04 Turbo LE MPG decrease??

[tandt14]

Hello all! This is my first post. I usually lurk around the forums but I am having issues with my 04 turbo le auto. I've owned the car since 27k miles (it now has 42k miles on it). Around 33k miles I started having misfire and took it into the dealer--they replaced the plugs and wires and the problem was fixed. Then I started noticing the same problem developing around 39k miles...so I have my non-Chrysler mechanic replace my plugs and wires (NKG iridium plugs and AutoLite premium wires) and the problem stopped, again. Well, to my issue, the car pings under heavy acceleration-getting up to speed on the onramp to the interstate or even a hard accelleration at a red light. Around 38k miles I started noticing a sharp decrease in MPG...I used to average 21mpg, now I do good to get 18mpg under the same driving conditions. I used have tried 87, 89, and 91 octane in the car with the same mpg results.

My Cruiser is under powertrain warranty until 70k miles but will they warranty the work since I have put aftermarket plugs/wires on the car? Thanks for your time!

[tandt14]

Used $11 Chevron Fuel system cleaner. Still pings slightly under load but MPG back up to 21. I'm going to run another one through and see if that completely clears up the pinging. Hope that this helps someone else.