTE]
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SVTPerformance's Chain of Restaurants
Tuning À la carte
Idle Issue. Possible Fuel Pump tuning issue.
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