RX744CSP

iTrader: (4)

Another stupid question; I'm loaded with them.

My setup's a little weird, I have an S5 TII engine which is allegedly a JDM piece. The FSM says the idle is adjusted via a screw in the IAC motor, basically an air bypass just like a N/A motor only it's not on the intake itself.

My engines (I have two) do not have idle screws in the IAC valves. They are not missing, the holes have never been machined.

The throttle stop screws have no locknuts, just a spring which keeps them from moving on their own, just like olde tyme carburetor idle screws.

The S5 TPS's on these motors look and ohm out exactly like the FSM says but for various reasons I'm using S4 stuff. Yeah, it's a long story. FWIW, the narrow range side of the S5 TPS ohms out exactly like an S4.

So here's the question: turning the idle screw (I assume the way it's built means the stop screw is now the idle speed screw) will change the TPS setting. Does anybody have any info on how to adjust the 'home market' setup, i.e. throttle plate initial gap setting etc?

SpikeDerailed

iTrader: (7)

That JDM models dont have a screw on the idle control valve. To the second part, a picture of what you're talking about would help.

RX744CSP

iTrader: (4)

Since I posted this, a lot of back and forth between this 'idle screw' and the TPS has gotten it to where the idle is about 825 RPM and using a checker light (actually two LED's in the check connector) only one side illuminates. I can run the TPS screw in/out, get both lights to turn on or go off as the FSM says. So that seems to be okay, although I will do the '1 volt at idle' check that I've seen recommended.

But, new problem (and through the search function it seems this is not unusual but there's no real discussion of why this happens): at idle the ignition timing shows full advance when checked on the leading plug on #1. Blipping the throttle does not show advance happening but it does do the momentary retard on throttle closing which according to the FSM and previous NA motor experience is a normal function. The check connector is definitely not grounded when checking the timing and when it is grounded the IAC definitely is out of the picture (I use a small toggle switch, the idle drops way down with electrical load, when the switch is flipped off the same load causes only a momentary idle dip) so it appears to be doing its thing.

If I try to retard the timing to get it to factory spec the engine will run like *** and eventually shut off. I've done all the stuff recommended (make sure it's at full operating temp, set the TPS, made sure there's no vacuum leaks etc but still can't get it to show proper timing.

During all this messing around once (and once only) the timing did show normal and I set it quick so right now my base timing *should* be correct. But shortly afterwards it went right back to the same thing.

TL; DR, right?

SpikeDerailed

iTrader: (7)

Unless you jump the connector to make the ecu lock timing is will play with timing as one of the ways it tries to maintain a decent idle.