greenbuggy

Few months ago I swapped a 96 T100 3.4 into my 93 Xcab 4x4 manual pickup. Only non-stock item is the cone air filter because I couldn't make the stock T100 airbox fit without cutting my hood. I recently did plugs because it was misfiring, replaced with NGK BKR5EKB-11 (OEM style dual ground plugs). Before the plugs were changed last week I had a hard time with hot restarts if the truck sat for more than a minute (like when getting fuel)

It did have a little bit high idle before and after the swap (1700-1800 RPM). I figured it was due to throttle cable (which I bent and adjusted to fix, and it dropped to 13-1400 RPM) but lately its gotten worse. Hot, its revving up near 2400-2500 RPM,just under 2000 cold. Throttle cable bracket is bottomed out on the idle screw and idle screw is just barely protruding from its boss.

My CEL is on, but for a B1S2 oxygen sensor, which I have not yet modified the exhaust to take (since the 93 never had a post-cat O2 sensor) and is disconnected. Before changing plugs it had a couple misfire codes but that was it.

I sprayed all over my engine compartment looking for vacuum leaks and found nothing. I think if it was actually leaking vacuum I would have gotten a "running lean" code from the ECU. I also cleaned throttle body to make sure plate could close fully, to no avail. I suspect that this is an engine management issue. A couple things I've noticed:
- at rest, TPS reads 12% and at full throttle it only goes up to ~80% according to my Bosch Mastertech scan tool. At full throttle the throttle plate is fully open.
- Engine warm the ECU temp sensor is claiming around 87-89*C
- IAC ratio is ~40% according to scan tool (I don't know what this number means)

Is my TPS just bad? Do Toyota IAC's get dirtied up with carbon like on GM TBI systems? Is there a way to see what position IAC is being commanded to?

SacRunner

This quote is concerning to me, you need to stop thinking of your truck (at least with anything that relates to the engine/exhaust) as a 93 and start thinking of it as a 96. It makes no difference that the 93 only had 1 O2 sensor, the 96 had/has 2, so you will NEED to have both for it to run correctly. I have no idea what the symptoms of it running incorrectly are, but your high idle may be caused by that.

FWIW, my idle is right at 500-600 when warm with a 97 4Runner ECU/motor, so even the 1700-1800 seems high to me.

greenbuggy

The title says its a 93, I didn't avoid installing the rear O2 because it didn't have one when it had that awful 3.0 from the factory, I meant there's no bung for me to attach the rear O2 sensor into or else I would have done it already.

That said, it had a high idle when it was still in the 96 with the rear O2 installed. I very much doubt that Toyota would program the ECU to rev to 2400-2500 RPM when an oxygen sensor goes bad or is disconnected.

SacRunner

I completely understand that the stock exhaust from your 93's 3.0 did not have a port for a second O2 sensor, but you need to add one for the 3.4 ECU to know that the engine and catalytic converter are working correctly; without it, the engine may not run "right" or at the very least, it will just throw a code.

Now, if the T100 had the high idle before the swap, I would start looking at the various sensors and electronics that you swapped over. The first thing I would look at is the IAC (Idle Air Control valve), it could be stuck open, allowing more air into the engine causing the engine to idle up. There are plenty of threads around here documenting how to remove and clean the IAC.

vasinvictor

iTrader: (3)

I plugged my rear 02 sensor is but it's always been zip tied up neatly somewhere. I've only ever thrown an 02 code twice and I just reset it and keep going. FWIW YMMV