Please check your vacuum lines! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-25-2004, 07:38 PM   #1
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Default Please check your vacuum lines!

I recently looked under the hood thinking about what to do as in engine detailing and painting. For the up and coming Pontiac day next year at Englishtown,NJ.
I glanced over at the fuel pressure regulator(because it is shinney) and bam.
I had a perforrated vacuum line to the pressure regulator. Didn't hear a peep from the engine in regards to a vacuum leak, car ran and started fine, the idle was a slight bit lumpy but just alittle with 116k plus thought it was normal.
I look around my tool box and found some vacuum hoses, I had to slip the skinny one into the fatter one because the ends of fittings are different sizes.
Buttoned it up and took her for a spin, noticed a big difference right away in response even squealled the left front tire a bit.
So when checking your vacuum just don't look at them, apply pressure to them bend them check for cracks and perforrations.
My tip for the day.
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Old 08-25-2004, 09:16 PM   #2
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Spank you very much. Great advice. I've been bitten by small leaks twice on my car.
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Old 08-25-2004, 11:38 PM   #3
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Good tip

-and I find it interesting to think about what potential effects (if any) that would likely occur with that vacuum line completely off. AND your expressing that everything was still running just fine is exactly what I'd expect. Here is why: with that particular line disconnected, the regulator increases the fuel rail pressure by 10 psi (from about 40psi to 50psi) -which should not cause any changes in engine operation. Also, the small amount of vacuum leak caused by that small line will also not affect normal engine operation. (-even at idle.) BUT I'm sure that GM had good reason to not run the pressure at 50 psi all the time.

So, in my mind, that lends even more importance to your good advice of checking things over thoroughly.

PS. -speaking from personal experience this last weekend with other fuel system problems, which involved checking the regulator for proper operation by reading rail pressure while alternately removing and installing that vacuum line.
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Old 08-25-2004, 11:48 PM   #4
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Wow ... deja vu.

I had my car looked at today, and we noticed one of my vacuum lines cracked away.
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Old 08-26-2004, 07:33 AM   #5
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Great tip...

I found both of mine on the throttle body completely cracked. Had to go to the dealer to get the replacements. Car ran shaky too...all good now.
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Old 08-26-2004, 09:28 AM   #6
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Default lines

Thanks for the tip. I'll be sure to check my lines.
What does vaccum do for the regulator anyway? Increase / decrease?
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Old 08-26-2004, 02:09 PM   #7
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pressure regulator increases the pressure by 10psi when vacuum is absent.
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Old 08-27-2004, 08:52 AM   #8
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After owning several turbocharged cars, I made it part of my weekend routine to check all the vac lines, as they would also carry positive pressure under boost...which means lost boost if they went bad :( .

Speaking of turbo cars, I found a turbo Grand Prix just languishing here in the area. How common or rare are those?
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