Alright my 03 6 speed has been making a spattering noise on start up after the car sits overnite. You mainly hear it thru the muffler and it goes away after the car runs for awhile. If I try to drive it when its sputtering it will hesitae. A few weeks ago when I was driving to the gym my cel started flashing but went away. Does this sound like a bad precat, 02 sensor, or something else. If its the precat my car is still under 80,000 miles so it should be covered under the 8/80 emissons warranty.....Any clues what the cause could be.

 

CEL Flashing is a definite misfire, I just recently had this on my car. I replaced all the plugs and one coil and problem solved. Misfire could be anything though, including the MAF, which could be why your car is hesitating. What I recommend is waiting till you get a solid code and check to see if its a specific misfire, or just a random, that will help you determine what to do. Changing the plugs wouldnt hurt though, definetly helped for me. Flashing CEL is a warning that the severe misfire could eventually cause clogged cats. Good Luck! keep us updated

 

Yeah that's what I was wanting to do. See if I get a perment CEL and check the code, but I don't wanna kill my precat or worst wait till I am out of warranty if it is the precat. I will probably do all the plugs, coils, and new front and rear valve covers first and take it from there.