North American Turbocoupe Organization



Diode and idle problem
Keith Nubel Offline
Posting Freak
#1
Could a defective diode in the wiring for the idle air control cause an idle problem?

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85.5 TC 5 speed, Ranger Roller cam, 3" exhaust system, manual boost valve, large VAM, SVO PE computer, front mount Motorsport intercooler & sport grille, ported upper and lower intakes,flow matched injectors, ported E6 manifold, 245/45/17 wheels & Tires,140 mph speedo,Motorsport lowering springs, under restoration
1985 TC
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Jeff K Offline
Administrator
#2
Shorted diode will make the IAC inoperative or nearly inop. and could possibly take out the driver in the EEC. Open diode will not really hurt / affect anything. It is just there to protect the EEC from voltage spikes as the IAC dithers, even though the EEc has protection diodes on the I/O circuits to do the same thing. If one lead of the diode is disconnected, it can be checked with a DMM.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 21 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Keith Nubel Offline
Posting Freak
#3
I know they flow current in 1 direction, but how much resistance should it have?
1985 TC
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Jeff K Offline
Administrator
#4
Quote:Originally posted by Keith Nubel:
I know they flow current in 1 direction, but how much resistance should it have?

Put DMM on a high resistance range, like 200K ohms or so. With one polarity, resistance should show infinite (overload, etc, depending on the meter). With the other polarity, should show a few to a few hundred ohms.... all depends on how much voltage the DMM applies during resistance measurements.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 21 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Qwertys Offline
Senior Member
#5
most dmm's have a continuity/diode check. it should tell you either the forward resistance, or voltage required to forward bias the diode.
'85 TC BPV and Ford FMIC
'88 TC Kirban AFPR, Autometer Boost, FP and A/R Gauge, 8.8 to 4.10 rear, Walboro 255lph Fuel pump, Garrett GT3071R T3/T4 Dual Ball bearing Turbo, Custom AWIC.
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