Alternator causing idle surge issue??

[ivorton74]

I had a friend of mine replace my head gaskets a few days ago and the truck runs better than it ever did since I put it in back in 2014...but still having idle surging. The thing is when my buddy started the truck after he put everything back together he realized he forgot to hook up the little red wire behind the alternator...he said the truck started idling really good...then when he put that wire back on it started surging. Today I tried what he did and he was right. So could there be something wrong with my alternator? I believe the one in the truck is a 105amp and my buddy thinks maybe I should switch to a 130amp alternator...what do u guys think? I've been having this issue since I put the motor in and it's driving me crazy

[homemade87]

The difference is your loading the engine at idle when the alternator is charging.
There is no load when the alt is not charging . Turn on the a/c and it will probably do the same thing . You said when you put the engine in 2014 . What mods did you make . Sounds like your tune is off . If you made any changes the tune will also have to be change to compensate ( cold air , long tubes , cam , different intake , different throttle body just to name a few ) .

What you are experiencing is a by product of a tune not right . The computer is hunting at idle . Get it tuned and it should go away .

[ivorton74]

Truck is mostly stock aside from the short ram intake and fbody exhaust manifolds...doesnt have a/c. You're right though...i need to take it to get it tuned pretty soon

[BR3W CITY]

If the surging occurs but operation is otherwise normal, than its loading up and the tune isn't setup with enough iac/tps. (could also be the a/c loading up if you have it, its the same load principle to the belt drive).

If the surging happens and you get dimming, codes, stalling, fuel codes then you probably have a ground or charging system problem. This is more like what you'd experience when you have a vehicle running on alternator only (battery is a capacitor instead of a battery basically).

[ivorton74]

Forgot to mention it only surges with the engine is warm and is in Park...doesnt surge when in gear