ECT; Engine Coolant Temperature Sensor
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ECT; Engine Coolant Temperature Sensor
Trouble Code 18 continued.
Symptoms:
Replace it? Circle Yes or No.
Symptoms:
Surging idle, i.e. 400 RPM to 1100 RPM
Starts good cold; almost impossible to start warm
Temps checked with an IR gun pointed at the thermostat housing; resistance across the terminals of the ECTStarts good cold; almost impossible to start warm
at 62 degrees, 43.7 2k ohms
at 143 degrees, 6.1 2k ohms (edit: 2k is a typo -- 200k is correct)
When I unplug the ECT, the surging idle is gone but it is still very hard to start warm.at 143 degrees, 6.1 2k ohms (edit: 2k is a typo -- 200k is correct)
Replace it? Circle Yes or No.
Last edited by DesertZuki; Dec 14, 2015 at 12:25 AM. Reason: typo
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From: Northeast, OK
Here's where the 1986 EVTM would nail it. (Bill?) That's 'cause my '81 EVTM includes an ECT for the EEC system, but the EFI system wasn't out yet. In '81 the ECT for the EEC was the same as for the gauges, meaning it has a range of 10 ohms at the top temp, to 73 ohms when cold. However, I don't know what ECT was used for the EFI system.
Assuming your "2k ohms" is the scale you were on, then it is quite possible that the 6.1 ohms would be more like 15 ohms if you'd used the 200 ohm scale. And, that would mean your ECT is probably working. However, they are cheap so you might want to change it if fixing the fuel leakdown doesn't fix the problem.
Assuming your "2k ohms" is the scale you were on, then it is quite possible that the 6.1 ohms would be more like 15 ohms if you'd used the 200 ohm scale. And, that would mean your ECT is probably working. However, they are cheap so you might want to change it if fixing the fuel leakdown doesn't fix the problem.
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Gary, could leaky injectors cause idle surge?
Yeah, I just spent $120 on three 1986 manuals, but missed the emissions manual, darn it.
For the ECT resistance check, I was using the below chart. It makes me think the ECT is working, but I wonder about the motor not surging at idle when it's unplugged. I used the 200k (not 2k -- typo) scale as per these instructions: "Connect an ohmmeter between the ECT sensor terminals, and set the ohmmeter scale on 200,000 ohms." from: ECT - Engine Coolant Sensor - FreeAutoMechanic It appears they assume the resistance is universal.
Yeah, I just spent $120 on three 1986 manuals, but missed the emissions manual, darn it.
For the ECT resistance check, I was using the below chart. It makes me think the ECT is working, but I wonder about the motor not surging at idle when it's unplugged. I used the 200k (not 2k -- typo) scale as per these instructions: "Connect an ohmmeter between the ECT sensor terminals, and set the ohmmeter scale on 200,000 ohms." from: ECT - Engine Coolant Sensor - FreeAutoMechanic It appears they assume the resistance is universal.
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From: Northeast, OK
I'm not au fait with EFI, being an old-school carb kinda guy, but I would expect that injectors that dribbled fuel would cause problems with the idle. A drip would cause an imbalance in the air/fuel ratio and probably cause the RPM to drop.
And, the computer knows when you unplug the ECT so goes into a fail-safe mode, and that will change the RPM.
And, the computer knows when you unplug the ECT so goes into a fail-safe mode, and that will change the RPM.
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From: Southern Nevada
Thanks, Gary. I appreciate it.
I'll assume (for now) that it is working and I'll replace the injectors and try it again.
I have to admit to being mystified as how this pickup seemed to run so well when I test drove it, and since then, it's been identify one problem and three more present. Pickup lust maybe...
Edit: I just noticed that in my third post, I posted up the chart for the IAC (Intake Air Charge Sensor). Easy enough mistake, I guess. The values are the same.
I'll assume (for now) that it is working and I'll replace the injectors and try it again.
I have to admit to being mystified as how this pickup seemed to run so well when I test drove it, and since then, it's been identify one problem and three more present. Pickup lust maybe...
Edit: I just noticed that in my third post, I posted up the chart for the IAC (Intake Air Charge Sensor). Easy enough mistake, I guess. The values are the same.
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