well if your comfortable with sacrificing your oil change i would highly recommend sea foam (1/3 in your gas, 1/3 in your oil and 1/3 in your air intake)
I have a 99 3.8l Mustang first off oil is topped up just had an oil change, Oil pressure is normal, Check engine light is not on.
When the car is idleing in Neutral or Park there is no rattle even when reving the motor. But when I put the car in drive it begins a rattle durring acceleration and increases in speed with the rpm.
I noticed this about 2 weeks ago, it is getting worse It sounds like it may be a valve lifter any help would be great.
The rattle is not there all the time only during a steady pace under 70km and during acceleration The noise goes away once up to speed. No exhaust leaks either. It is coming from the Driver side valve cover area it seems to be. Also there seems to be a miss to the car as well. all spark plugs are new. could a faulty wire cause a rattle?