MSII, 2.68 code, V3 board with TIP120 mod
IAC was working as designed and had been working great for over a week. I warmed my Jeep this A.M. and the idle droped down to 700, got about 1 mile from home and the idle went to 2500 RPMs.
I understand there is a lot of variables here but is it common for that transistor to short out? Disconnected the IAC and the engine ran fine, logged into the ECU with MegaTune and changed the tables around (-40 to 160 and back) but there is no change. The IAC does not seem to be responding.
Some threads on this board explain that the frequency could cause it to stick open (pretty sure mine is set to 80)??
Thanks.
Ford IAC PWM stuck open
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Ford IAC PWM stuck open
84 Jeep w/393 Ford, MSII, truck intake, TB, Ford sensors.
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
I did not install the flyback diode, whoops. Looks like I got a voltage spike and it took out the transistor. Next step is to measure the resistance between collector and emmiter. Willing to bet it is shorted though. Hope I bought two when I ordered them from digikey!
84 Jeep w/393 Ford, MSII, truck intake, TB, Ford sensors.
Fixed
Got it fixed, there was a short from the collector to base leg of the transistor down where Q4 was supposed to go. Apparently when I extended the wires they were far enough apart to work but as I drove the rig they vibrated and created the short. I moved the collector wire to the other (towards DB37) end of R39 to have one less wire on Q4.
84 Jeep w/393 Ford, MSII, truck intake, TB, Ford sensors.