RPM's dropping and recovering

Tiny
JRLAG
  • 1999 CHEVROLET MALIBU
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 130,000 MILES

My wife called me this morning concerning her car listed above, I believe it is the 3.1L engine but will confirm that later if it makes a difference. She was driving down the highway when suddenly she said the tachometer dropped to 0 and then recovered a second later. She said it "felt" like the car was shifting very hard, and that it did this multiple times. She pulled over into a parking lot and even when in park, it would continue to drop to 0 and recover. I am asking for some opinions, to me it sounds like fuel pump or fuel pressure problems (maybe even a clogged filter?). I am open to suggestions on what others may think it could be. I just hope it is not the fuel pump because those are a pain to replace. TIA.

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Friday, January 12th, 2018 AT 1:22 PM

6 Replies

Tiny
ASEMASTER6371
  • EXPERT
  • 25,848 POSTS

Good morning.

Yes, it sounds like a failing fuel pump. You need to get a tester and test the actual pressure. There is a tap on the fuel rail by the power steering pump. You can rent a tester at a parts store.

Roy

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Saturday, January 13th, 2018 AT 3:57 AM
Tiny
JRLAG
  • MEMBER

I just uploaded a video showing it while idling in a parking lot. I will see if I can go rent the tester today and get back to you. I will probably hook it up to check for any thrown codes but the check engine light is not on. Just want to be thorough. Thanks!

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Saturday, January 13th, 2018 AT 6:23 AM
Tiny
JRLAG
  • MEMBER

Well I hooked up the pressure gauge and it read 35 consistent. Reving the engine fluctuated very slightly but always returned to 35. Maybe it s not as bad as I thought? Gonna add heat with fuel injector cleaner to see if it s just bad gas

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Sunday, January 14th, 2018 AT 8:49 PM
Tiny
ASEMASTER6371
  • EXPERT
  • 25,848 POSTS

Ok, the spec is 41-47lbs for the pressure. 35 is too low. You need a fuel pump.

Roy

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Monday, January 15th, 2018 AT 2:43 PM
Tiny
JRLAG
  • MEMBER

Could it also be the regulator not working correctly? I appreciate your responses ASEMASTER

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Monday, January 15th, 2018 AT 9:29 PM
Tiny
ASEMASTER6371
  • EXPERT
  • 25,848 POSTS

Glad to help

You can try clamping off the return line to the tank and re test but regulator failures are rare.

Roy

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Tuesday, January 16th, 2018 AT 2:23 AM

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