76 Comet 3.3L. Got it running as it was having issues turning over. Now that I can get it to turn over it seems to loop at idle. When I apply a little gas this loop goes away. I thought at first it just needed to warm up. But the loop at normal idle doesn't go away. Not sure if the carb needs rebuilt, or the idler screw needs adjusted, or what. Ive heard the inline 6 has idle issues. Anyone else had this problem?
DocRoche, are you indicating that adjusting the carburetor is beyond your level of automotive expertise? If not, why not attempt an adjustment?
I've never done it, but I'm sure its not to difficult. I was just wondering if anyone had any idea of what would cause the surging.
Surging can be caused by either heavy fuel loading or excessive lean out. If you suddenly crack the throttle and it "clears out its lungs"/puffs even a tiny bit of smoke then you are probably rich. Considering the retarded timing curves most people are mistakenly running(stock cam or not), I would guess it's more likely to be rich condition than lean one. Retarded timing also fouls plugs quicker and adds more unnecessary cooling system heat at idle/light cruise. Tuning idle mixture screws is one of the easier things to do when it comes to tuning a car up. Simply connect a vacuum gauge to full manifold source and tune for highest.. and more importantly.. the most consistent reading. IOW, if you can reach 19" of manifold vacuum at peak reading but it drops/fluctuates down closer to 18"?.. then it may be better to scrub off some of the peak vacuum capability and accept a more consistent reading of 18" to stabilize the AFR. Unless you check the engines tune almost weekly, pulling back just short of optimized settings(fuel or ignition) gives more margin and helps the motor "hold its tune" for longer periods of time too. You'll also need a timing light to avoid chasing you tail around while tuning the carb. If the timing is not even remotely optimized?.. and it most definitely isn't if you are running the vac advance pot to a ported vacuum source(allows zero help at idle/high idle compared to full manifold vacuum source), then the carbs more idealized settings will NEVER be achieved. Ignition timing and fuel curve settings run hand in hand. So much so in fact that changing one then causes the bullseye to suddenly move around for the other. Which is why you need to go back and forth between the two several times over before it can be dialed in more closely to what the motor actually wants.
Could be the ethanol in our "modern" gasoline, I know it wreaks havoc on my mowers. One does this same thing, I can add a pinch of choke and it smooths right out. The governor catches it when it's loaded, but idling or light loads is another story. Prolly the internal passages are getting smaller because the crud in the gas is depositing on the insides. Try a little choke, if you don't have one, you can remove the air cleaner and slide a piece of cardboard partially over the carb throat...
