1. Check for stored fault codes, see the sticky about the key dance to read them out on the EVIC.
2. Check all your "periodic maintenance items", some people still call it "tune-up" items, if you are due soon or overdue, these things cause poor idle. Like Spark Plugs, Ignition Cables, Air Filters, PCV Valves.
3. Put some Fuel Injector Cleaner in the Tank, I've "heard" Chevron, with "Techron" is the best at cleaning the injectors.
EGR, check it, I've had bad EGR's cause my idle to surge up and down, but it did it warm and cold. Plus, some engines don't have an EGR and the Commander engines very well might NOT have an EGR.
AFA non-OEM Spark Plugs. The new DIS (Distributorless Ignition Systems) can do some funky things, like share 2 plugs between one coil, and run one of the two plugs with reverse current. As well, they can be more sensative. The recommended plugs are the ones that have been tested with your engine and proven to work. NOT necessarily does that mean other plugs won't work as well, but if they are NOT recommended, then you just don't know.
Using Single Platinum/Iridium plugs with an ignition system that uses reverse current on half the plugs, you reverse anode and cathode on that plug. The whole reason Single Platinum/Iridium plugs last longer is because the harder metal on one electrode cause less metal tranfer during use. You reverse that, then you have faster metal transfer from the softer metal eltrode to the harder.
The Double Platinum Plug makers have all sorts of literature describing this and state this is exactly why they created double platinum plugs, i.e. platinum on both eletrodes, for the plugs that have reverse current flowing through them.
If I was having idle problems, and used something other than the recommended spark plugs, I'd switch back to the recommended plugs and see if that fixes it. It often does, but keep in mind, more than bad plugs can cause idle problems.
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Last edited by Mongo; 09-15-2011 at 03:17 PM.