7 replies to this topic

[Alberto]

While at the dyno a couple of weeks ago at MCE at Thunderhill, my car's performance suddenly started to fall off from one run to another with a minor change in tune.  This was after an hour and a half of tuning on the dyno.  Kevin thought it might be the stock coolant temp sensor getting heat soaked or not performing as expected for whatever reason.  

 

The sensor is original to the engine w/ about 92k miles on it.  Vintage 1991.

 

Questions...

 

Is the stock coolant temp sensor (at the back of the head) susceptible to heat soak?

What is the failure mode for that coolant temp sensor?

Is there a way to test it?

 

Thanks.

[Bench Racer]

 

 

Is there a way to test it?

 

Thanks.

Yes, in the FSM, F-136. $25.00 for a new one at a parts store.

[Alberto]

Thanks.  Couldn't find it in the FSM cuz I was looking in the wrong section...

[SaulSpeedwell]

Thanks.  Couldn't find it in the FSM cuz I was looking in the wrong section...

 

Hit 204F (at the stock sensor at the back of the head, which may not agree with your Autometer or similar) and the ECU retards timing, instant loss of 3 to 4 HP

[davew]

Also check the wires going to the green plug, they have a tendancy to pull out of the connector. No connection and it goes pig rich. Only way to tell is to unplug the connector and look from the end to see if both wires are pushed through properly

 

Dave

[DrDomm]

Hit 204F (at the stock sensor at the back of the head, which may not agree with your Autometer or similar) and the ECU retards timing, instant loss of 3 to 4 HP

 

Same on '99s?  My car routinely gets that hot.

[SaulSpeedwell]

Same on '99s?  My car routinely gets that hot.

Yes, still in the 204-210 range, depending on tolerance.

 

Your Autometer could be BS-ing you if it was installed "improperly", so it is best to go off of OBD-2 data for this.

 

Point being, run a big rad, seal the rad to the body and bellypan with rollcage foam and tape and stuff, and don't block 20% of your bumper cover inlet with mesh.  Move the mesh out of the bumper cover hole (1" behind it) so you aren't turning the bumper cover into a cooling air "restrictor plate", eh?  That is one of the most common prep mistakes I see on SMs in the paddock ...

 

Up here in the North, you should be able to keep the car at the thermostat temp except when in the draft or an exceptionally hot day ....

[DrDomm]

Thanks.

 

(Yes, temp gauge does read about 5 degrees hotter than OBD2.)