My 88's high idle never shuts off unless I unplug the wire going to the solenoid. My Cold Timing Advance does work and shuts off when engine warms up. I know that the Cold Timing Advance and the High Idle Solenoid are both of the same temp sensor which is located beside the upper rad hose on the passenger side, so that means the temp sensor is working. The plunger on the solenoid goes down when I pull the wire off? Any ideas? Thanks in advance.

 

i have problems with mine too. if i plug in the factory wire the cold idle solenoid pushes out too far causing my rmps to be way over 1000. But i wired a switch in connected straight to the battery and it only goes to around 900-1000 like it should. timing advance seems to work ok. On yours it may still be the sensor in the block not shutting it off.

 

mine went out a while ago, so i just ran a switch inside the cab to both the high idel and cold advance. be careful though you do not wan to drive around with the advance on. people have ruined their pumps that way.

 

Just replace this sensor behind the alternator and thermostat housing and you should be good to go.

 

I will try to find one at a junk yard. Thanks for the help guys!

 

It is about a $25 part new, I would never get a sensor or any electrical part from a JY, that is just me though...

 

WHERE? i checked every parts store in two counties when mine was having problems and nobody even had a listing on it. i finally went with one from the junkyard

 

Rockauto.com has listed between $6 and $44 depending on what exactly you want. The Motorcraft part is $35.

 

i just checked their site, and found the same selection found at napa or oreilly, which doesn't include the sensor for the cold timing advance and high idle.
only place i haven't checked is at the dealer.

 

Good to know, I assumed that the ones with the plastic connector were for the high idle and the others with the pin were for the gauge.

 

i assumed that too until i actually looked at it. it just has two 1/4" flat blades sticking up about half an inch apart, with no housing around them.
on the day i got mine at the junkyard, i grabbed 2 from fords, and one from a chevy of a similar time period. the chevy had the same electrical end, but screws into the engine on 3/8NPT threads instead of 1/2NPT like ours are. i took it anyway, and its bouncing around my toolbox somewhere.

 

according to the guy at napa, the one with the plastic connector is listed as a fan sensor/thermostat. i didn't know our trucks ever came with electric fans, so i suspect they don't belong in the catalog for our trucks to start with, but thats a side-note