85 Mercury Marquis Shaking During Idle

I have a 1985 Mercury Marquis and just last night it started shaking violently when I started it and when it idles. Although it doesnt shake when I give it gas, it runs more roughly now.
All fluids are good.
My mech cant see me until Tuesday, earliest - is this a serious-die-and-leave-me-on-the-side-of-the-road thing?
Thanks
--
Posted using the http://www.autoforumz.com interface, at author's request
Articles individually checked for conformance to usenet standards
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Could be vacuum leak, EGR valve that won't close properly, bad plug wire, or a couple dozen other reasons. The first step is to read the stored trouble codes and run on-demand diagnostics. A five minute affair, which on your '85 can be performed with such sophisticated tools as a test light and a paper clip (I am assuming that yours is the domestic, throttle-body injected engine, not the carbureted export model). This would at least give some clues. Doubt that at this point anyone could tell you how serious this is and whether it will leave you stranded. Let us know what your mechanic found.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hope they figured out your shaking problem by now. As a former owner of one of those and a current owner of an '85 LTD (same thing, except for the grill), I am just curious about your car. Is this really a Marquis, or the 'Grand' (Crown Vic's twin)? The common V6, 3.8L liter engine or something else? Is this the original engine? How many miles? Oil consumption? Transmission still shifting properly? (or perhaps your is manual...)Everything else still working (A/C, electric windows, etc)?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"ShadowWolf" wrote

EGR valve stuck partly open by carbon deposits? The valve should be on the back of the manifold, with a flying-saucer shaped vacuum diaphragm on top of it. While the engine is still cold, see if you can get your fingers under the edge and work the diaphragm/valve stem up and down a few times.
It could also just be a vacuum leak. Any strange hissing from under the hood? Any vacuum hoses that have split or come unhooked?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I vote for the EGR too. I used to keep a few feet of vacuum line in the car at all times for my '84. I would attach it to the egr, then suck on the other end to open the valve a few times with the engine running. The hose needs to be long enough so you can reach the throttle lever and keep the revs up while you operate the valve.
PoD

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.