How does a faulty temperature sensor cause my car to accelerate without input and redline when stopped?

2000 VOLVO S40

11,200 MILES

MISSLYSS0829

MEMBER
2 POSTS

My Volvos fan was constantly running and outside temp reading seemed high most days, then I started having acceleration issues. My car would take off without me touching the gas. It would even accelerate when I was on the brake. Then I restarted it and the car instantly red lined. Brought it to mechanic twice and they finally figured out it was due to a faulty temp sensor. How does that work? And why would that make my car accelerate? Very scary. Should I replace ETM as well? Please help

Apr 4, 2012 at 11:17 PM

WRENCHTECH

✓ASE Certified Mechanic
20,761 POSTS

Because it's telling the computer that it's 40 degrees below zero outside and the computer richens the fuel mixture and raises the RPMs accordingly although what you are describing sounds too extreme.

Apr 4, 2012 at 11:59 PM

MISSLYSS0829

MEMBER
2 POSTS

So this has nothing to do with the throttle?

Apr 5, 2012 at 12:05 AM

WRENCHTECH

✓ASE Certified Mechanic
20,761 POSTS

Who said that? I just said that the computer will raise the RPMs because it thinks it's real cold outside.

Apr 5, 2012 at 12:08 AM

JIS001

✓ASE Certified Mechanic
3,412 POSTS

Has nothing to do with the throttle. This model does not have the electronic throttle module so there is no "ETM". Still a cable on this. But yes like Wrenchtech says the faulty reading will cause the computer to open up the idle air conbtrol valve to increase the RPMS to try and warm up the engine since it thinks it is very cold.

Apr 5, 2012 at 3:17 AM

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