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Gentlemen, as you can see I’m a newbe to your site and also to the TBI world. And I hope this long post is not too much to give at first try.
I have recently picked up a TBI w/harness and 16168625 ECU, from a 1993 GMC Sierra 4.3 L V6 with auto transmission. And have installed it on a Toyota 4.2 L inline six with manual transmission. For the most part everything works very well as there is a lot of information about this upgrade. I am using a new O2 sensor (normally runs at about 750 – 800 mV, but at times drops to 0) installed about 3 inches below the exhaust collector, new IAC unit and rebuilt injectors. I have set the IAC per instructions (now about 10 – 11 counts viewed on TunerPro RT @ 500 RPM) from your site, as well as checked the TPS. Timing is set at “0” degrees with the “signal bypass” wire disconnected.
The problem I have encountered is with idle control. I am using a modified Toyota electronic distributor (also have a DUI distributor on order) and it is connected to the GM ignition module. I also have an aftermarket 2 pulse VSS (not used for speedometer, EGR or carbon canister vent) connected on the transfer case output of the speedometer cable, DIRECTLY (not using a VSS buffer) to the 16168625 ECU where the VSS buffer signal normally connects.
At a cold or first start of the day, with the “signal bypass” wire connected, the engine will idle up to about 750 RPM and slowly decrease to about 500 RPM as temperature becomes normal. With normal operating temperature, the idle will surge between 500 – 1200 RPM and sometimes stalls out. If I disconnect the “signal bypass” wire, the idle will settle at 500 RPM and runs very smooth, but with some “popping” from the exhaust. If I do a cold start with the “signal bypass” wire disconnected, the engine will not idle up, but will hold at 500 RPM.
With TunerPro RT connected, I get no signal from the VSS at any running/driving speed/RPM. I read on your site and elsewhere that the VSS should be a 40 pulse type, but am not sure if it makes a difference as I am not using a VSS buffer.
How can I connect the VSS (or which one for that matter) so the ECU can see it??? And would you think this would cure the idle surge problem???
Thanks, Jerry D.
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