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  #1  
Old 02-01-2012, 11:30 PM
Fulcrum525's Avatar
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Exhaust causing truck to shake?/Clogged exhaust?

The Gwagen is throwing us another head scratcher.

Ever since we got the truck running we noticed that it would shake quite badly at idle. This shaking could be made worse if you lowered the RPMs all the way down. The shaking would always go away under throttle.

I assumed that the engine mounts were bad until earlier this week. We pulled the useless EGR off the truck and (Surprisingly) the shaking at idle stopped. We plugged the intake manifold and the exhaust manifold.

Here is where things get odd. Today my father took it out and while driving down a hill in a lower gear (3rd I believe) it expelled the exhaust manifold plug. (Copper pressure fitting but it was in tight)


My question is this- Exhaust, like any other gas or fluid, takes the path of least resistance. So why would the plug be shot out as opposed to the exhaust just making it's way through the pipes? Clogged muffler perhaps?

(Engine is a 617 naturally aspirated)
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Old 02-02-2012, 12:09 AM
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The muffler could be clogged. Is there an easy spot to disconnect the exhaust up front? If so you can do the shop vac test... unhook the exhaust from the engine, and attach a shop vac to the tailpipe. The tone of the shop vac shouldn't go up much... if it does there's a restriction.

-J
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Old 02-02-2012, 12:12 AM
Fulcrum525's Avatar
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Quote:
Originally Posted by compu_85 View Post
The muffler could be clogged. Is there an easy spot to disconnect the exhaust up front? If so you can do the shop vac test... unhook the exhaust from the engine, and attach a shop vac to the tailpipe. The tone of the shop vac shouldn't go up much... if it does there's a restriction.

-J

haha damn, we already put another replacement plug in a few hours ago. (Sure was fun driving it when it was that loud )

I'll have to double check but I think there is a connection at the bottom of the down-pipe.
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1982 300GD Carmine Red (DB3535) Cabriolet FOR SALE
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."
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  #4  
Old 02-02-2012, 03:22 AM
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been there done that - and yes your exhaust is clogged - my car's cat convertor was completely blocked to the point that it would not even rev past 2000 rpm and shutdown due to excess crankcase pressure.

a simple check is that the EGR should not be blowing smoke if its forced open at idle speed.

If you remove the front pipe and check you will find that the engine will behave perfect.
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Old 02-02-2012, 08:16 AM
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Originally Posted by Zulfiqar View Post
been there done that - and yes your exhaust is clogged - my car's cat convertor was completely blocked to the point that it would not even rev past 2000 rpm and shutdown due to excess crankcase pressure.

a simple check is that the EGR should not be blowing smoke if its forced open at idle speed.

If you remove the front pipe and check you will find that the engine will behave perfect.

Well too late to check the EGR as it's gone but I seem to remember seeing a bit of smoke coming out of the intake side......


Great something else to deal with now . Please tell me there is a simpler (Read cheaper) fix then having to replace the entire exhaust......
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1982 300GD Carmine Red (DB3535) Cabriolet FOR SALE
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