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My 87' 6.9 idles very high for the first few miles and then finally calms down. It last longer in the winter, maybe 6 miles or so. Is this normal or should I be concerned? Is there anything I can do to address this issue? This is not my everyday vehicle. It only has 110k miles on it and it has taken me three years to put 10k on it.
During this high idle time, does the engine also "rattle" more?
There's a cold high idle/timing advance mechanism on these trucks that steps up the idle and advances the injection timing until the coolant reaches 112 degrees... If you look at the passenger side of the injection pump, you'll see the throttle lever with the throttle cable attached, and you'll also see the high idle solenoid with a plunger that pushes on the throttle lever.
My high Idle doesn't work and I don't know about the timing advance. How would I check the timing advance? If I find it doesn't work where would I look next for the problem? Maybe the coolant sensor? Where would it be located?
Thank You
The high idle won't work unless you press the pedal down first. It will hold the idle at a higher speed, but it doesn't have the power to move the linkage on it's own.
The temp switch for the high idle/cold advance is at the front of the passenger head by the alternator. Follow the wiring from the high idle solenoid...
With the engine cold, turn key on and check for voltage at the high idle and timing advance solenoids.
If nothing, check the wires at the temp switch by the alternator like Phy said.
On a cold engine, all 3 solenoids on the IP should have voltage. Once the engine warms up, the temp switch shuts off and kills the power to the high idle and cold timing advance. (the 3rd solenoid being fuel shutoff should have power whenever the key is on)
All fixed. I found the temp sensor and guess what? It was unplugged!!! It started right up and the high idle worked great. Thanks.. you guys are great!!!