Setting TPS/Idle/Throttlebody AT THA SAME DAMN TIME

[cbh148]

My engine previously had all the idle control gadgets removed, but I've put them back on.

This means that the throttlebody stopper screws have been monkeyed with since they were used to set idle. That goes for the throttle cable mount too. Playing with the idle screw makes a change sometimes, then 15 seconds later it won't. Go figure. Unplugging the AAC valve makes a difference in idle sometimes, but then 15 seconds later it won't. Wtf.

As for setting the TPS, I just now swapped over to a CA18 TPS from my KA24DE model (which didn't have the Idle Switch socket). I tried to set the TPS with both methods -- resistance and voltage. It seems like when I'm hunting for the 1000 ohm spot for off-throttle, it will randomly jump way up. I can find the sweet spot, then open the throttlebody and let it rest again, and it reads something different. Same goes for testing voltage. I can set it to .5v, then open the throttle and close it (with the TPS locked in place) and now it's resting at 2.8v. Wtf.

With 5+ different variables to play with, it feels like I'm trying to pick a combination lock. Any advice on how to get that super smooth OEM fresh-from-the-dealership style idle? I've looked through the FSM and it doesn't account for s***-head previous owners playing with all the settings.

Also, I've got like 2 extra AAC valves and Air Regulators to try out.

[youtube]http://www.youtube.com/watch?v=RYpaRu7ZcJk[/youtube]

[Buddyworm]

Your Idle Air Control Valve is trying to compensate for your adjustments on the throttle body/cable. The reason your unplugging the AAC or adjusting the throttlebody doesn't make lasting changes is because the ECU is programmed with a target idle RPM and will "chase" that target by using the IACV to adjust airflow into the manifold.

With the car off unplug your IACV, set your screw so the throttle body plate sits completely closed, start the engine and use the screw on the back of the IACV to adjust idle to ~850rpm. Turn car off, plug in IACV restart car. Done.


Can't help you on the TPS though. Never had to do that.

**Edit: FYI, the FSM refers to the IACV as the IAA (Idle Air Adjusting Unit)

[cbh148]

I tried doing exactly what you said to do, and that seemed to help some. It's no longer dancing around as much, but it's still idling too low (~500rpm) and will die if i don't keep revving it. I had it set right at 850rpm when i dialed in the idle with the AAC (IACV) unplugged.

Perhaps I should try again but raise the idle I "set" it at a little higher? Also, I've got a little boost/vaccum leak at my Nismo FPR, as seen here. I wonder if it could be causing it to mess up the idle? Or maybe if my TPS is actually bad? I'll try to get a video of how it reads on the multimeter.
[youtube]http://www.youtube.com/watch?v=ewpgxr7S2ns&feature=plcp[/youtube]

[float_6969]

I think you have a bad TPS. Get a brand new one.

[Buddyworm]

I think float is right. If the TPS isn't triggering the idle switch then the ECU doesn't know to use the AAC to control the idle.

CA's also use a seperate timing map for idle rpms and that can drastically affect the quality of the idle too.

[nickhebert]

with a Ka throttle body do you use the Ca TPS or the Ka TPS

[cbh148]

And where would I get a brand new TPS that would be guaranteed to work perfectly? Should I go through RockAuto as if I own a KA24E 240sx? Or a 1988 Pulsar NX SE?

[Liquid_Neon]

Also.. i dunno if its the same for the rwd manifold.. but i can easily reverse my ficv and my iacv plugs... they share the exact same 2 plug style and the little tabs dont seem to stop them from reversing. Also mind you this is all from my factory ca18de idle stuff, i never modified these. So if mine are reversable and cause all sorts of hell for idle control, I would say make sure you have them plugged in right.

[cbh148]

Yeah I think it's the same kinda setup on the RWD harness, but I do know that I'm using the correct plug just going by what the wiring diagram in the FSM says.

[float_6969]

Any auto parts store is fine, just make sure you get a quality brand with a warranty. I usually got to Advance Auto. I believe they carry a Beck Arnley that carries a 3 year warranty.

After you install it you HAVE to adjust it so the throttle closed switch is actually closed at idle. If it not closed, the ECU won't see that the throttle is closed, and won't control the idle. The variable resistor part of the TPS is used ONLY for accelerator enrichment (like an accelerator pump on a carb) and as such, it's not as vital that it be at any specific resistance/voltage value. The ecu doesn't look at the throttle position itself. It looks at the rate of change of the throttle position to decide how much extra fuel it needs to inject.

[cbh148]

Thanks for the info Float. So i should get a new TPS for a singlecam 240sx right? Didnt i see somewhere that its the same part # as the ca18det unit?

Mine still wants to die when i try to let it idle (and thats after setting it like i was instructed earlier in this thread), and i tried unplugging the AAC valve after a week of it getting on my nerves, and it still wants to die, so im thinking its just set too low. Which is strange cause i had it dialed in to 850rpms when i had the AAC unplugged while i was trying to set it a week ago.

[float_6969]

I think that one will work. Any Nissan TPS that has 2 plugs (one on the body, and the cord coming out with the plug on the end) should work just fine.

[cbh148]

Well that's good to know. I think i'm getting a code 43 from time to time, and i'm not unplugging it at all, so perhaps my current TPS is confirmed faulty.

[float_6969]

Either a bad sensor or bad wiring, but regardless it sounds intermittent. If it were my car, I'd start with a new TPS and see what it does.

[cbh148]

I'm thinking my TPS wiring is fine cause i never got the code 43 when i was running the KA-DE TPS. Also, the car never ever backfired with that KA TPS, but now that i've put the CA18 TPS on (which might be messed up) it backfires a crap ton. And with no exhaust, it's like gunshots going off. Also, when wide open, there's now some spitting/missing. I need that new TPS and maybe a new set of plugs since the set i'm on now has been through 2 break-in periods and a drift event.