86 GT 2.8. We all know that the 235* factory temp is scary, and excessive heat can cause damage over time. Well in trying to get my temp down I installed one of RD's lower in-block fan temp switches and a 195* stat ( I forgot what the stock thermostat was). I think the 235* came in with the original in-block fan temp switch. Engine is mostly running in closed loop now. Does any one out there have a good combo of stat, and switch that would run it closer to 200? I think it's supposed to go to open loop at about 160, and I'm consistently running at or below that.

[This message has been edited by FX (edited 07-05-2019).]

quote Originally posted by FX: I think it's supposed to go to open loop at about 160, and I'm consistently running at or below that.

What are you basing that observation on? If true, I suspect your thermostat is stuck open.


You might possibly be getting confused between the temperature ratings of the fan switch and of the thermostat.

The factory thermostat is 195°F. The Stant SuperStat (#45819) is a superior 195°F thermostat.

The factory fan switch turns on at 235°F. Many of us swap that out for a 210° on and 200° off fan switch.

None of the changes mentioned here will affect closed loop operation.

[This message has been edited by Patrick (edited 07-05-2019).]

Patric, I'm basing this on the temp gauge, and poor mpg, it's not running in open loop. My objective is to run in open loop without the fan on almost constantly. I don't want it to fail before it's time. I will install the thermostat you suggest, you could be right on it sticking open. I do have Rodney's lower temp switch installed.

quote Originally posted by FX: I'm basing this on the temp gauge, and poor mpg,...

You can't trust the dash gauges. Using a scanner, you need to see the actual temperatures being reported to the ECU.

Poor MPG could be caused by any number of factors.

quote Originally posted by FX: ...it's not running in open loop.

You don't want it to be running in open loop.

quote Originally posted by FX: My objective is to run in open loop without the fan on almost constantly. I don't want it to fail before it's time.

This makes no sense. You want the engine to be running in closed loop. I have the fan switch and thermostat previously mentioned installed on my Fiero(s). The rad fan rarely comes on.

[This message has been edited by Patrick (edited 07-17-2019).]

Then I got it backwards...Closed loop, operating temp, when it leans out the mix....And I don't have an obd 1 scanner...

[This message has been edited by FX (edited 07-05-2019).]

https://youtu.be/XutHcwaWUpY

Easiest way to tell if you're running in open or closed loop with no scanner.

"If the engine controller is in open-loop mode, the MIL will flash extremely rapidly, about two-and-a-half times per second. If the engine controller is in closed-loop mode, it will flash about once per second."

[This message has been edited by cebix (edited 07-05-2019).]

Thanks cebix, I will check this out.