ECT Sensor Quick Question

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Feb 23, 2008 | 08:28 PM

floridasun1983

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ECT Sensor Quick Question

Since replacing the TPS on my dad's 85 F150 302 carb'd truck, its back running well, but one thing he and I both noticed, it seems to be stuck in "fast idle" that you expect during warm up. The motor doesn't idle down to normal speed once the engine is warmed up. I pulled codes on it from a KOER test and it came up with a code 21, which indicates the ECT is out of spec. My question is, could a faulty ECT sensor be tricking the computer into thinking the engine is perpetually cold, and thus be responsible for the fast idle? Thanks in advance.

Feb 23, 2008 | 10:13 PM

Franklin2

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It could be. But make sure the engine is warmed up before pulling the codes. If it's below 50 degrees, it will spit out a code from the temp sensor.

Also make sure your throttle blade is clean, and is set correctly. If it's open too wide, or the idle air control motor is gummed up, it can stick and cause a high idle.

Feb 23, 2008 | 10:41 PM

floridasun1983

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Quote:

Originally Posted by Franklin2

Thanks. Engine was warm (had just returned from a 15 mile trip and with a bad fan clutch, it gets really warm, will be working on that in a few days). Nothing seems out of the ordinary, it idled fine before the TPS went haywire. The EGR system appears to be totally shot as well, but I'm working on one problem at a time.