I know I seen this on here the other day, but I can't seem to find it again. What order should I adjust timing, IAC, and TPS? I know that one effects the other, so which one first?

 

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Thanks. Now I have a related question. I was trying to follow the directions that were posted out here for adjusting the TPS, but it just talks about making jumpers between the TPS and the connector and reading the voltage. There are 3 wires, which wires am I supposed to be reading? No matter which wires I checked, I never got any readings even close to the suggested settings.

 

That answer is incorrect. It should be timing first, idle speed, then TPS. If you set the TPS first, and then do the idle, you are already moving the arm forward or back on the TPS while adjusting idle speed. You set the idle speed first, then adjust the TPS to adhere to that position.

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1989 IROC-Z 5.7L

 

Omar is correct.

You MUST set the IAC (minimum air) first, then adjust the TPS.

But opposed to Omar, I do the timing after I set the IAC and TPS.


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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(48psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
ET 13.39sec @ 107.21mph
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313.7Hp & 320.6ft-lbf, ET 13.55sec @ 105.1mph
next mod: 4.10 rear gears

 

Thanks Omar. I guess you gotta be carefull of who you get your information from.

 

The top two wires are what you're after on the TPS. Crud, which way is it.. I think the middle one goes to positive on the meter, the top one goes to ground?

Can someone check me on this?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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Tom, it is the top 2 wires, and it shouldnt matter which one you connect to positive or negative.

Doc, I think it is neglible on doing the timing first or last. I used to do it last, but then I got to reading my shop manual. It said to disconnect the EST wire when setting the minimum air, because changes in timing, such as the ECM advancing it, could also bring changes in idle speed. So since i am disconnecting that wire anyways, might as well do the timing first. Of course, the thing I didnt understand was this...You figure that if the ECM advances timing on you, then advances idle speed, it would do so by opening up the IAC more, right? Well, step one of the ENTIRE process is to ground the ALDL, wait 30 secs for the IAC to close and disconnect the IAC. So how would the ECM advance idle speed with it closed and disconnected? Go figure. I just do it first and go on with life.

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1989 IROC-Z 5.7L