Idle, TPS, and IAC problems

[93camaro_zzz]

Hey guys,

I am currently tuning the idle on my 2000 Transam with 370ci and 236/232 on a 114LSA cam car, and I am getting some odd things happening. The car has a 90mm Edelbrock Throttle body on it and all sensors are brand new <500 miles on them.

So first things first, at idle, I notice that even with the adjustment screw on the throttle body all the way backed out, the TPS still reads 2% and 0.84V on the hptuners.

From what I have been reading, anything past a certain amount (I have read 0.76V) and the car will not read off of idle tables, etc.

So I figure I will try the TPS relearn thing..... to no avail. I unplug both the TPS and IAC, and turn the key power on from a minimum of 30 seconds, turn off, plug back in, and when I turn it back on, everything is still where it was at before: 2% and 0.84V.

Next problem is the IAC, when the car gets to operating temperature, the IAC counts are around 110-115. So I want to bring those down, so I was going to try the method where I turn up the idle adjustment screw and watch my IAC counts go down to around the 60 range, and then try to reset my TPS from there..... AGAIN to no avail. I start turning up the idle screw and the car gets up to 1800-2000rm with the IAC counts NEVER going down past 105.

How does that make sense? IAC still at 105 even at 2000rpm?

I mostly need to figure out this IAC thing, because my intentions are to turn up the adjustment screw, watch the IAC go down to 60, then slot the TPS holes so I can turn the TPS down to around 0.30-0.40 volts, and then TPS relearn back to 0%.

After all of that, I hope I still go to 100% throttle at WOT, but if not all of this is reversable, and then I would MAYBE consider drilling the throttle blade. But that is absolute last resort in my opinion. There is no turning back from drilling your throttle blade.

Anyone have any ideas on the TPS not relearning, and the IAC acting funny? BTW, this is obviously a cable throttle body.

Here is a log of the car just for grins.

EDIT: and my tune is also included even though I am still kinda working on it.

[mecanicman]

TPS must be set first before you start anything. You may have to adjust later if your tb requires much adjustment. Make it read .5-.6 volt, then do relearn. Relearn does not make it read 0. If it is an actual 370 ci engine your volume is off slightly and your injector data is very wrong. Fix the size, track down the injector data, and adjust tps before continueing.

[93camaro_zzz]

Thanks for the reply.

1. How do I "make" my TPS read 0.50-0.60? By slotting the holes and turning it?
2. I know the relearn doesn't make the TPS voltage read zero, but it should change the TPS persont to 0, am I right?
3. What is wrong with my injector data? I have 60# motron injectors, and I pulled the data from the manufacturer to construct my IFR

Also, what is a good way to find out cylinder volume? Am I right in assuming that cylinder volume would be the following:

(combustion chamber size+dish or dome of your piston in cc's, and then just taking the volume of a cylinder using your bore stroke, and keep in consideration your compressed gasket thickness?

Then converting from cubic centimeters to liters and dividing by 8?

[mecanicman]

1.Yes
2.No, just tells pcm tps starting point and iac to relearn 0 position.
3.There is much more to injector data then just ifr. If you go back to the area where you changed the ifr data all the tables around it must be changed also. If you have the injectors I believe you are describing you can buy the 1st bannish dvd and get the correct info.

piston bore area x stroke x #of cylinders= cubic inch displacement. convert to liters and divide by 8

[93camaro_zzz]

Thanks times 2 for reply. lol

I will look in to the injector data like you said. I own both a Banish's books, but I am reluctant to spend the money on the DVD. Just personal opinion is all.

Using your formula for cylinder volume, it looks like I am 0.0009 off, so I guess I was pretty close after all.

Mechanicman, you have any idea why the IAC counts would not go down past 105?

[mecanicman]

Yes, your engine size was correct. Punched into hpt converter and it takes off to many 0's, had a larger number. The bannish dvd is the only legit way to get the injector data I know of. Your iac comes down to 101, and the tps shows 2%, maybe something to do with it? 0 out the maf table, I see you have 2 bar os but the maf showed .31 through the whole scan. Fix the tps and the injector data and try again.

[93camaro_zzz]

Sounds good. Thanks again Mecanicman!