Hey there. Have a vt commodore that is running real ruff at idle but seems fine as soon as I start driving. It has over heated once but have put seal up in and tested head s and all good. Has been running rough for a long time now. Are plugs and leads a good thing to try. Also there is no vaccum leaks.
If what you say about the leads, plugs and vacuum is correct, look at a faulty coil pack, check fuel pressure and run a scan to see if there are any unresolved fault codes, start here.
November, 15, 2012 AT 1:15 PM
Had a similar problem with my VN Lexcen 3.6 V6,
Rough Idle, and apparently mediocre performance.
- Replaced plugs
- Replaced Leads
- Replaced crank angle sensor
- Did A/B swap of coils with known good one
- Replaced fuel filter
Solution was to replace the injectors - set cost me $145 off the Internet. Result was quiet idle, better performance all round. It felt like a new car.
The ultimate cause of the problem was that my daughter had run the fuel tank dry and the fuel system had picked up all manner of crud from the dregs in the tank. The fuel filter had failed and the original injectors were almost totally clogged. It was cost effective to replace the injectors rather than have them prefessionally serviced.