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Old 09-30-2018, 12:59 PM   #1
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Default Twitchy temp gauge

Truck is a '97 4cyl. Coolant temp is steady per ECU right around 170, but the gauge acts a damn fool. Sometimes it dips inverse of throttle input; other times it gets super jumpy while either at idle or steady cruise like a nervous twitch. I'd noticed it dip under load a couple times in the past, but today it happened every trip driving around town. I take it it's the coolant temp sender for the gauge, just asking before buying and replacing parts.






Truck has also been hunting idle when cold. This is not consistent. Only happened a few times when it was pretty chilly out and normalized when the motor warmed up. Tonight it did it very slightly.



Ideas?
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Old 09-30-2018, 03:11 PM   #2
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Check the connection at the temp gauge sensor. It is a blade connection which can become loose. Also check the ground on the intake manifold.
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Old 09-30-2018, 04:25 PM   #3
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^^^what he said. Clean the spade terminal on the sensor with a wire brush and try it again before you spend any money. It’s most likely a poor connection due to corrosion.
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Old 10-01-2018, 10:33 AM   #4
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Thanks a lot, guys. Did as y'all suggested and the problem cleared. A previous owner or mechanic used a shit ton of white lithium grease as a dielectric in a number of plugs. Learned this a couple weeks ago when I changed the alternator and the fusible links were caked with it, as was this sensor. Sprayed them clean with electrical parts cleaner.
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Old 10-01-2018, 11:15 AM   #5
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Truck has also been hunting idle when cold. This is not consistent. Only happened a few times when it was pretty chilly out and normalized when the motor warmed up. Tonight it did it very slightly.
If this is still going on, could you check for a code?

It may have gone away when you cleaned the temperature gauge contact.
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Old 10-01-2018, 11:21 AM   #6
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If this is still going on, could you check for a code?

It may have gone away when you cleaned the temperature gauge contact.
That sensor goes directly to the gauge cluster, it can’t cause a code. There is another coolant temperature sensor for the computer.
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Old 10-01-2018, 11:38 AM   #7
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My thinking is that when Hands On cleaned the contact to the temp gauge, he probably would have cleaned the contact going to the ECU.
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Old 10-01-2018, 06:43 PM   #8
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It's not throwing any codes. I read around on the internets but haven't come up with anything worth noting as yet. Sucks trying to diagnose and repair temperamental problems. And this one is only exhibited when the motor is cold too.
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Old 10-01-2018, 09:33 PM   #9
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It's not throwing any codes. I read around on the internets but haven't come up with anything worth noting as yet. Sucks trying to diagnose and repair temperamental problems. And this one is only exhibited when the motor is cold too.
Then it's got to be a vacuum leak or a loose electrical issue.

Since it only happens when it's cold, I'm leaning towards a vacuum hose that doesn't seal very good until the motor has a chance to warm it up.

Of course, not a mechanic. Fook if I know, right? lol
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Old 10-02-2018, 02:08 PM   #10
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I'm no mechanic either, just play one when I look at my account balance.


This seems more like an engine management issue. Vacuum leaks usually cause rough idle, and mine just varies up and down a bit instead of keeping a steady, constant RPM.
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