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#1
07-18-2007, 08:16 AM
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Vacuum help
I am looking at the suction on my vacuum system, and I am getting around 7-8 in/hg at idle, but dropping to zero when I am accelerating. What could cause this?
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#2
07-18-2007, 12:41 PM
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What model? Vacuum should be much higher at idle, if a gasser, but under acceleration it would be very low - not a good test point.
Steve
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'91 MB 190E 2.3 '08 RAV4 Ltd 3.5 '83 Lazy Daze m'home 5.7
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#3
07-18-2007, 02:16 PM
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Do you have lack of power ? On park, can you rev up the rpm beyond 5500 rpm without flooring the pedal, smoothly without hesitations ?
If this is at the intake manifold, yes the vaccum at idle is very low, should be between 16 and 22 inch Hg. Two possibilities: 1. EGR valve is malfunctioning, it should be closed at idle but is instead open. The vaccum level at the EGR valve connection should be lower than 2 inch Hg at idle, and about 4-6 inch Hg when the engine is at 2000 rpm. 2. You have a clog in the exhaust system, most likely the catalytic converter. Either disconnect the cat converter at the coupling with the exhaust manifold OR disconnect the manifold from the engine to test.
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Saumil S. Patel
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#4
07-18-2007, 02:26 PM
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We need to know what model/year. Please update your sig so we can help. If a diesel, it sounds like your vacuum control valve needs adjusted/replaced.
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1989 300E 144K
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#5
07-19-2007, 06:25 AM
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I have an '85 300CD. I posted in the diesel section too, but didn't get a response.
I tore a bunch of the vacuum system apart yesterday, and it was all messed up. I have no idea what the guy was thinking the last time it was put together. I did find a few connectors with slow leaks, I am waiting to get some new ones...hopefully today. I also hooked the mightyvac up to the main vacuum line, and it was pretty steady at 16 in/hg with or without gas. once I started hooking things up to the main line, it started twitching when I gave it fuel. Sometimes it would drop when revving, sometimes not.
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#6
07-19-2007, 10:39 PM
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Vaccum drop during accel is normal because air is entering the intake system. And a diesel does not produce a lot of vaccum at the intake, so your vaccum levels may be o.k., someone else who knows diesel better should help you out.
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Saumil S. Patel
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