Now this is only a well educated guess, and ultimately you will need a smog
check repair station to verify this hands-on, but with HC measurements that
high (700ppm) it seems your 1984 Fleetwood Southwind is suffering a misfire;
more then likely due to the ignition system. A misfire means your
motorhome's engine is not igniting all cylinders at the right time or
thoroughly enough. This is resulting in the production of high unburned fuel
(HC), and partially burned fuel (CO). Once the high HC fault is found and
fixed, CO should drop dramatically as well.
Begin by inspecting all the sparkplugs and their wires. If any of the plugs
look worn out or have excessive carbon build-up replace them immediately.
You may use any brand of product designed to work in your vehicle. The
distributor cap should also be inspected for cracks or excessive carbon
deposits. If it appears that the cap may be faulty, you will need to replace
it. More then likely you will see an instant performance increase and a drop
in HC once these corrections are made.
