C4...1988...Service Engine Soon Warning

I'm getting the 'Service Engine Soon' light on my dash regularly...I only use the car for long trips to Florida 3 or 4 times a year...For these trips
the engine runs at 2000 to 2200 rpms for 10 to 11 hours...There's usually one fuel stop and a couple of personal pit stops along the way...The light would come on itermitently...On the most recent trip it was on for just about the entire trip...750 miles down and 750 miles back...The EGR valve and the O2 sensor were recently replaced (just before the last trip)...The catalytic converter was replaced about 4000 miles ago...the current mileage is within 200 miles of 150K...I try to use no-ethanol fuel when I can find it...Any light you could shed on the subject would be appreciated...TIA...Jeffyg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 5 Feb 2009 20:12:05 -0500, "Jeff Greenlaw"

Either get a code reader or get someone to read the codes. Lots of things cause the service engine soon light. Loose or bad gas cap is one item. Small vacumn leak.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Do you get any other lights in addition to the engine service? When it first started happening I got that light by itself, but pretty soon the DIC panel was lighting up like a Christmas tree and the engine took on a mind of its own. I ended up replacing the ECM.
AJM '93 40th Anniversary coupe, 6 sp (both tops)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Read the trouble codes. It can be done with a paperclip or by using a scan tool, which some autoparts stores have and will hook up for free. The light does not have to be on to read the code. It will remember the trouble code even if the light goes out.
The code does not necessarily indicate what component needs to be replaced, but it does get you started in the right direction for troubleshooting.
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.