Hi William,

I doubt that poor gas quality is the issue. There is no difference when either Techron, Valvoline System Cleaner or an octane booster are used. I've also tried adding "Heat" to remove any water in the system. Again, no effect. The car always gets Chevron Supreme.

My guess is a sensor is failing (something key in maintaining the idle speed) or the fuel pressure isn't high enough. I haven't noticed any performance issues while driving the car and its highway performance is very strong. On recent trips, it has been averaging 25 to 26 mpg on the highway.

The car is headed for the dealer later this week to see what they come up with. So far, this is what has been done:

85k - Motors mounts & transmission mounts
90k - 90k service, replaced caps & rotors
95k - replaced wiring harness
- pulled the injectors and had them cleaned, seals replaced, etc.
- checked voltage at each cylinder (measured equally)
- checked alternator
- checked & re-hung exhaust (wasn't rubbing against anything)

I'd like hear what sensors should be checked & how the fuel system should be checked. I'm not concerned about the dealer not doing their job, I just want to know in advance a good strategy - otherwise, I'm just taking their word for it and that doesn't set too well with me.

Thanks for the help.