1995 Chevy Blazer Low Vacuum

Tiny
95BLAZERRICH
  • MEMBER
  • 1995 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 188,000 MILES
I have a 95 chevy blazer 4.3 engine code W I have replaced the fuel pump, the cat, and the muffler I have checked for vacuum leaks and done a smke test on the vacuum hoses. The truck losses all vacuum under accelleration. With a vacuum gauge it has 24 inches of vacuum at idle and under a load going up a hill it will drop to 5 inches. I do not know were else to look for this problem can you help please. Thank you Richard Mitchell
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Saturday, July 3rd, 2010 AT 6:21 PM

5 Replies

Tiny
RASMATAZ
  • MEMBER
Check the exhaust system for an excessive backpressure-could be a problem with the catalytic converter
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Saturday, July 3rd, 2010 AT 6:27 PM
Tiny
95BLAZERRICH
  • MEMBER
Thank you for the sugestion. The catalytic converter, the muffler and the tail pipes are just a few days old.
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Saturday, July 3rd, 2010 AT 6:57 PM
Tiny
RASMATAZ
  • MEMBER
ENGINE STATE VACUUM GAUGE READING INDICATION
Steady idle (800-1200rpm) Gauge steady, 17-22 Normal & healthy

Steady idle (800-1200 rpm) Intermittently drops several needle divisions Sticking valve or broken valve spring

Steady idle (800-1200 rpm) Steady, low reading, 8-14 Small vacuum leak or valve timing off; could have low compression/worn rings (verify with a compression or leakdown test).

Steady idle (800-1200 rpm) Steady, low reading, under 8 Vacuum leak (check brake booster, vacuum lines, etc.)

Idle (800-1200 rpm) Needle drops sharply on a regular rhythm Burnt valve, or a valve with clearance too tight

Idle (800-1200 rpm) Needle drifts up & down, along with rpm drift Mixture off or small vacuum leak

Idle (800-1200rpm) Vacuum gradually drops Excessive exhaust back pressure (plugged muffler or catalytic converter)

Idle (800-1200rpm) Intermittent fluctuation Ignition miss; sticking valve

Idle (800-1200rpm) Steady, above 22 Ignition timing may be too advanced
Open & close throttle quickly Drops to about 2, jumps to about 25 Healthy engine
Open & close throttle quickly Drops to 0, jumps to about 20 May confirm worn rings (especially if idle shows only about 15-20) Verify with a compression or leakdown test.
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Sunday, July 4th, 2010 AT 3:35 AM
Tiny
95BLAZERRICH
  • MEMBER
Thank you. From what the vacuum gauge is showing the motor is healthy. At idle wich is at 700 rpm I have a steady 22 inches of vacuum. Open to close it drops to about 4 inches and jumps back to about 25 inches. What is happening is under a load climing a long hill at 60 mph the vacuum will drop off and the A/C will blow from the defrosters and the floor instead of the vents. As soon as the hill is cleared the A/C comes back to the vents. I was driving the truck and out of no were it had a rough idle for a minute and all of this started. Can a bad egr valve cause this? The truck has also had a slight drop in performance and fuel milage. Thank you for all the help
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Sunday, July 4th, 2010 AT 5:28 AM
Tiny
FIXITMR
  • MEMBER
What was it?
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Monday, March 19th, 2012 AT 1:47 AM

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