Well everything is hooked up correctly and when I start up the 392 the TBI whistles REALLY loud and doesnt vary in tone unless i hit the throttle. The idle won't drop below 2500rpm either (even when hot).

I bought my harness from AFI, and I was told the wires on the IAC motor from the harness MIGHT be mixed up...however I want to know if you guys have any second opinion on this situation.

One last thing, the idle screw is already turned back all the way, so it isn't that.

:confused: :confused:

Call Norm and talk to him. Maybe a bad chip?

I did this conversion on a YJ and the IAC was stuck. A tap with a small hammer freed it up and the idle dropped and all was good. The whistle sounds like a vacuum leak and it too might cause a high idle situation. This is what I thought my problem was initially, but without the whistle.

IIRC the idle screw has no effect on the idle speed, that is controlled by the ecm.

Update: the high pitched ear blistering whistle is gone, but the TB is running ultra rich. Norm said the wires might be crossed on the IAC...is there a certain way the IAC should look if I take it off and examine it?

Do you have a O2 sensor installed? That might cause it to run rich.

Yes I have one installed(brand new Bosch). I thought you need an O2 to run properly? I will trouble shoot the IAC tommorow and post up some pics...

Have you checked for error codes?

If you look on top of the TBI above the IAC (Idle Air Control) you will see where the air comes from, put your finger over the whole and see if the idle goes down? This would be cutting off the air needed for idle... and also tell you something is wrong with the IAC.

Here's the pin out of the IAC motor, notice how the 454 has two wires reversed? I think you ordered just a harness so you may have got the small block harness wiring. Check the C5 and C6. For that matter check them all. For the same colored wires use an ohm meter.

454
C-3 GREEN IAC W/MALE W/P PIN D D
C-4 BLUE IAC W/MALE W/P PIN C C
C-5 GREEN IAC W/MALE W/P PIN A B
C-6 BLUE IAC W/MALE W/P PIN B A

If your idle screw (min air setting) is all the way out you'll need to open up the throttle plates a little. This still has no effect on idle.

Here's a paragraph from the instructions on how to set your min air adjustment after you get it running.

Your engine may also require more air going through the throttle plates at idle than it is currently set for. Here is a procedure to check this setting. Make sure your engine temperature is at full operating temperature. Jumper Pins A & B of the ALDL connector (I use a paper clip) with the key on but the engine off. This is the same thing you do when checking for engine codes and your check engine light will flash off and on. Wait about 45 seconds or until any trouble codes present have flashed through; code 12 is normal (see #14) After this then unplug your IAC valve which is on the throttle body. Remove the jumper from the ALDL, turn the key off and then start the engine. It may start hard and you might have to depress the throttle pedal a little bit to start the engine. If you have a fast idle this did not work and you may have to tape over the fresh air hole that the IAC receives it air from. If you do not have a fast idle then it is OK and you can proceed to adjust the throttle plates. Let the engine idle for a little bit and then check you idle speed. The speed should be about 550 – 600 in idle or about 100 rpm less than you requested for your chip. If it is lower than this you can raise the idle up or if it is above this determine if you should bring the speed down. More than likely it will always be lower. There is a little cap on the side of the throttle body by your throttle lever that has an adjustment screw under it. Remove this cap and use the screw under there to adjust your base idle speed without the IAC operational. If you have done all of this and you still have an issue we may not have received all of the proper information to build your chip.

Well a little update here...

when observing the TB, it seems to be getting WAAAAY too much fuel! I mean the injectors are spraying like mad, and they just coat the "tunnels" of the TB. When I hit the throttle on it, black smoke comes out from my tail pipes.

I tried tapping on the IAC, no luck there. Also tried covering the hole on it, still idle is too high, and it doesnt drop much at all (maybe 100rpm). THe only way I can get the idle to lower a bit is by turning my sterring wheel to put load on the engine, as it goes under 2000rpm it bogs and sputters, if i continue to turn over and over it will bog it down adn cut the engine. If I let up on the turning it just returns to 2500rpm.

My IAC harness has this:

pin -a -green color
pin -b blue color
pin -c blue color
ping -d green color

Well a little update here...

when observing the TB, it seems to be getting WAAAAY too much fuel! I mean the injectors are spraying like mad, and they just coat the "tunnels" of the TB. When I hit the throttle on it, black smoke comes out from my tail pipes.

Have you checked for error codes?

What TBI unit do you have? From What?

Did you get a chip to match the harness?

With what you described I would check fuel presure first and your return line for kinks or something not allowing the fuel to return will raise presure and casue this! Run the return line into a gas can and start it to see what happens...

Havnt checked for error codes, but check engine is not on either...

I have a TBI from a 1989 chevy van that had a 350 in it.

I got a chip for my 392 custom burned from AFI...

I will try the jerry can trick! Thanks again.

The chip isn't why it's running rich and black smoke problem...

Ummm well I took the return line off the plastic white line i had it attached to (vac canister line). Then I ran the 4 foot hose into a jerry can. At 2500rpm I observed that the TB inner walls were getting COATED with gasoline and the return line only had small drips of gasoline coming out---not even a constant stream.

Is this a TB physical defect? Or do I need to buy a 454 TBI to cure this?

If it were the correct TBI I would still look at fuel pressure on the inlet side while running. Also look at your MAP sensor to see if it's good, no vacuum leaks and hooked up to the line on back of the TBI in-between the fuel lines.

That "whistles really loud" part may also be a vacuum leak too.

Are you running long headers? If you are are you using a heated o2 sensor? The o2 sens may not be getting warm enough to give an accurate reading.

Talked to Norm. He said the chip should be fine. however my fuel line PSI after the pump is at about 25psi. WAAAY to high for TBI he says. I will be installing a fuel pressure regulator to bring it down to about 13psi tomorow...I will post an update and pics if all goes well.

(no headers, just stock exh manif.)


Another odd thing, when I turn my ignition key to the ON position, I see the jets on the TB FLOODING the tunnels with about a half cup of gasoline. THey dont stop unless I turn the key to start the engine.

My fuel pump was defective, it would jump up and down on the pressure. I replaced it and I am now able to "drive" the truck, runs great, but the idle is at about 2000 still. How can I manually lower this? Idle screw does nothing.

Another odd thing, when I turn my ignition key to the ON position, I see the jets on the TB FLOODING the tunnels with about a half cup of gasoline. THey dont stop unless I turn the key to start the engine.Sounds like something is wired wrong? Read instructions and check each conection. The injectors are supposed to spray when the key goes on for a short bit, the reason your's is filling up is probably you have your min air screw closed and the throttle plates have sealed the bore.

Fuel pump does not regulate presure. The regulator in the TBI unit does.

Idle screw is a min air setting and has nothing to do with idle. Your high idle sounds like a vacuum leak.

have you checked your TPS voltage

No I havnt...but it is a new TPS. I will check the value of it for reference though tomrow.

Norman and I worked together today on the phone. He provides excellent customer service (helped me after standard 9-5pm hours) and is really friendly! He told me what to look for--IAC head going in and out, which it is not, its frozen...which means bad computer.

Second, running way too rich (black smoke out the tail pipes at idle). So he is burning me a new chip (leaned out a little more) for the new computer. I highly recommend working with him on purchasing a fuel injection system!

Well I installed the new CPU w/new chip today...STILL same symptoms...what is this electrical gremlin? or could it be mechanical problem? maybe a problem with the throttle body itself?! help.


also i noticed the throttle body gets ICE cold literally, it frosted over in 60 degree weather...what does this mean?

454 throttle body I assume???? They can do that. Some factory applications had a preheater plumbed in under the throttle body. Soon as I get my TBI units back from AFI I can post a pic but doubt this is the reason why you are experiencing idle problems.
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