Below-spec acceleration - Why?

Tiny
TEHAMMER
  • MEMBER
  • 2003 OLDSMOBILE ALERO
  • 3.4L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 88,000 MILES
My car seems to have a slight performance issue. Everything functions and runs normally, no stalling, rough idle, or failure to start. However, the car accelerates slightly slower than it should. 0-60 takes 10+ seconds (even with brake launching) when it should be 8 seconds or less. There's plenty of tread on my tires and the transmission seems to shift fine. It has a new fuel filter, air filter is clean, catalytic converter is not clogged and the spark plugs are brand new. I know it's not a major issue, but if I'm getting V6 fuel economy, I'd like to have V6 power available too.

The only thing I can think of is a fuel pressure problem. I had the fuel pressure tested for a different problem earlier and they said it was about 4 psi below spec, but my car isn't giving me any of the classic fuel pump failure signs (difficulty starting, losing power while driving, lurching, etc.). Would fuel pressure 4 psi low give me my performance issue? Could it be something else? How do I diagnose this?
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Friday, March 4th, 2016 AT 3:43 PM

11 Replies

Tiny
WRENCHTECH
  • EXPERT
Where are you getting these numbers from? Why do you think it should be faster?
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Friday, March 4th, 2016 AT 4:37 PM
Tiny
TEHAMMER
  • MEMBER
Motor Trend tested a stock Alero at 7.8 seconds back when the car was new. I also had to have the engine replaced recently, and the engine came out of a Pontiac Aztek. The Aztek version of the 3400 is rated at 15hp more than the Alero 3400, so if anything it should be slightly faster.
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Friday, March 4th, 2016 AT 4:44 PM
Tiny
WRENCHTECH
  • EXPERT
You took an engine from an Aztec and you are operating it with a computer from an Alero. There can be major differences there. You can't expect every vehicle to perform like a test vehicle. It just doesn't happen.
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Friday, March 4th, 2016 AT 4:55 PM
Tiny
TEHAMMER
  • MEMBER
So what could I do to improve it? The engine has less than 90,000 miles, so it shouldn't be too worn. I'm not getting any computer errors.
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Friday, March 4th, 2016 AT 5:05 PM
Tiny
WRENCHTECH
  • EXPERT
If you're not getting any computer errors then that means the computer is satisfied with the way the systems are operating and there isn't much you can legally change.
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Friday, March 4th, 2016 AT 5:07 PM
Tiny
TEHAMMER
  • MEMBER
So then the question still stands, why the performance difference? It is a nearly identical engine, and yet 2+ seconds is quite a difference. Would 4 psi low fuel pressure cause less performance without giving any other negative symptoms?
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Friday, March 4th, 2016 AT 5:09 PM
Tiny
HMAC300
  • EXPERT
If the pump doesn't meet spec the performance will be down. 52 psi
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Saturday, March 5th, 2016 AT 7:53 AM
Tiny
TEHAMMER
  • MEMBER
Are there things I should check before replacing the pump? Like fuel lines or wiring or anything like that?
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Saturday, March 5th, 2016 AT 8:16 AM
Tiny
HMAC300
  • EXPERT
Only a fuel filter even if you replace filter it won't make much of a difference anyway.
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Saturday, March 5th, 2016 AT 8:34 AM
Tiny
TEHAMMER
  • MEMBER
Okay, thanks!
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Saturday, March 5th, 2016 AT 8:47 AM
Tiny
WRENCHTECH
  • EXPERT
If you're not getting any lean codes, then the pressure wouldn't be effecting anything. You'll be wasting your money to replace the pump.
The spec for the Alero is 52 to 59PSI and the Aztek is the same.
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Saturday, March 5th, 2016 AT 9:42 AM

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