Acceleration Issues - Shutters and Sputters

OK, lets see if I can explain this. I have a '68 with a 289, 2100 2 barrel carb, C4 automatic transmission. Lately I've been having a problem with acceleration, now here are the details.

This problem happens in cool weather or hot weather, engine cool or hot. When I punch the gas the car gives kind of a shutter and sputter. Some times threatens to stall but usually only when it's cold. It appears to do this only when I let off the gas in traffic for 5 seconds or so or come to a stop and then go, or if I give it gas release, gas release, gas release and then hit it. It is hard to tell if it gears down because of the shutter. But, when I hit the gas it will sputter and shutter for a while (length of time varies) then clear up and run normal or if when it occurs I release the gas and slowly go again it's fine. If I apply the gas slowly it goes fine. All other times the engine runs great with the exception of an occasionaly miss. I have also experinced starting problems since this problem appeared. If it sits about 10 minutes it some times won't fire turns over fine, after I let it sit for 45 minutes it starts. If it sits for a couble of minutes starts fine or a couple of hours starts fine. Not sure if these problems are related. This does it in all gears but not in park or nuteral.

I have replaced the distributor cap, coil, coil wire and rotor with spare ones on hand, same problem. Checked timing, good. Carb is getting fuel, choke seems to be working properly. I have replaced some of the wiring under the hood because the old ones where old, brittle and breaking. I beleive this might have all started after I cleaned the carb with carb cleaner, but not sure. The temp gauge reads higher then I would like to see, but that should not affect the cool conditions.

I was thinking plugs and condensor, but the car runs and starts fine most of the time. I extended my metal fuel line away from the hot engine by about 4 inches to solve a prior vapor lock. Might this be a nother form of vapor lock? There is a slight kink in the water by pass hose but not significant enough the restrict the flow of water.

Any thoughts as to where to turn my attention to? I was thinking the carb should be rebuilt eventually because it appears very original.

Thanks

Sounds like you need a carburetor rebuild. Go to anywhere that sells carb kits and they will sell you the kit. Read through the whole kit instructions carefully 3 or 4 times, and make sure that you understand everything it asks you to do, and especially follow the cautions, as not to use carb cleaner on the bimetallic pieces. If you sprayed carb cleaner on it and it started acting up, that means you either moved something around in there and lodged some gunk in there, or you moved some gunk that was plugging some kind of leak or something and now there's a hole somewhere that's not supposed to be there. If the carb hasn't been rebuilt, it never hurt ANYTHING to change those gaskets and needle/seat. Also, it will give you a highly detailed list of in-carb adjustments and you'll be runnin' sweet. Good luck!

Sounds like a bad accelerator pump. Time carb for a rebuild as stated.


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1966 Stang Coupe Org. 6 cyl. 351w,Sealed Power Hypers, ARP bolts,Total Seal rings,Eagle H-beams rods,Balanced,Hedman long tubes, Pro Comp 2.05/1.60 Heads, Shaft roller Rockers, Victor Jr intake, Holley 750 DP, Ed Nix Custom .600/.600 254/258 @.050 Solid Cam, Crane solid roller lifters,Richmond 4.11, Strange mini spool, Modified C4, 3500 stall, Redneck Transbrake, B&M Hammer shifter, Shelby lowered, Pro Comp 6Al system. Mickey Thompson 275/50 Et Street Drag radials.

<font size=-1>[ This Message was edited by: forthman on 8/19/06 2:20am ]</font>

Thanks for the input. I do plan on a carb rebuild here soon.

But in the mean time for the hell of it I decided to pull the plugs just to see. Cylinders 2, 5, 6, 7 &amp; 8 had some carbon build up but not bad. Cylinders 1, 3 &amp; 4 had some white ash deposits again not bad. So I cleaned and regapped since they weren't that bad I decided to check the points while the engine was still cold. To my surprise there was no gap, cleaned and regapped the points. She fired right up, checked the timing and set to specs took her for a drive. So far so good no shutter or sputter. I'll have to wait and see if the problem returns after some more driving. If it does I'll pull and recheck the plugs and see if they got fouled again to induce this problem. Which would mean a carb rebuild. I do know it is running rich because it will diesel and sputter abit before shut down.

Thanks again you guys rock.[img]/forums/images/smiles/icon_bow.gif[/img]