DIY Reference Guide to OBD1 Conversions - Question and Anwer Thread

So can anybody write a "step by step" of how to get the car to idle properly without doing the IACV swap? I'm in need of a new ECU and wanna know how to get OBDI to run correctly before i go about doing it. Thanks in advance.

So nobody knows eh?

I'm in Canada for the Holidays, so I have very limited internet access, but I'll give you the skinny real quick...

You need to pull one of the three wires from the IACV plug and ground it to 'lock' it closed. I want to say it was the reference signal wire, but I can't remember the color off the top of my head. This locks the 3-wire IACV shut so no air passes through, and made my car idle around 460rpm (amazing it can do that).

Now you'll have to manually adjust the idle up to par. The idle air bleed screw is for minor adjustments so it won't help you much. You need to loosen the throttle stop screw on the bottom of the throttle body. It's below the throttle rotors. It's setup like the valve adjust screws, with a nut to hold the screw in place. I think it's an 8mm, but anyway, loosen the nut, then use a flatblade to turn the throttle stop screw until you reach a nice rpm. I set mine a little high (~970rpm) because the A/C will bog it down a few hundred now that you've disabled the IACV. If you set the idle too high, you'll run into the bouncing idle because the ECU will cut fuel to slow the idle. Tighten her back up and you're good to go.

If your tuning software allows, you can disable the CEL for the IACV so it's not an annoyance. Sorry to be so brief, but this is the best I can do from memory without any references or my car to look at.

First post updated with info on launch control.

Hey Jason, let me get this correct once and for all. By the adjustments you described in post #23, you can use the 3wire IACV and not even worry about blacktraxx plate or swapping a 2wire one in? Then adjust the idle manually, and later have it tuned out correct?
(confirm)

At this point you can just plug in OBD1 ECU and conversion harness, then do post #23 trick, and it will work fine?
(confirm)

May you please take a look as to which wire needs to be grounded out (Resistance wire? Color? Placement on plug [left/right/middle]?) to complete this modification.
(confirm)

I would appreciate your response greatly!!!

- Nikita

OK so we did the stunt again but with a chipped P28 from my friends B16.....the idle was stable but was sputtering....my guess is.....since the P28 was chipped with a basemap specifically for my friends SI, the amount of fuel being sent to the engine wasn't enuff to keep it riding smooth SO i can personally vouch that the technique works WITHOUT having to purchase an OBD1 Iacv, all u ahve to do is ground the third cable which my friend did for me and it will idle correctly....i will be purchasing a P28 and chipping it and having a basemap of a F23 in it and will run it and see how she rides and post the update on here....i gve mad props to the guy who wrote this thread up

which wires do you have to repin on the ecu if you go from a 3wire to 2wire iacv?