Rough idle

[martingmc86]

I have an 86 GMC Sierra 5.0 I’ve noticed it idles kind of rough when stopped I replaced the spark plug to some acdelco rapid fires#1

 

[squaredeal91]

Im guessing its tbi? While engine running unplug coolant temperature sensor and see if it runs better [considering it don't die right away lol]

 

[gmbellew]

Im guessing its tbi? While engine running unplug coolant temperature sensor and see if it runs better [considering it don't die right away lol]

an 86 should be carb if still stock

 

[martingmc86]

It’s broken and I can’t find the correct one

Im guessing its tbi? While engine running unplug coolant temperature sensor and see if it runs better [considering it don't die right away lol]

 

[martingmc86]

an 86 should be carb if still stock

Yes it’s it’s 100% stock with a brand new original carb I found a carb 0 miles from a GM plant that was throwing away new parts

 

[squaredeal91]

Have you checked cap and rotor?

 

[martingmc86]

Have you checked cap and rotor?

I replaced it like 12k miles ago

 

[squaredeal91]

Is it running rich? Loading up?

 

[martingmc86]

Is it running rich? Loading up?

I tried adjusting the air/fuel mix screws it felt better but I still feeling a little rough I did a vacuum smoke test and no leaks detected

 

[squaredeal91]

Does it still have cat? Any exhaust leaks?

 

[martingmc86]

Does it still have cat? Any exhaust leaks?

Yes still does original ones Im not sure of any exhaust leaks only the cat does look like it might have a leak when I hit it with a rubber hammer it releases dust in the middle of the cat