Need help bypassing the high idle when the coolant temp is low.

Millie

New Member
Crazy sounding, I KNOW. But here's the thing. When I got the car it had been wire and ecu raped already. (ECU wired for an electronic boost controller and chipped for tuning the current engine) Someone had a different engine with some other stuff going on before the last owner got of it. The previous owner has dropped in a turbo B18B1 with a manual boost controller... The wiring to the coolant temp sensor under the distributor is all jacked up, and some going elsewhere were just hanging around, un loomed and nasty looking. I noticed the temp sensor only had one green/yellow wire going to it, so i decided to get a diagram off the interwebs and try to fix it and the sending unit for the O.E. gauge..Hoping to cure the random idle fluctuations too.. Welp, in the process, I managed to fudge something up and caused the engine light to come on, as well as a very high idle at 21k I may have pulled wires loose in the middle of taping and looming lol. Finally found the jumper to get the code, 6 Coolant Temp, so i know my issue is that wiring mess there. I have the diagrams and pics to correct it, but was wondering if there was some way to bypass the high idle that's associated with the coolant temp sensor and the IAC that has the coolant lines running through it to eliminate my light and high idle.. Any help is highly appreciated :)
 

Russell D

New Member
I believe that sensor is similar to the oil pressure sensor in that it's a on/off switch type once it sees a pre-determined temperature. If this is the case it would work one of two ways, if you unplug it it will open the circuit telling the ecu the coolant is always at temperature, or opposite, grounding the wire will close the circuit telling the ecu it's at temp.

I have no idea how the coolant temp sensor is, I know the oil pressure if unplugged will turn the oil light off, the only way to tell is to try it, or remove the sensor and with a multimeter test if the switch is open or closed when cold, then put the sensor in some water that is ~180deg and test again.

If the sensor is open cold and closed hot then grounding the wire will tell the ecu it's at temp. If closed cold and open hot disconnect and the ecu will think it's at temp

Kind of confusing, but I don't know how else to describe it...
 
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Muckman

Not a M0derator
The single wire sensor is the fan switch. The coolant temp is the 2 wire. I dont think either is related to your high idle.

High idle is usually caused by vacuum leak either by loose/cracked vac hoses, leaking throttle plate, or leaking gaskets on the intake side. Inspect the throttle body. Adjust the idle set screw. Inspect all hoses.
 

Millie

New Member
I checked all of the hoses and have done a vacuum check. It happened immediately after I messed with the wiring.
 


xxBLOOD88SHOTxx

Surge Master
I'm lost as to what the issue was prior to you messing with the wires.

Was it idling high before this? Doesn't the ECT control the fan only and the one wire unit is for the coolant temp gauge?
 

Millie

New Member
Was running fine prior. Had a very minor idle surge at times, but only idled high when cold. Runs great still, just the high idle issue.
 

Millie

New Member
Well, I said to hell with bypassing, guys. Found some wiring diagrams and found my missing wires in this nightmare! All good now :) Thanks for the suggestions guys!
 


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