Help with as many as possible
ASLO I have seached and what matched my problems either evened up in a different coversation or got left hanging

++++Please note that i am looking for the more indepth "unthought of Cause" of these problems. I have tested the obvious and need different mechanics thoughts++++++++

Oh ya i have done all my testing with "proper tools and gauges. All my diagnostics have not been done with dash gauges"

Car = 1991 Trans am 305 TPI Pretty much stock other than a custom CAI

New parts=
Fuel Pump/Filter
Injectors
Coil - MSD
Cap and rotor - Accel
wires - 8mm Bosch
IAT Sensor ( replaced stock with a IAT sensor with open end )
MAP Sensor
TPS
IAC
New Starter
160 stat
02 sensor
second Fan switch
throttle body hose bypass
All New parts have made big ++++ with no codes a better drivability comparted to when i first bought it.
QUESTIONS:

1st: ( not so much a brain buster here) but how do i know if my car went to limp home mode? Watch are side effects of limp home mode? ( idle, injector widths. Things like that )

2nd: What is the cause of this?
This problem i can not just make happen. Here lately its not been to bad but everywhere from an hour to a week of resetting my computer it becomes a pooch! I"m talking going from having awsome throttle responce to a car with a
v6 and poor throttle responce. I reset computer and all back to good again.
My Diagonsic:
Goes to closed loop
All sensors seem to be operational.
Unforsure bout knock sensor count though

Idle issues.
Did the normal setting/cleaning. After warmed up ( either 190 or 160 ) It will normally idle at rough 650-700 which i like. But every now and again it will drop down to 400-450 ( possibly 500 for the first time ). Now after i reset IAC it goes back to the normal idling. Also when it drops down at a dead punch ( meaning sitting at a red light and it turns green ) it has a bad hesitation.
My Diag:
Just different testing and cleaning.
Clueless

Fan Question:
Problem is Primary fan do'nt kick on at 222 but more like 235 or so. It use to kick on right as it hit the 220 mark. So i know it screwed sumfin up.

Kind of my fault here But would like to fix it. Hooked up a fan switch. I use it to run my secondary fan ( passanger side ). While doing this i grounded out a hot i think. In the middle of wiring this up i got pulled away for a couple of hours and when i came back i must have mixed up the wires in my head. Not for sure which one i messed cause i was tinkering with both prim. and sec. Fan relays. I don't remember how i had it wired but i was driving it the next evening and remember looking down and all the sudden my alt wasn't working ( dim lights gauge read like 10 or so ) U could just tell the car was running off the battery so i Whipped into a parking lot to inspect if it was alt or maybe belt. Got stopped and it went back to charging ok. I was like wtf! But screw it and decided to get home before it left me stranded. Got bout a mile up the road and it did again but did not return to charging. Got it home and I had blown the fan fuse. ( my fan switch wasn't on, wanted to drive for a week or so to make sure computer would take over. ) Anyways, I put a new fuse in it and undid wiring for the evening. Found a new way to wire it up and it hasn't done it again. BUT now my main fan won't kick on until 235 or so. I have no idea what i even done after replacing all relays and everything but at first i couldn't even get the main to kick on, by man. Diag. ( through plug in car ) or with the a/c on. Only secondary. Well i finally did something and got my primary to work but not my secondary so said screw it and just left it where my second its operated by switch ( for 160 stat) I just want my primary to kick back on at 222 again.
My Diag:
All wires good.
Seems all sensors read as should ( not sure which one controls the main tho)
Have good power everywhere and good grounds

KNOCK SENSOR:
ummm donno if i screwed this one up or not yet. I was told if i grounded out the sensor for "over heating" that kicked on both fans would been good way to get both fans to kick on. Well dumb*ss me didn't pay attention and grounded out the knock sensor i think ( not for sure ) Come to find out i was told the wrong location of the sensor i was looking for
Location: passanger side Middle of block with one wire comeing out. tired both with the wire cut and just splicted into it ( with out motor running but key on ) and tried both hot and neg. and got nothing so moved on to hooking up through relays.

Alt Question: ( i know so many of these but a little different here )
This one is a little tricky here
Good charge cold, going down the road and now works good most of the time.
Lets say i have my headlights on , fan switch, and heater on low or so. Some nights it will drop down to where alts not even charging and its running straight off battery. On them nights if i drive it for a long time. then eventually it quits and stays at 13 at idle. wtf its like this car gets lazy on me.
other nights i can have a huge load on it and at idle its at 13 maybe a little lower depending on how huge the load is. Also a wierd buzzing/humming noise.
On my alt its kind of faint but with key on motor off and everything off u can hear a faint humming. Thought alt was shot so bought a new one ( actual parts dealer ). Did it too but was louder, so decided to borrow one off my buddys van ( charging amps the same but had to do 180 on his face plate and his plug only had one wire ) but i hooked it up and it was twice as loud as mine. Is this normal. right now i run the cheapy that was on there that i think was bought from autozone. ( did the same as a/c delco OEM one except the noise wasn't as loud. )
Diagnostics :
New belt,
New Tensoner
Check all connections and grounds
Battery good
Also i know alt will drop in these car at idle and load. Read lots of bout it. And alt is good. Just trying to figure out why it decides to give up on me sometimes, and other its fine.

Remember i've done the easy and lots of searching.

Thanx Derrick

 

ohh lord.

ok. i'll see what i can add.
1st thing. "limp home" mode. just to clarify, "limp home" is actualy what happens when the ECM processor fails. you are probably thinking of "soft fail" mode, which is what happens when a sensor or somthing goes out. see "Grumpy's final answer" vit is indicated by a flashing SES light. you can "throw a code" and not be in failsoft mode however. like an EGR failure. the ECM is not going to go into "fail soft" mode if the EGR is missing. but if your TPS is out it will go into fail soft mode.

2nd thing, what is cuse of this?
i can only speculate that you have an intermittant connection to an important sensor, intermittant sensor, or a bad connection at the ECM. it is also possable that a bad ECM proccessor is causing the ECM to shut down and that you actualy are going into "limp home mode". in which case it is ECM replacement time.

idle issues
my MPFI v6 was doing this when i had a fuel pump on the way out. it was also doing this when i had a bad TPS. i see however that you have replaced all of those. all i can think of is to make sure your TPS is callibrated correctly.

FAN issues
ok, here is the one i am good at. on my L98 (1988) it is layed out like this. 2ndary fan switch is located on the passanger side head inbetween the rearmost exhaust ports.
ECM temp sensor (this tells the ECM how hot the engine is) is loceted under your TB on the front of the engine. it has a two prong plug. this has nothing to do with your indicator guage
GUAGE sensor is on the driverside cylinder head.

to make sure yours is the same unplug the guage one and see if your guage still works. if it does unplug the other cylander head one and see if it still works. i have heard they changed where it was at some point, but don't know for sure.

the relay mounted to the radiator side support is suposed to be for the primary ECM controlled fan.
the relay mounted to the passanger side fender area is for the second cooling fan. to see which is plugged in to where ground the green/white wires on each relay to see which fan each one turns on. now you know which relay controlls which fan now ground the cylander head swithc for the second fan, now you know which relay/fan is controlled by that switch. so you can arange them acordingly.

as far as alternator and knock sensor i am not going to confuse you buy hazarding a guess.