Hi guys, I have the 327 running really well with the TPI setup. The only issue I have, and its really minor, is a slightly hunting idle. For the most part the idle is great considering the choppy flat tappet hydraulic cam I have (10-12" vac idling), but it hunts just a little. I was told by a guy who has a lot of experience with TPI retrofits to bring my TPS voltage, once I have set the mininum air, to around 0.68. Why would a higher than stock TPS voltage at idle make the engine not hunt as much. I'm assuming that the IAC counts in the PROM decrease as the TPS voltage increases, so the IAC will be less active?

 

Sounds like he said that assuming that you cannot access the idle screw in the TB. All raising the TPS voltage will do is raise the idle through the ecu.

The correct way is to first set the idle at full temp in gear using the idle screw in the TB. You may have to knock out the plastic cap. Set it as low as you can under the above conditions and still have a fairly smooth idle. Then set the TPS to the correct .53-.55, then reset the IAC. After all this remove the fuse for the ecu to clear it.

Now when you restart it the ecu will use the IAC to achieve the commanded idle RPM. If this is still not high enough you will have to change the commanded idle spd Vs. Temp in your bin file. Then clear the ecu again and restart.

That is the correct way of doing it, not raising the TPS voltage to make the ecu think that you are pushing the gas tiny bit to raise the idle. And see everytime you start the car whatever the TPS voltage is at that point, it will consider it's new min. So if you did increase the TPS, restarted the engine, it would make no difference at all, it will just assume that .68 is the new min instead of .53