i GOT A 91 FIREBIRD TBI.
I was looking around for for any loose connections; I came upon this wire It's (TAN and BLACK) I didn't find anything unplugged. It's on the left side of the TBI. I really dont know what it's for. i know it must be for something because if it wasn't then it wouldn't be there. Does anyone have an idea what it could be for?

 

looks like a piggtail for the ignition coil or the manifold air temp sensor more likely manifold air temp sensor

 

manifold air temp sensor might be correct but my manifold does not have that sensor in it; nor the hole for the sensor. I am getting a error code 23 for the "manifold air cold" mine only has the vacuum sensor. What do i need to replace it?

mine has this air sensor

 

this (links) is the MANIFOLD air temp sensor aka air charge temp sensor im sure its the one you need
http://cgi.ebay.com/ebaymotors/90-91...ht_9119wt_1165
http://www.rockauto.com/catalog/rafr...251739k1984766

 

So do i just drill a hole in the manifold and pop the sensor in?

 

That same plug connected to the MAT sensor under my TPI plenum near the rear in front of the distributor. It was a 12 inch pigtail the connected to the main harness.

 

follow al intake runners visually.i dont know on yours for sure but usually they are either located there or on air cleaner assy.definitely think its mat sensor harness.

 

Definitely looks like the mat sensor plug. Is there a mat sensor in you AIR CLEANER HOUSING? Mine is located behind tbi (on bottom of cleaner housing, between air filter and tbi system). The the sensor you pictured is the one that helps control the thermac thing, in the snorkel.

If you dont have this sensor there(mat), perhaps the air cleaner housing is not original. I purposely went out and unplugged mine, and it set the CODE 23 as well.

If really no other sensor in your cleaner housing, check local junk yards, or drill the proper sized hole in the BOTTOM of the AIR CLEANER housing

I have a 1990 TBI Camaro.

 

Definitely MAT sensor plug.

 

not in the manifold!!!! as stated avobe do it in the air cleaner housing

 

VERY NICE!!!! this forum need more people like this, willing to get off the couch take their camera and take some pictures to help the crowd here...