so ive found and installed a disconnectable connector for the ignition bypass wire, which as im understanding is the tan with black tracer from computer to ignition module. however, it does nothing when i disconnect it. warm or cold, no change. it fires up great, idles super high (around 2000 rpm) for a few moments, then the iac seems to attempt to bring it down to an idle, and instead it seems to drop too far, like 400 rpms or a little less, to the point where it nearly dies, but struggles a bit til it throws it back up to 2000 rpms or so, and it repeats that about 4 or 5 times and then it will go down to around 1400 or 1500 and stay there til it warms up more. and when it idles close to normal, the timing light shows 0 degrees, which is where it should be. it just acts like its too advanced to handle it so it idles way higher again. GRRR. ive even bypassed both mechanical and vacuum advance at this point. im lost again.
If you have 0* timing with the bypass wire disconnected, that is good. That is what you're looking for. After turning off the engine, reconnecting the bypass, starting again, are the symptoms you describe still happening?
I have copied and pasted the IAC reset and minimum idle speed and the TPS voltage setting procedures from the Injection tech forum found on binderplanet.com. I would follow those procedures before doing much else, It will result in a lot less heartburn, I know, I been there...
2. IAC reset/min idle speed- This sets the throttle plate on the throttle body to a specific rpm. I recommend about 500 rpm for most engines. A little common sense goes a long way. Obviously a cold engine will not properly idle when you disconnect the idle control. So ensure your engine is up to temp prior to setting the min idle speed.
Procedures- Go to sheet 7 of the pinout diagrams. At the top is the ALDL connector. You need to put a jumper between pins A and B of the connector. These are pins A9(wht/blk) and A12 (blk/wht) on the ECM. This puts the ECM into aldl mode. Turn the key on (not start) and the IAC should drive completely closed. You will normally hear a buzzing from the IAC. If you have the winaldl up and running on your laptop, you should see the IAC went from 145 to 0. Now unplug the IAC connector. turn the key off. Remove jumper. Start motor. If the idle is too low you may have to keep it running. On the front drivers side of the throttle body is the adjustment screw. It may be behind a silver plug. If so just use a nail or punch to poke it and remove it. Then use a #20 torx bit to adjust the idle speed to at least 100 rpm less then your warm idle speed. if 600 then set to 500 rpm. You are looking for the lowest consistant idle your motor will do. When set, turn off motor and reconnect the IAC. I try to keep the IAC count to about 40 with the motor warm and idling. If the counts drop to 0 then the IAC can no longer adjust the idle down.
This is a good time to verify the operation of the IAC. When the jumper is in and the key is on the IAC is driven closed. So while it is idling to set min rpm put a finger over the IAC port just above the IAC. There should be no air being sucked in and you should be able to see the pintle on the IAC.
When the IAC is connected and operating there should be a small amount of air being sucked in the port at idle and should increase as you apply some throttle.
3. TPS-throttle position sensor. With the idle set, you need to now set the TPS. This need to be set to about .54V. I normally shoot for about .6V.
The TPS is on the passengers side and will have 2 screws holding it on. The factory TPS will not have much room in the holes for adjustments so I use a drill bit or file to elongate the holes as needed. To adjust, just loosen the screws and trist the TPS. You can monitor the voltage on Pin B of the connector with the key on or at pin C13 of the ECM. You can also see it on the sensors tab of winaldl!! Anything away from .54V will also show as a percent of throttle. Such as .2 percent or 1.7 percent...depending on how far from .54 you are. I try to keep the idle setting to within 1 percent.
This is also a good time to check your TPS. Once it is set, just watch the voltage as you open the throttle. you should see a steady rise in voltage up to about 4.5-5V at WOT-wide open throttle. If it jumps up and down or skips some then you may want to replace it.
A big thanks to Billusn-1 at Binderplanet.com for maintaining this information.
Jon In Tucson