TPS, IAC Adjustments

[MysticKeith50]

Is it true that the TPS on our cars can be "adjusted" by loosening the screws and turning it a little? I am having a tiny little idle issue since H/C/I(yeah like I didn't see that coming.) Call JMS about my custom SCT chip, and they told me to set the TPS/IAC and check for vacuum leaks, which was probably the issue. Now I might mention that at 10:00pm at the end of the day we did the swap, I basically just threw the damn TPS and IAC on the throttle body. We never set the things up, and also never reset the idle. Also could someone tell me what those things actually do? I am just trying to get my facts in order before Tuesday when we attempt to make it right. Also I deleted the EGR and had it turned off with the chip. The little vacuum snap on cap thing that used to pop onto it, would that create a vacuum leak? Just curious. It is amazing how quick I can rip this chit apart, to do H/C/I, but how long it takes me to understand this idle situation! I would get a PMS or tweecer, but I am scared to death of those things. Thasnks for any response.

 

[HISSIN50]

Cap the EGR vac line so you dont have a leak.

The TPS is supposed to baseline if it can, and otherwise it should spit a limit code. That said, adjust away. You would probably need to rheam out one of the bosses in the TPS, so you can 'swing' it to the DMM reading you desire.

I prefer to set the warm idle with the idle stop screw, rather than the idle bleed adjuster (the latter is how at least one manual suggests adjusting the idle).

The TPS is a rheostat of sorts. It relates to the puter how much the throttle is open, and is used a lot for transitional changes (on and off throttle - think Auto X-ing). The other sensory input in those split-second transitions can lag or be a little strange, but the TPS value is absolute and instantaneous, which is why it is critical.

The IAC is a controlled vacuum leak. It keeps the car idling when the throttle blade is closed (some guys set the idle so it is not needed at hot idle with no load). But even so, the IAC is needed for cold idle enrichment, load compensation, rolling idle compensation, etc.

Good luck.

 

[HISSIN50]

Here is an article which provides ancillary info and could be useful for getting you in the ballpark.
Each page offers a different aspect of the idle setting procedure (note that the article is primarily MAF Fox based, but the 5N95 guys have luck following it).

Good luck.

 

[MysticKeith50]

Thanks, very useful info....anymore...anybody...

 

[R.J.]

Try adjusting your IAC like this:

Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.

The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using a 0.010" feeler gauge, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.

Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.

Obviously, this rpm range is by what the car and driver wants...IE, no set idle speed, whatever works for YOU.

Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.

If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, and then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC. You are done.

 

[RIO5.0]

Granted I run a Fox set-up but the link Hissin posted I have personally done and it flat out solved my idle issues...
The one RJ posted is more towards the SN set-up....I would do his first as its more SN related....either way a full idle reset needs to be at least tried to see where it gets you...

I did the first link with the car cold....it worked instantly as that where my problem lied, at start-up....
I don't know how much faith to put into the "TPS baseline resetting at idle" and being non adjustable, or not worth trying to reset it...As some have done it and seen results...No two of these cars seem to re-act the same sometimes. I would want to see those readings for myself and then make a decision on whether to tweak it or not....
your gonna have to play with it some..

Where's the timing and fuel set to???

 

[MysticKeith50]

the timing is 10 degrees and i believe the fuel is 39psi.