Erratic temperature gauge?

MOBTOWNPSYCO

MEMBER
2001 MERCURY GRAND MARQUIS
V8
2WD
AUTOMATIC
112,235 MILES

This all started after I put in the progressive insurance snapshot thing that goes on the OBD2 scan plug. Within 2-4 days my car started this temperature spike all the way to max then within 3-5 seconds it was back to normal. But while it spiked the car seemed to lose power not cut off but power to accelerate almost like a misfire type. I’ve taken it to 2 shops. The first tried to tell me I had all these problems and needed a new radiator, a new fan shroud relay, but I didn’t believe them. The next shop said the radiator was fine. It was electrical so they replaced the thermostat and coolant temperature sensor but still didn’t fix it. After 2 weeks they officially gave up and didn’t charge me for the cost of the 2 parts. I’ve researched it could be the cylinder head temperature sensor. Which I plan to change. But I’m hoping someone on here has seen this before. Oh, the car isn’t actually overheating the temperature isn’t fluctuating it’s just the gauge for that 3-5 seconds. Thank you

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,724 POSTS

Hi,

If this started when you connected the insurance snapshot component, have you tried removing it to see if things go back to normal? Have you contacted the insurance company and requested a new one due to a defect?

Since the problem started with this component, that is my first suspect. Something internally may be faulty.

Let me know.

Joe

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Thursday, September 21st, 2023 AT 8:19 PM

MOBTOWNPSYCO

MEMBER
3 POSTS

Hello. Yes, I removed it the day it started happening and contacted the insurance company. They claimed that the snapshot wasn’t to blame of course. And I never installed the second one in my second vehicle. Which I figured they would say that but considering they had a class action lawsuit a few years ago from people I believe that was the cause of it. The grand marquis is well kept and probably only gets about 5000 miles a year on it with consistent routine maintenance. Then all of a sudden it starts doing this and I’ve never had an issue with anything on this vehicle. Maybe it’s a coincidence but I don’t really believe in coincidences. The most recent shop had it for 2 weeks trying running diagnostics and trying to figure it out. They replaced the thermostat and the coolant system temperature sensor which are the easiest to get to. They also thought it could have shorted out the PCM or ECU possibly. But they decided not to keep trying to figure it out. I honestly don’t know how I’m depth they went. The first shop said something about a fan shroud relay being faulty and claimed that novo had the part so they weren’t able to do it but then told me it would cost $2000 for a radiator which is completely ridiculous for a radiator that cost $150. I also found a new fan shroud with the relay they said was bad for less than $200 so I’m not sure how honest they were on their end. With the research I’ve done a guy on another thread had exactly the same symptoms and replaced the cylinder head temperature sensor and it was fixed. Others said they replaced a fuse under the hood that had the fuel pump on it and it fixed it. So, I’m kind of not sure what to do except start replacing simple stuff I can probably do. I'm attaching the printout the shop gave me.

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Thursday, September 21st, 2023 AT 10:30 PM

JACOBANDNICKOLAS

MECHANIC
109,724 POSTS

Hi,

The cylinder head temperature sensor is easy to replace but hard to get to. It requires the removal of the intake manifold. See pics below.

If you want to replace it, let me know. There are a lot of directions for removing the intake manifold.

Let me know.

Joe

See pics below.

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Friday, September 22nd, 2023 AT 1:00 PM

MOBTOWNPSYCO

MEMBER
3 POSTS

Okay, thanks. And yes, I do want to change it out I have to order the part my local store doesn’t have in stock. Do you think this will resolve my issue? Or do you have some other suggestions on where to look for what may be the cause? Just by typing into google search “ 2001 grand marquis temperature gauge maxes out for a few seconds then returns to normal “ there’s a lot of people that have had this issue and there are several different fixes that people used on theirs.

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Friday, September 22nd, 2023 AT 4:24 PM

JACOBANDNICKOLAS

MECHANIC
109,724 POSTS

Hi,

There are several different possibilities. It could be something as a simple loose connection or damaged wire. However, to inspect the wiring and connector, the intake needs to be removed. They make nothing easy. LOL

I would get the part first. Then, remove the intake and inspect the connector, and wiring, and make sure the connector is tight and free of corrosion. If everything appears to be in good condition, then replace the sensor.

I attached the directions below for the removal of the intake manifold. They are extensive. However, a lot of the directions indicate to remove connectors.

Let me know if this helps.

Joe

See pics below.

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Erratic temperature gauge?

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