99 Yukon engine misfire

1999 GMC Yukon 94000k 350
I am getting a misfire code on #5 cyl, The rep. said to rebuild or replace engine. Was a little reluctant on doing that so I ask for a compression test to
be done. They said that would be $120 so I said OK.. No. 5 was 140lbs and adjoining cyls was 150. I asked what the dif was between the wet and dry and he didnt know what I was talking about. After several calls he got with the mech. and he said they done wet/dry on #5 with no diff. also a leak down test showed it was bad rings. With these responses I dont know how good of a job was done on the tests. I replaced the plugs and the light goes off for a while and then on for a while. My biggest question is how to rule out other possible problems before moving on to the bad rings. Such items as EGR valve, bad ignition, fuel, etc.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You probably should try a GMC or Chevy group.
The Yukon is not made by Ford.
Jeff

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

first, if 150 is good, 140 is not bad, second, they said no diff between wet and dry-that means good rings, sounds like they didnt do it wet because it would show a diff unless it was a valve if there was a problem, But, if there was a valve problem it wouldn't have 140, much lower. Since you can change plugs you can do a compression test. You can get a tester for about $40. I would bet its a plug wire or coil if its got one for every plug. It could even be an injector thats bad. Can you feel the miss or does the light just come on?
Oh, this is a Ford group. Never stops the politics, so why the Chevys I guess:)
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.