Great mechanics!! HELP please!!

[Gcolladay]

The engine light came on in my 2003 ls8 ,last week.I've got 97k on it w/out any major problems.I took it to a guy who regularly works on ls.he said the d coil came up as bad.he replaced it but its still sending the same code.He than took it back off and put the old one back on and it ran fine.Now the light won't go off and it runs great one day then like :q:q:q:q the next!? rhe mechanic told me it might be the computer has gone bad.but to find out it was gonna cost me 250 bucks for diagnostics....needless I didn't go with it ....anyone got any Ideas? its so strange cause it runs fine some days then like crap......

 

[Quik LS]

sounds like you mechanic is lost.

Bad coils are very common issue with the LS. They either go out or they fail with oil leaking into the plug wells (the valve cover gaskets were re-designed in late 2002 - but some early 03's have the bad ones).