Idle problems

Anything about Ford EEC tuning. TwEECer and Moates questions dominate, but there's some SCT and OBD-II knowledge too.

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Gear Head
Posts: 22
Joined: Thu Feb 11, 2016 5:10 pm

Idle problems

Post by Streetstallion » Mon Apr 08, 2019 5:30 pm

When I crank my engine from a cold start, it struggles badly and takes forever to idle on its own and when it does, the idle just rolls up and down and then stalls. When I try to crank it back up, I have to hold the throttle open to get it to start up again, like its flooded. I've pulled KOER test and the only code I get is (13) ISC/IAC motor, AIR bypass not controlling idle properly...generally idle too high) but, my idle is set at 850. I've tested all connections and they are good and I'm getting the proper voltage. I've changed the ISC/IAC 3 times with no good results.

What could be causing this??? I'm confused!!! Its also tuned with Quarterhorse.These are my mods.....

FYI: These are my mods...

- N/A 351, bored .030 over..10.6:1 Compression
- Trickflow R intake
-Canfield heads (29-450-58-0)
-Accufab 75mm TB
- 95mm PMAS slotted MAF (MH95B-3000)
- 4” Anderson powerpipe
- 42lb Ford injectors
-Harland Sharp 1.6 rockers
-Compcams 35-518-8, 555/565 lift
- DSS GSX forged pistons
- Accufab adjustable fuel pressure regulator) set at 40psi
- Walbro 255lph fuel pump
-Crane Fireball Ignition box
-Fireball coil...
-Autolite plugs, gapped to 0.45
89 Mustang GT, A9L ECM controlled by Moates Quarterhorse, N/A 351w bored .030 over, Keith Black 11.1 compression pistons, Canton windage tray and 7 qt oil pan, Edelbrock Performer RPM intake, Canfield Stage II heads, TF 75mm TB, Pro-M 75mm MAF, 36lb EV6 injectors, AEM wideband, Ford Motorsport 1.6 RR, Compcam 35-518-8 (555/565 lift), BBK longtubes w/x-pipe, Ford Racing Z T5 tranny and 3.55 gears out back.

Gear Head
Posts: 11
Joined: Mon Dec 22, 2014 4:49 am

Re: Idle problems

Post by FoMoCo17 » Wed Sep 25, 2019 9:51 pm

From what I know, you get a code 12 or code 13 from too low or high an idle set screw setting. You mentioned your getting the code 13 which I believe like you said is too high of an idle. This tells me that the idle is too high. Either it’s by the set screw or the IAC is always open. If set screw is too far open, I’d bet your IAC is not opening. Thus, what you should do is log your duty cycle of IAC and get somewhere between 30-35% on a hot engine at idle. To get this, you probably have to back off your idle set screw until the IAC duty cycle rises to that 30-35%. Then, the car probably will not stall out. If you log IAC and its and by chance it’s fully open n duty cycle is 100% (which I doubt it will be, then I’d imagine you need to open throttle blade screw more and then get duty cycle to that 30-35% range again. Think you’ll find the IAC is closer to “0” as in first scenario once logged. Changing the IAC 3 times was not the answer obviously, a wiring or signaling problem could also be the problem so that needs to be checked if the above does not solve your problem.

If all else fails, and my memory serves me correctly, I believe Decipha did a write-up on a mechanical throttle body adjustment for big cammed engines which may be of interest to you or of interest.
306 Forged Assembly w H Beam Rods and Girdle, Kenne Bell 2.1, E7 Ported Heads & Intake, Kenne Bell FMU, 19# Accel Injectors, BBK Fuel Pressure Regulator/Gauge, Stock Cam (+2 degrees), 1.7 Crane Roller Rockers, 60 mm throttle Body, 55 mm MAF w stock sensor, BBK Cold Air Inlet, BBK Shorty Headers, BBK H-pipe, Autolite 24 Plugs, EGR & Thermactor Enabled, 2 1/2 MagnaFlow SS, built AOD w 2400 Hughes Converter, Flex-a-Lite Cooling Radiator/Module Assy., 130 Amp Alternator

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