78 235 johnson idle problem, ignition?

[jy118lfd]

78 235tl johnson. It idles ok except every few seconds it seems to miss and sneezes it will make it stall at an idle. above idle it still does it but is running faster so it does not stall. I tried to spray some premix in each carb to see if extra fuel would help but no change with. I have ten years as a master tech with auto engines and this seems to me to be an ignition problem. I have a different timer base on the way and will try that. P.S. it has new coils on all six cylinders and grounds are clean. carbs were rebuilt and two new power packs

 

[Walker]

Re: 78 235 johnson idle problem, ignition?

Sneezing is an indication of a lean condition. I would pull the plug wires one at a time to try to isolate which cylinder or cylinders is sneezing. Then open up the idle needle on the corresponding carb, I believe that engine has adjustably idle needles. A good carb cleaning overhaul may be in order too.

 

[jy118lfd]

Re: 78 235 johnson idle problem, ignition?

Thanks I have gone through the carbs. I am going to try to isolate the cyl. The carbs have fixed idle jets and the only way to change the mixture is to drill or replace the jet

 

[OBJ]

Re: 78 235 johnson idle problem, ignition?

Jon...if you have a service manual for the engine, run through the sync and link. This puts the timing in time with the throttle plate opening. Also check that all the throttle plates are opening and closing at the same time. This is also part of the sync and link procedure.

 

[jy118lfd]

Re: 78 235 johnson idle problem, ignition?

Will try the sync and link. Just replaced the nylon bushings on the link from the throttle and timer base