ibyron

So my car jerks around 35-45 mpg so i thought maybe it might be a bad spark plug so i decided to change them.. well first of all it still jerks, second my car idles now when its on drive or reverse, it seems to have lost power and 4th theres a huge loss of miles per gallon... maybe i installed spark plugs wrong or theres a bad spark plug? Any idea what it can be? Oh and the Car is a 2000 mustang gt automatic

mustangman02232

How were the coils/coil boots?

Csrt4to5.0gt

Are they gapped properly? Maybe a tip is broken. I don't remember if those years were coil on plug or distributor/rotor setup but check those things along with the spark plug wires, too.

mustangman02232

99 up is coil on plug

ibyron

I checked them out yesterday abd it idles alot less the coils and wires looks good and even the spark plugs.. how tight are the spark plugs suppose to be?

Csrt4to5.0gt

You tighten them kind of the same way as an oil filer. Just barely past hand tight. Make you use anti seize on the plugs, too. Are they gapped properly? You could also have a bad/dirty mass airflow sensor, too.