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| 10 Hg Vacuum, Running Rich? | |
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| Tweet Topic Started: Sep 13 2012, 07:51 PM (851 Views) | |
| cnshealy | Sep 13 2012, 07:51 PM Post #1 |
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I have a 98 chevy metro 3 cy 5 sp. I did a compression test and everything was good. I don't see any vacuum line leaks. Power is down and mileage has dropped to 38 mpg. Are there any other things that can cause a loss of vacuum on this motor? Any suggestions will be appreciated. Thanks. |
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| evmetro | Sep 13 2012, 08:10 PM Post #2 |
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Blocked cat. |
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| evmetro | Sep 13 2012, 08:13 PM Post #3 |
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If it is your cat, you can get down on the ground and kick or slap it to see if it rattles, if you are not already hearing rattling sounds when you take off. Sounds kinda like a loose heat shield when it rattles. |
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| cnshealy | Sep 13 2012, 08:19 PM Post #4 |
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It is not a blocked cat. It came apart about 10,000 miles ago and was gutted. |
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| Memphis metro | Sep 13 2012, 08:29 PM Post #5 |
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Check your timing belt and marks. What do you call good compression numbers>? |
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| evmetro | Sep 13 2012, 08:29 PM Post #6 |
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I like to to spray starting fluid around the manifold and vaccum lines to check for leaks, but i suppose with the fire hazzard that this presents, I will not suggest this... |
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| evmetro | Sep 13 2012, 08:32 PM Post #7 |
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If your cat was gutted, was it because it was coming apart? If so, some of that crap could have blown downstream and plugged the resonator or the muffler. |
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| cnshealy | Sep 13 2012, 08:45 PM Post #8 |
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Compression numbers were all around 180. Cat did break apart. I can see through the resonator but I can't varify the muffler is good. |
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| Memphis metro | Sep 13 2012, 10:32 PM Post #9 |
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With compression numbers that high the vaccum numbers should normal as well. Not only will an exhaust restriction cause issues but a intake restriction can as well. |
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| iamgeo | Sep 13 2012, 10:51 PM Post #10 |
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Big League
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My '98 just started to throw a P0400 code the other day. Yesterday it was idling like crap and the vacuum gauge was at about 10hg and the needle was bouncing around, it was at just over 800 rpm. Give it a little gas and it smoothed right up. Looked under the hood and the EGR valve was fully pushed back. After I made a few deliveries it "fixed" itself. Although it still keeps throwing the code after I clear it. I have a vacuum gauge and a scangauge ll. That's how I know the CEL code and am able to clear it. Is yours doing anything I just described? |
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| fritzgeo | Sep 13 2012, 11:54 PM Post #11 |
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This could be your problem, check your fuel filter out see if she is gunked up, she could not be getting enough fuel into her, another thing to check for is your IAC(Idle Air control Valve) Or your Fast Idle Air Control valve. Look down your throttle body and see if its dirty! Whens the Last time you replaced your PCV Valve or spark plugs and wires? BTW if it turns out to be your fuel filter! your going to need to goto Oriley Auto to get it and its part number 33824 for a Wix filter if its the small skinny size. BTW if it was the Cat and if it was block the engine would of cut off. The best way to test the CAT is to remove the two bolts from the exhaust manifold and drop it and see if she runs better RPM or drop those bolts off and shake it and listen for rattles. Rarely its your CaT. But check all that and check your spark gap for .40 or 1.0mm |
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| evmetro | Sep 14 2012, 12:28 AM Post #12 |
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Maybe a rat was sleeping in you intake duct when you started it up. |
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| cnshealy | Sep 14 2012, 05:08 AM Post #13 |
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I have a scanguage II and it gets a P0400 code occasionally. The egr valve opens and closes as it is supposed to. I have cleaned the egr valve and passage ways recently. I don't think my metro has a fuel filter. I think chevrolet removed the filter when it took over in 1998. I am gonna replace all vacuum lines this weekend just to be sure that is not my problem. |
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| Shinrin | Sep 14 2012, 09:44 AM Post #14 |
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you can drop the exhaust from the manifold, two bolts, and see if the vacuum improves any. It'll run loud as crap, but you should be able to tell a difference if the problem is without the exhaust system. |
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| mwebb | Sep 15 2012, 09:39 PM Post #15 |
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FOG
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flutter in the intake vacuum at idle always equals valve train problem restricted exhaust should not cause flutter 10" of vacuum at idle with flutter with correct cam and base ign timing and compression of 180 psi on all cylinders is not plausible . place a dollar bill over the tail pipe when idling if the dollar bill is always puffed away , you are not misfiring if the dollar bill gets sucked into the tail pipe regularly there is misfire and i would bet one valve never opens or compression values above are not correct compression is useless anyway post cylinder leak down values Edited by mwebb, Sep 15 2012, 09:40 PM.
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