I know its been awhile since anyone has posted. Here's what I ran into as we were driving 1988 Winnebago 454 Rochester carb.
We were slowly losing power and if I gave it more gas it stumble and popped out the carb. It progressively got worse the more we drove. On the orad we replaced the filter inside the battery tray, the filter in the carb, cap rotor and electronic ignition module.
The secondaries were not opening so I had to adjust the vacuum screw to allow the tab to pull something on the right side of the carb which was blocking he secondaries from opening. MOST importantly the vacuum advance on the distributor was stuck the vacuum part was fine from sitting the actual part that advances was not turning. A few screw driver shoves some wd and it started to move when vacuum was applied you can do it with a vacuum tool or just use your mouth you will get gas fumes in your lungs but when stuck on the road it does not matter, The plugs were in great shape and the wires were dry rotted literally falling apart. I was luck I had wire covers which prevented any side spark.
After completing all of the above it ran like new!! I think the key was the advance was stuck in the distributor and the filter was clogged. The carb was super clean when I took it apart so its not the carb. Can't be the little accelerator pump-- that would not cause a stumble, This all worked for me I think I could have cut it to carb filter and advance in distributor. No one mentioned that for all the stories I read.
Thanks!
