Engine Idle Speed Control Issues
-
m-barans
- Posts: 88
- Joined: 2021 Feb 16, 23:09
- Location: Lafayette, Oregon US
- Vehicle Information: 2003 Mercury Marauder 300A with new stock bore IRON 4.6 block, Manley crank, Manley H-tuff h-beam rods, CP pistons with stainless rings, ARP head studs, GT500 lash adjusters and rollers, D series cylinder heads, VMP GEN3R 2.65 L TVS blower, 80 lb/hr FRPP Siemens Deka injectors, HPX slot 100mm MAF, coyote mustang fuel pump with Holley 60 psi filter/regulator return at pump, Stainless works long tube headers and complete exhaust, Moates quarter horse and TunerPro RT with support from Decipha, RZASA strategy.
2001 Ford Lightning SVT F-150 stock engine w/ inlet ported M112, GT500 rollers, ARP head studs, metco quick change upper pulley with stock sized upper, K&N intake system, bassani SS exhaust system from the stock manifold flanges back. 4x4 trans oil pan. SSBC big brakes 14” up front. Work/Street truck. My “next to build” with trick flow heads (before extinction) with h-beams & cobra jet crank (sitting in tool box) and proper pistons. Next up after the marauder is dialed in.
Engine Idle Speed Control Issues
Symptoms: racing idle after executing a start, then sometimes surging before settling down to a “normal” idle speed. During low vehicle speed tip in’s, rpms hang for awhile before rapid fall off. With the A/C adder this magnifies this behavior and car basically accelerates on its own with a/c on. On tip in off of idle speed from stops there is almost like a momentary fall off in rpm (delay) before rapidly accelerating. I haven’t made any changes to the calibration related to the Idle speed control or any spark adjustments. I have a new IAC, factory marauder throttle body on the cobra Eaton s/c setup. At warm stable idle ISCDTY is approximately 0.45 and DESMAF is negative at approximately -0.28. Engine speed is approx 650 rpm. SPK actual is approx 15-20. Engine stalls when unplugging IAC valve. Something seems off. What’s the recommended process? I’ve read that a desired target for IAC duty cycle is 25%. Do I need to perform the mechanical throttle control mod in this case?
-
decipha
- Posts: 5033
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Engine Idle Speed Control Issues
you need to set the throttle stop correctly, obviously it needs to be opened a touch
then dial in the isc multiplier table and then dashpot
then dial in the isc multiplier table and then dashpot
-
m-barans
- Posts: 88
- Joined: 2021 Feb 16, 23:09
- Location: Lafayette, Oregon US
- Vehicle Information: 2003 Mercury Marauder 300A with new stock bore IRON 4.6 block, Manley crank, Manley H-tuff h-beam rods, CP pistons with stainless rings, ARP head studs, GT500 lash adjusters and rollers, D series cylinder heads, VMP GEN3R 2.65 L TVS blower, 80 lb/hr FRPP Siemens Deka injectors, HPX slot 100mm MAF, coyote mustang fuel pump with Holley 60 psi filter/regulator return at pump, Stainless works long tube headers and complete exhaust, Moates quarter horse and TunerPro RT with support from Decipha, RZASA strategy.
2001 Ford Lightning SVT F-150 stock engine w/ inlet ported M112, GT500 rollers, ARP head studs, metco quick change upper pulley with stock sized upper, K&N intake system, bassani SS exhaust system from the stock manifold flanges back. 4x4 trans oil pan. SSBC big brakes 14” up front. Work/Street truck. My “next to build” with trick flow heads (before extinction) with h-beams & cobra jet crank (sitting in tool box) and proper pistons. Next up after the marauder is dialed in.
Re: Engine Idle Speed Control Issues
I performed adjustment to the throttle blade stop and have it idling with an ISC duty cycle of 0.25. I will read the write up and work on dialing the multiplier and then dashpot in. Thanks
-
m-barans
- Posts: 88
- Joined: 2021 Feb 16, 23:09
- Location: Lafayette, Oregon US
- Vehicle Information: 2003 Mercury Marauder 300A with new stock bore IRON 4.6 block, Manley crank, Manley H-tuff h-beam rods, CP pistons with stainless rings, ARP head studs, GT500 lash adjusters and rollers, D series cylinder heads, VMP GEN3R 2.65 L TVS blower, 80 lb/hr FRPP Siemens Deka injectors, HPX slot 100mm MAF, coyote mustang fuel pump with Holley 60 psi filter/regulator return at pump, Stainless works long tube headers and complete exhaust, Moates quarter horse and TunerPro RT with support from Decipha, RZASA strategy.
2001 Ford Lightning SVT F-150 stock engine w/ inlet ported M112, GT500 rollers, ARP head studs, metco quick change upper pulley with stock sized upper, K&N intake system, bassani SS exhaust system from the stock manifold flanges back. 4x4 trans oil pan. SSBC big brakes 14” up front. Work/Street truck. My “next to build” with trick flow heads (before extinction) with h-beams & cobra jet crank (sitting in tool box) and proper pistons. Next up after the marauder is dialed in.
Re: Engine Idle Speed Control Issues
Should I just remove about .15 from the values in the cells in the ISC multiplier table and see how it responds? What’s the recommended method for correcting the ISC multiplier function?
-
decipha
- Posts: 5033
- Joined: 2021 Feb 15, 12:23
- Location: Metairie, LA
- Vehicle Information: Work Truck
'19 F-150 3.3L
Re: Engine Idle Speed Control Issues
no you first have to get the throttle body set correctly then adjust the isc multiplier table to keep the idle air correction as close to 0 as you can.
-
m-barans
- Posts: 88
- Joined: 2021 Feb 16, 23:09
- Location: Lafayette, Oregon US
- Vehicle Information: 2003 Mercury Marauder 300A with new stock bore IRON 4.6 block, Manley crank, Manley H-tuff h-beam rods, CP pistons with stainless rings, ARP head studs, GT500 lash adjusters and rollers, D series cylinder heads, VMP GEN3R 2.65 L TVS blower, 80 lb/hr FRPP Siemens Deka injectors, HPX slot 100mm MAF, coyote mustang fuel pump with Holley 60 psi filter/regulator return at pump, Stainless works long tube headers and complete exhaust, Moates quarter horse and TunerPro RT with support from Decipha, RZASA strategy.
2001 Ford Lightning SVT F-150 stock engine w/ inlet ported M112, GT500 rollers, ARP head studs, metco quick change upper pulley with stock sized upper, K&N intake system, bassani SS exhaust system from the stock manifold flanges back. 4x4 trans oil pan. SSBC big brakes 14” up front. Work/Street truck. My “next to build” with trick flow heads (before extinction) with h-beams & cobra jet crank (sitting in tool box) and proper pistons. Next up after the marauder is dialed in.
Re: Engine Idle Speed Control Issues
Update: I set the throttle blade correctly. Then I had so make some changes to the mas air adders for a/c as fords values were bunk. I got it running more seamlessly during those compressor clutch engagements. I’m starting to understand how some stock functions were “calibrated” so inadequately.