I just picked the truck up 4 a really good deal and am new to fuel injection(not new but only carbs).Heres prob. #1.I constantly have high idle searched and found it might be vacume lines or a bad tbi gasket,I took the drivers side front vacume line off and the box that it runs to is doing nothing,so I take some spare line and bypass the box from tbi to the modulator on the trottle arm and I got the idle down to about 900 rpms(still not right)
#2 Once the truck warms up it does not get the power it should and the idle exhaust has a popping sound(like a miss) but if you get above 3000rpms it's normal.It also has normal power when it's in choke mode.
#3.The truck has a slight charging problem,so today I changed the alt. and it's still not charging right.The prob. is with no lights or draw I get an allright charge.So where should these wires go, I have the big from batt. to starter.Then I have about a 10 ga.from bat. post on the alt. to + on the batt.Then I have another about 8 ga. that seem to feed the truck.Is this right and if not what could be the problem.
#4.What is the IAC.
Thanks all.

IAC is idle air control. it is in the tbi unit and opens to let air flow around the butterflies so the engine can have some control ove idle, and from what i hear, it helps make sure that when u r wide open and then suddenly let off and the butterflies close, it doesnt create too much vaccum, if what i was told is correct.

I'm having the same problems w/ my 94 454 suburban. I put a new engine in it about a month ago and since then can't get it to run right. The idle is now about 1300 and after it warms up goes up to 2000. another problem is there is no oxygen sensor (so the computer never goes into closed loop) and there wasn't before the engine swap either and it ran great before(just had some blow-by).I have scanned it repeatedly and no codes or anything unusual. I thuoght maybe bad grounds ,so I ran all new grounds from batt. to body to engine and frame. Now my charging system is better than ever but didn't fix my other problems.
also the electric cooling fan stays on all the time now when the key is on.
My a/c system is not working either. no matter what I do I can't get any response. I tried jumping the low pressure switch and still nothing.
The frustrating part is that everything worked fine before the swap, even w/ no oxygen sensor.
You asked about an IAC. It is the Idle Air Control motor. It regulates the air flow at idle.
good luck, if you come up w/ anything let me know.

both engines sound like they have intake gasket or TBI gasket leaks.
The tbi comes off with just 3 bolts. and you don't have to remove anything from it. just remove the bolts and lift it up about 3-4", then use a scraper to gently remove the old gasket. the back edge is the ussal place it pull in.
the poping noise maybe the lean condition you have because of the vacuum leak. it detenating and the fuel is causing the pistons to run to hot.
it could also have the timing off. if its to retarded ,the exaust will get so hot it lights unburnt fuel at the manifold.
as for charging the large wire is the from the distribution center. it should have a junction with more wire coming from it.
if the charging system is making 13.5 -15 volts you are ok.

The system cannot operate without an o2 sensor. if its where it belongs its in the pipe on the right side of the trans.

"The system cannot operate without an o2 sensor. if its where it belongs its in the pipe on the right side of the trans."
I know it sounds crazy but I've been driving it for more than a year without an o2 sensor. The computer has a preset air/fuel ratio that it reads until it goes to closed loop. before closed loop it is in a cold start mode and does not use the o2 sensor.

I'm having the same problems w/ my 94 454 suburban. I put a new engine in it about a month ago and since then can't get it to run right. The idle is now about 1300 and after it warms up goes up to 2000. another problem is there is no oxygen sensor (so the computer never goes into closed loop) and there wasn't before the engine swap either and it ran great before(just had some blow-by).I have scanned it repeatedly and no codes or anything unusual. I thuoght maybe bad grounds ,so I ran all new grounds from batt. to body to engine and frame. Now my charging system is better than ever but didn't fix my other problems.
also the electric cooling fan stays on all the time now when the key is on.
My a/c system is not working either. no matter what I do I can't get any response. I tried jumping the low pressure switch and still nothing.
The frustrating part is that everything worked fine before the swap, even w/ no oxygen sensor.
You asked about an IAC. It is the Idle Air Control motor. It regulates the air flow at idle.
good luck, if you come up w/ anything let me know.
i had the same problem with my 454 tbi when doing my swap. i was getting no codes for the iac but i replaced it anyways, but it ended up being that i had it wired wrong b/c i had to change the plug to a different style...

Thanks guy's i'll keep trying and let you know what I come up with.I am going to try the gasket in the morning.Thanks again

Any update on these problems? I have a 93 with similar symptoms...

thanks