Smoking and chop at idle

[Jeffthe620]

Hey everyone, 

I just recently pulled my truck out of the garage after about 2-1/2 months of working on it and it’s started up just fine and runs good, but when it idles it chops like it has a cam (it does not) and lightly smokes a white/blue color. Any ideas what’s wrong? 

[datzenmike]

Black exhaust is too rich as in the choke on

 

Blue exhaust is incomplete burning of oil. Possibly worn valve guide seals or worn rings. May smoke if sitting a long time and oil has more time to run down the worn valve seals. Depending on amount of wear it may burn off in a short while and not be noticeable. In extreme oil burning conditions the smoke can appear white.

 

White is usually steam from coolant leak, usually a head gasket. This would explain the poor idle also. Let it run or better, take for a drive. If it over heats or shows a coolant loss then this is your answer.

[Jeffthe620]

Thank you mike, I’ll take it on a drive ASAP.

how hard is a new head gasket on a L20B? 

[datzenmike]

Last one I did was $30 CDN at NAPA and a morning to change. Make sure you know how to properly block the timing chain tensioner so it can't possibly pop out or add another 4-6 hours to fix and a timing gasket set.

 

First, make sure it's is a blown gasket. Smoke can have several causes that are not blown head gaskets.

[Jeffthe620]

Thanks for the info, it seems like it might be one of the many problems but I’m going to try to run some tests today