Engine speed question

Tiny
PATRICK FLOHE
  • MEMBER
  • 2003 BUICK REGAL
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
I have noticed when going down a long and steep hill, throttle closed, that the engine speed hunts up and down from about 1,000 or 1,100 RPM's, to about 1,400 RPM's.
Vehicle speed is remaining basically constant.
I have never noticed this before, with any other car.

Iam not sure if this is even a problem.
Does anyone have thoughts on this?
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Wednesday, September 19th, 2018 AT 3:31 AM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

Do you feel the transmission shifting up and down? At that speed, it looks like the torque converter clutch may be engaging and disengaging.

Are there any codes in the system?

Roy

https://www.2carpros.com/articles/automatic-transmission-problems
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Wednesday, September 19th, 2018 AT 4:21 AM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
No, I do not notice any transmission activity at all.
No codes.
I thought at first, it was only with the cruise engaged, but now notice that it happens with cruise on or off.
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Wednesday, September 19th, 2018 AT 11:38 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, then I would have two things checked.

1. Fuel pressure. need to verify the pressure is not varying and is staying stable.

2. Have the back pressure checked on the catalytic converter. If the converter is partially clogged, it will do this exact issue.

Roy

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Wednesday, September 19th, 2018 AT 11:43 AM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
That does not sound good!

I did check the fuel pressure recently, and it was steady at 45 or 47, I cannot remember which.
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Wednesday, September 19th, 2018 AT 12:15 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Depending upon which engine you have, there are two specs. The eighth digit of your VIN will tell what the pressure should be.

Roy

3.8L (VIN K). 364-405 kPa (53-59 psi)
3.8L (VIN 1). 334-375 kPa (48-54 psi)
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Wednesday, September 19th, 2018 AT 12:30 PM

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