91 celsior Idle Dropping

[Moarpower]

Hey guys.
I have lovely 91 celsior that needs a little TLC. It look amazing and has had the interior completely reupholstered. 
I just replace the fuel pump, cleaned the throttle body and the IACV hoping to solve this issue.

When cold she takes about 10 seconds to start and will run and idle great until it reaches its operating temp. Then the idle will bounce from around 600 at idle down to almost stalling, and then bounce back up. As the idle is dropping the Engine light at trac off lights flash on, They turn off when the idle bounces back up. 
I have seen the idles hunt up but this is different to what I could find elsewhere. when this starts, if i quickly rev the engine it will stall when i take my foot off suddenly.

[LSPaul]

So, you're getting a check engine light that goes on and off, right? The TRAC OFF light comes standard with a CEL. ;-) 

First up, you'll want to figure out what the check engine codes are.  I'm not certain whether the diagnostic port connector layout is the same as the same vintage as the LS, but you'll want to jumper the correct pins on the diagnostic port (either under hood or under the dash).  I looked at lexls.com for the pin connectors on the occasions I've needed to. Or search the archives here.  You'll need to count blinks with the correct pins jumpered to get the CEL code.

The behaviors you're telling us about makes me think that your issue may be that a bad coolant temperature sensor. There's two of them on the intake manifold, adjacent to the top side ignition coil, under the RH (driver's side on your car) side spark plug wiring loom holder.  They're relatively inexpensive to replace, just use care when removing the connector.

Also not unheard of on early LSes is bad electrolytic capacitors inside the engine ECU, if changing coolant temp sensors ain't the answer.

Good luck!

[Moarpower]

Yes the light flashes in time with the idle dropping down.

I have since changed all spark plugs and in doing so removed the throttle body again. Noticed that the air hose on the throttle body to the valve cover on the drivers side has a huge split. Certainly that is contributing. I will replace the AFM as it is throwing a code 31 , replace the hose and go from there. It is a stunning car and needs to be on the road. The interior and wheels alone is what I paid for the car.

[LSPaul]

Sounds like you're on the right track.  Let us know how it turns out.

I'd love to see pics of the car sometime--it sounds like a stunner!

[Moarpower]

Here are some quick pics. Sorry for the bad lighting and poor camera used.. Cheap phone. I will be starting a thread dedicated to the project and will use my dslr 

[Moarpower]

[LSPaul]

Other than the 'dub' badges, this is quite cool, and in nice shape!  One very minor upgrade you can make to your hood strut prop setup, other than a new pair of struts:  I use a pair of locking pliers/'vise-grips' to lock a hood strut in place (on the rod, against the strut body).  More secure, less likely to bonk your head when you inevitably accidentally knock the stick out of the way.

[Moarpower]

Those badges have to go. I need to purchase a heat gun to remove them tho. 

I will certainly start using vice grips until I get new struts lol.