IAC for 1983 Turbo Coupe? June 25, 2016, 05:13:58 PM I have everything running well on this car except for the annoying stalling when I am off the gas while shifting. I have learned much from searching the forums on the subject. The IAC appears to be the problem. Where can I get one? No problem getting one for 1984 to 88 - but everywhere I look I am informed that those are incompatible with 1983 - although they certainly look similar. Any assistance will be appreciated. Quote Selected
IAC for 1983 Turbo Coupe? Reply #1 – June 28, 2016, 01:20:17 PM Except maybe when cold, if base idle and TPS voltage are set correctly it should not be dieing even if IAC is defective... Base idle is usually 50-75 RPM less than normal idle... Quote Selected
IAC for 1983 Turbo Coupe? Reply #2 – June 28, 2016, 10:49:15 PM Back to the drawing board, it seems.And would this then imply that the IAC is superfluous as long as I warm it up adequately? It will idle if I get off the gas gently - as when coming to a stop. It is only with the foot off the gas shifting (for example) 3rd to 2nd for corner while braking that is essentially just shuts off. No, I am not that skilled to heel and toe all of these. Quote Selected
IAC for 1983 Turbo Coupe? Reply #3 – June 29, 2016, 10:10:47 AM Sounds like it could be IAC but if you bring the idle up to a normal speed it should not stall, at least when warmed up... You can set it 50-100 RPMs high without issue... Also the TPS voltage should be verified after idle is reset...I assume it's been scanned for codes??? Quote Selected
IAC for 1983 Turbo Coupe? Reply #4 – June 29, 2016, 06:44:52 PM Yes, but not by me. Time to get out the voltmeter. After a rather rigorous review of apparently relevant posts I was hoping to try the quick and easy approach first. I am getting the impression that one does not find IACs for 83 TCs and I find no information on the incompatibility with 84 - 88. Perhaps this is why the professional working on it gave up. Thanks. Quote Selected
IAC for 1983 Turbo Coupe? Reply #5 – June 29, 2016, 09:03:23 PM I assume the 83 is like the others. Have you taken it off and tried cleaning the carbon off and put a new gasket on it? Checked the TPS voltage and make sure it is in range? Quote Selected
IAC for 1983 Turbo Coupe? Reply #6 – June 29, 2016, 10:15:52 PM Looking at the EEC wiring diagrams the '83 has a second feed back to computer from the IAC through a 10 ohm resistor... I dunno but possibly you could swap to a '84 computer, do away with the extra wiring and use the newer IAC...You checked over on NATO??? Quote Selected
IAC for 1983 Turbo Coupe? Reply #7 – June 30, 2016, 10:58:44 AM Quote from: TurboCoupe50;455981Looking at the EEC wiring diagrams the '83 has a second feed back to computer from the IAC through a 10 ohm resistor... I dunno but possibly you could swap to a '84 computer, do away with the extra wiring and use the newer IAC...You checked over on NATO???My 83 EVTM doesn't show an extra wire with a resister to the EEC. It looks the same as the 84 EVTM.Check the connector and see if it has more than two wires.Maybe it's a question of whether you have an early or late 83. Quote Selected
IAC for 1983 Turbo Coupe? Reply #8 – June 30, 2016, 12:10:41 PM Quote from: softtouch;455982My 83 EVTM doesn't show an extra wire with a resister to the EEC. It looks the same as the 84 EVTM.Check the connector and see if it has more than two wires.Maybe it's a question of whether you have an early or late 83.I dunno if there is a extra wire as it's possible it's spliced in the harness... The wiring diagram does lead one to believe ther should be a extra wire or resistor connected... No doubt could be early vs late... The 1984 diagram I have doesn't show resistor or any connection back to pin #41... Quote Selected
IAC for 1983 Turbo Coupe? Reply #9 – July 01, 2016, 02:29:20 PM 83redbird:From the 84 Shop Manual:The resistance of the solenoid should be between 7 and 13 ohms.The base part number is 9F715. Rockauto.com list some OEM part numbers that Airtex 4J1014 replaces. You can see several parts numbers with 9F715 there with prefixes and suffixes attached.Check if any of these part numbers match your ISC. (hope yours has a p/n you can read.) Quote Selected
IAC for 1983 Turbo Coupe? Reply #10 – July 01, 2016, 03:56:26 PM TurboCoupe50:As stated before, my 83 EVTM doesn't show EEC pin 41 being used for anything on the 2.3L turbo.But to help clear up the confusion:I have the huge wiring diagrams on 25x12½ inch sheets that I ordered in '84 when I ordered the '84 Shop Manuals.These diagrams are marked as being for '84 but show the 10 ohm resister to pin 41 for the 2.3 turbo that your diagram shows.Anyhoo; the EEC pins 21 & 41 is the circuit that is used on the 3.8L to control the ISC motor. Reversing polarity to the motor to reverse the direction the plunger moves. The 10 ohm resister would limit the max current between pins 21 & 41 to 1.2 amps if one was 12v and the other gnd.Since pin 21 goes directly to the solenoid it is going to be the one controlling whether the solenoid is energizes or not. At least that is how it looks to me.I notice in your diagram the pin 41 circuit is labeled ISC LOS.LOS stands for "Limited Output Strategy" There is a timer in the EEC that is constantly running. The software program must keep resetting this timer before it "times out".If the timer times out, it puts the EEC hardware in LOS mode. The software program is now out of the picture. There are no sensor inputs, the SPOUT wire puts the TFI in the 'jumper is out" state and the TFI controls the ignition at the base timing. The fuel pump is kept on. The injectors are pulsed at a fixed pulse width.I have no idea what pins 21 & 41 are doing in LOS mode.Oh, one more thing, I did read somewhere while researching idle air control that one of it's functions is "dashpot"This should keep it from going instantly to low idle as soon as you take your foot off the gas. Quote Selected
IAC for 1983 Turbo Coupe? Reply #11 – July 02, 2016, 10:19:55 AM Yeah I lifted that '83 diagram from the Probst FI guide, no idea if it's actually accurate... With the 10 ohm resistor shown in the '84 master wiring diagram, appears Ford didn't even know what they were using...I'm familiar with the large wiring diagrams you mentioned, have one for '87 I used when I swapped the 5.0 into mine... Quote Selected
IAC for 1983 Turbo Coupe? Reply #12 – July 04, 2016, 11:12:16 PM Quote from: softtouch;456007TurboCoupe50:......Oh, one more thing, I did read somewhere while researching idle air control that one of it's functions is "dashpot"This should keep it from going instantly to low idle as soon as you take your foot off the gas."Dashpot" is the first thing that came to mind when I read the description of the problem. Quote Selected
IAC for 1983 Turbo Coupe? Reply #13 – July 28, 2016, 06:10:42 PM Which brand is the best Air Tex or Standard for a 1986 Cougar IAC? Quote Selected
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