1986 5.0 gt idle problems

[catillac]

My beast from a cold start will have a idle that jumps up and down then stall 3 or 4 times till it warms up. I replaced the idle air control motor and cleaned out the trottle body but with no luck it still does it. I'm not sure what to do next can someone maybe give me some pointers on what i should do next. Thank you very much!

 

[ThePumpkin]

Sounds like a vacuum leak. I assume it goes away when the engine warms up? do you have any modifications on the engine?

 

[catillac]

Yes when it warms up the idle is very nice. Runs great! There is a NOS set up thats been put in but i have never used it i was going to take it out but i started to have this problem. Maybe the two are related somehow.

 

[ShallowGrave]

Check the various small vaccuum lines in the area of the EGR valve. I had 1 leak I could hear, and one I only found by grabbing the connections. Fixing the leaks fixed my idle & small backfire problem.

 

[v8only]

are you sure it's a beast??? Last time i've owned an 86, which is currently, it wasn't the "beast" model