fouled plugs

My son's 90 Lumina with a 3.1 engine has developed a miss. We pulled all the plugs and found #3 and #5 plugs were carboned up. Replaced the plugs along with sparkplug wires and it still has the miss. Normally I
would do a compression check next, however my compression tester is unavailable for a few days. Is there anything else I can check while I wait for my tester? Thanks for your help Dale
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

1. Is only one cylinder missing? 2. Are multiple cylinders missing? 3. Are random cylinders missing?
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Steve Mackie wrote:

1. NO 2. YES 3. NO
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Excellent, which cylinders are missing?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Have you checked for spark?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A cheap spark plug tester can be very helpful in wringing out problems like this. If you dont have equivalent spark on the fouling plugs, then clearly you have to back up into the ignition system
#3 and #5 are next to each other, arent they?
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.