Which sensor?

Hmm... well I changed the Coolant Temperature Sensor in my 85 IROC (305 TPI H.O.) today but the dash gauge still does not work..? I guess that is not the right sensor, heh. Does anyone know what sensor it is for the gauge on the dash? Where is the sensor located? Thanks a ton.

The sensor you want to change is in the block between cylinders 1 & 3 (driver's side).

The one you changed is the coolant temp sensor...sensors feed the ECM..what you want to change is the sender...senders feed the gauges.

Thanks. Does anyone happen to know the GM part number for the 85 sensor? I can't seem to find it anywhere.

Before you buy a sensor,check your cluster, ground the wire to the sensor and the gauge should max out.

try here, http://www.gmpartsdirect.com/partsvoice/frameset.cfm

Only problem with that is I cannot seem to find the sensor anywhere. The only wires going to the engine block on either side are for the spark plugs. It does look like there is a screw in plug in a hole in between the #1 and #3 plugs though, but still there is no wire leading to anywhere around that area.

Only problem with that is I cannot seem to find the sensor anywhere. The only wires going to the engine block on either side are for the spark plugs. It does look like there is a screw in plug in a hole in between the #1 and #3 plugs though, but still there is no wire leading to anywhere around that area.

There is another switch between the #6 & #8 cylinders on the passanger side. Take the wire off. Does it have a single small threaded terminal, or a spade terminal that the wire connects too?

You could check the gauge in the dash, but it's a bit of a pain to get at, and alot less likely to be the cause of your problem.

The one on the passenger side is the knock sensor I thought? Either way there is no wire going to it whatever it is. The guy I bought the car from swapped motors on it but I am guessing did not hook everything up correctly..? He has some sort of plug with a green and brown wire just hanging above the engine with a resistor jammed in it. Have no clue what that is for either.

He has some sort of plug with a green and brown wire just hanging above the engine with a resistor jammed in it. Have no clue what that is for either.
The plug you are refering to is probably for the IAT (intake air temperature) sensor. It sounds like he put a resistor in-line to bypass the IAT sensor, making the ecm think the incoming air is very cold, thus enriching the air/fuel mixture. This is supposed to "boost" your power, but in my opinion it is just wasting fuel.

Originally your engine would have had a switch on the passenger side where I described. It is behind and a bit above the knock sensor. This switch was used to turn on the cooling fan(s). The sender on the driver's side is for the gauge in the dash. I would venture a guess here that your gauge hasn't worked since you bought the car?

That's correct, it hasn't but the cooling fan is always on. I think also he may have removed the thermostat but i'm not sure. I thought the IAT sensor was on the throttle body? There is no way that plug could even reach the throttle body. Not to say that it is not the IAT though. Could maybe explain why it keeps choking off when it is cold outside..... The odd thing about the gauge is that it sort of moves a little then just sits on the bottom. If there is no sensor hooked up I would assume that there is no way for it to move though. Only thing is that you guys and my chiltons both say that the engine temp sensor is supposed to be by #1 and #3 but like I said there is no wires at all on either side that even go close to the heads. I am very confused...

The IAT sensor is threaded into the underside of the plenum, probably a foot behind the throttle body. If the fans run all the time (i.e. whenever the car is running), he most likely bypassed the switch and has them running off the ignition(hopefully with a relay).

If you want the gauge to work, you will need to replace the plug with the temp sending unit, and find the wire that goes to the gauge. It will be coming through the firewall on the drivers side, behind, and to the right of the master cylinder. There are two main clusters. It is located in the cluster closest to the fender. On my '91 it is a thin, fairly dark green wire. I'll try to varify that you are looking for the same color wire tomorrow.

in the wiring warness of the engine's left side you should find a green wire, that is the wire for the sending unit lacoted squarly between 1 and 3 as mentioned.

Thanks, I'll have to look for that and post back if I can find it or not.

it usually shares a breakout with the o2 sensor wire from the main harness