Hello all

[Montync]

I am new to the forums and this is my first post, so bear with me and guide me where I need to go. I have a 1986 C10 with a modified 305, from what I know it has
601 heads
I Think .204/.214-.420/.443 cam 112 lobe SA
performer intake
stock Edelbrock 1406 electric choke.
I have searched all over with no luck. The issue I am having is today out of the blue, I feel like I am getting a miss on one cylinder only at idle. All plugs are firing,tested for vacuum leaks, Nada! Here is the kicker I turn the the idle mixture screw on the Right, engine stalls(Normal)...
Turn the one on the Left, and the idle increases when turned clockwise, decreases and stalls counter clockwise.

I am leaning towards a blocked idle mixture bleed tube/circuit (as it is the next cheapest thing to check but need shop air to blast it clean)

Thanks, Look forward to many more head scratching moments with yall....

[rollin thunder]

I would try cleaning the carb out. On my eddy at idle it ran so rough I thought it was a miss. took it apart cleaned it all out and put it back together worked like a charm! This is from my experience (i am by no means a carb expert) definitely check all vacuum lines. make sure not cracked or torn and if the wrong kind of hose is on there sometimes it could collapse. Ive only seen it once.

[Montync]

Thanks thunder, I will try and rebuild it this weekend if it continues. All the lines are new/reinforced hoses, learned that the hard way with the egr and vacuum advance lines, they were so thin that the collapsed .

[rollin thunder]

no problem hope it helps and you get it figured out. and you should throw up some pictures of the truck when you get a chance

[Montync]

Well it was partially a clogged idle circuit system (I can adjust the Idle mixture screws)... Blew it out with compressed air, fired it up and ran great.....then the miss came back.... Changed the fuel filter for a clear one as a new filter was my last hope and the gas is milky colored and after sitting has water floating in it...Bad gas from a new gas station that just opened up.... good thing I only have a quarter of a tank

[rollin thunder]

glad you got the culprit! good straight looking truck and pretty engine!

[Desert1957]

Is this a Blower Drive Pulley I see?



Desert

[Montync]

@ Desert1957 It is a gilmer belt drive made by procomp.

As for my truck I have fresh gas, and the miss at idle is gone but when warm and driving down the road anytime I get around 1500-1700 it acts like it has a miss but you hear no change in the exhaust note.... It feels like this:
vroooooommmmmmmm..uga(fraction of a second)...vrooooommmmmmm.uga-uga....vrooooommmmm...once over 1700 It goes away, Buddy of mine says its a lean surge, why would it only do it in that rpm range? I am breaking down the carb and rebuilding it tomorrow... my only guess is whatever clogged the air bleeds may have clogged one of the air bleeds in the primaries this in turn gives enough fuel for idle?!..but not part throttle

Once I find the dang Gremlin that lives in my truck...Im taping him to the belt and letting the fan take care of the rest of him @ 5000 rpm

[rollin thunder]

Originally Posted by Montync

@ Desert1957 It is a gilmer belt drive made by procomp.

As for my truck I have fresh gas, and the miss at idle is gone but when warm and driving down the road anytime I get around 1500-1700 it acts like it has a miss but you hear no change in the exhaust note.... It feels like this:
vroooooommmmmmmm..uga(fraction of a second)...vrooooommmmmmm.uga-uga....vrooooommmmm...once over 1700 It goes away, Buddy of mine says its a lean surge, why would it only do it in that rpm range? I am breaking down the carb and rebuilding it tomorrow... my only guess is whatever clogged the air bleeds may have clogged one of the air bleeds in the primaries this in turn gives enough fuel for idle?!..but not part throttle

Once I find the dang Gremlin that lives in my truck...Im taping him to the belt and letting the fan take care of the rest of him @ 5000 rpm

Yes I can definitely see whatever clogged up the air bleeds could clog up other carburetor components. hopefully its the cause.

[Montync]

Well the carburetor was dirty..I am surprised it even ran at all. *some yahoo forgot to put a filter for the needle seat on at the factory, combined with a faulty filter make a heck of a mess. my float measured 13/16 inverted and the float drop was past an 1 inch and a half. I rebuilt it and I have to find a vacuum gauge to readjust my setting, plus the gas gave me a massive headache..... I will test drive it tomorrow.... and post an update

[Montync]

Well... rebuilt the carb. When cold she is fine but once warmed up the the idle is rough and at part throttle it is missing again... I am at a loss.

[Montync]

Well avoid cheap gas....%80 of the time it will be bad gas(not really but thats what it feels like)....half a liter of water in the gas tank.... Here is what I did

-I re-adjusted my valves and stepped up the timing to 16 initial, gave me better low-end/ idle but still had issues
-With the trash that made it to my carb, I had help to drain the tank...to my surprise a half a liter of water and a greyish/reddish sludge about a quarter of an inch thick
Refilled the tank with pure-non ethanol gas, no miss or stumble at idle anymore and pulls strong (Idle Fixed)
-An old timer with experience with carters and edelbrock told me the part throttle miss was due to the cam being bigger than stock, I needed to change the step-up spring which is actuated by vacuum...

Hopefully this helps anyone who might have issues....

I still dont see how there was so much water....