What is the part that I circled in this picture? It's not my car but mine has the same thing and I had a friend who thinks it is supposed to be connected to something.

 

i was wondering the same thing i have a 90 iroc and mine has the same connection with nothing connected to it

 

That's an intake air temp sensor, someone installed it there. Originally it's in the underside of the upper manifold plenum. This location will add more fueling because the ECM sees a colder IAT reading.

 

So is there a wire that is supposed to be connected to it somewhere?

 

That looks to be an air intake from a v6 with the mat sensor installed. as Twin_Turbo said, you should have a mat sensor at the rear of the plenum connected to the wireing harness.

 

JamesC

 

yep. My V6 has that sensor, but it's actually hooked up to something

 

So is there a wire that is supposed to be connected to it somewhere?

You can get a special wire harness that extends from the air temp sensor under the plenum to the sensor on your intake. For example;http://tpis.com/parts/view/157

 

Very interesting. Thanks Twin_ and Red.

JamesC

 

So is it one from a V6 or is it just part of some kit? Does it make any noticable difference from having it plugged in vs having it unplugged? Pros/cons?

 

It moves the IAT from the hotter plenum to the cold airbox, adds a little fueling. May add some HP @ WOT. Cheap mod for a little gain.

 

I might want to look into finding that plug then and try to plug it in!

Another question, where is the EST located on our cars? Mines throwing a code and Chilton says it will throw a code if unplugged.

 

Here it is, underside of plenum.

The wire runs near the distributor, 2 pin connector

 

So is that the EST then? The picture in the Chilton manual is very confusing and doesnt give a reference to where the thing is, just has a picture of a jumble of wiring.

 

That's the IAT, intake air temp. I didn't read your post properly, thought you were looking for the iat.

The EST is the spark timing box, it's near the brake booster, there are a couple of relays on the firewall and a larger black box w/ a red weatherpack seal and a multi pin connector on the engine side. There's most likely a relay mounted on the front of it. It's a thin black box.

 

Ok, so what sort of things will happen if the EST is unplugged (sorry if I seem stupid but Chilton doesnt say what it does either)?

 

The engine will run like crap, if it runs at all. the EST is the electronic spark timing controller, it controls your timing advance and retard as instructed by the ECM and info from the knock sensor.

This is the EST:



See the 3 relays on the firewall? The inner most one is mounted on a box w a big weatherpack connector on the left side , it's right next to the 2 big wire looms and under the black braided fuel lines.

 

If mine is unplugged that would definatly explain why it is running like crap. Thanks for the help everybody. Twin_turbo I will go check on that in a little bit and see what it all looks like.

 

I added a pic to help you locate it

 

What pic?

 

attached pic in post #17

 

Twin_ turbo that's a really nice looking engine bay, and engine!

 

thanks, I have a lot of time and effort into it.

 

Oh so the pack that branches off the left side then? I will go look for it then.

 

Here's what mine looks like atm...

Right now the weather pack has 4 wires in it and the pack has room for 5?

 

So I cracked open the black plastic tube that holds the wires and I cant find any wires hiding in it so I am wondering if that top wire is even very important. Is it?

 

I'll have to check how many are in mine. Don't think there was an empty pinout on the esc

 

Only four of the five connections are used on the ESC module. Also known as the knock filter. With it unplugged the ECM should toss a SES light and code 43. Then pull a set amount of timing which will reduce power and mileage.

The EST control is the ignition control module in the distributor.

On the TPI MAF f-body's the MAT is only used for the EGR turn on temperature threshold.

RBob.

 

So... that means...?

 

Oh I see I goofed, I mixed up est and esc, my bad. Yes, the est is inside the ign module.

 

So how do I get to that to fix it? Would it have all the same symptoms?

 

Remove the distributor, pull the cap and rotor and you can unscrew the est. it's the black part where the 2 weatherpack connectors go in the base..

 

An EST error will set code 42. This will also occur when the EST/BYPASS connector is open, such as when setting the distributor base timing. So if the SES is on and code 42 is active, then make sure that the EST/BYPASS connector is firmly connected. Found over on the passenger side near the A/C box. Single tan with black stripe wire.

If the code 42 is only stored (not active) and the timing has been recently set, then no worries about it. After 50 good start ups the ECM will clear the stored code(s) for you.

RBob.