Rough Idle 267 4.4L V8

[Monte1981]

My 1981 Chevy Monte Carlo has been running very rough when idling. When I put it in drive it gets a lot worse, but at high rpm it is smooth. I’ve just replaced all of the spark plugs yesterday and it was running smoother than ever. The engine has 72,000km on it and has brand new oil, air and fuel filters. Any advice would be appreciated greatly!

 

[pontiacgp]

what did the plugs that you removed looked like? Does it idle rough cold or at operating temperature

 

[Monte1981]

the plugs looked really good for their age, no oil or liquid on the electrodes. The idle is rough cold and when it’s warmed up. I did find a very small crack in one of the electrodes of the new spark plug I put in, do you think that has any relevance?

 

[79 USA 1]

Personally I would check for a cracked , weathered or broken vacuum lines. Replace the cracked plug and check the condition of the plug wires and the distributor cap. Just my $.02.

 

[pontiacgp]

the plugs looked really good for their age, no oil or liquid on the electrodes. The idle is rough cold and when it’s warmed up. I did find a very small crack in one of the electrodes of the new spark plug I put in, do you think that has any relevance?

change that plug cause that could be the cause of the rough idle

 

[Ribbedroof]

Plug wires as mentioned above. If they're the stock type/routing, the replacements available aren't nearly as good as they used to be.

 

[1320John$$$]

Do a cylinder drop test using your test light to find if it’s missing