Pontiac Optima Engine is shaking, pulsating or vibrating Inspection at your home or office.

Common reasons for this to happen:

Most often, one of the following components is at fault:

• Old and worn spark plugs and wires (most commonly the issue)

• Loose or disconnected hoses on and around the engine (not the coolant hoses that go to and from the radiator) are frequently culprits behind intermittent engine operation.

• Loose connections at the positive and negative battery terminals

• Very dirty or clogged air filters can also cause your engine to underperform.

• Loose timing belts are another likely cause. A mechanic will check these and replace them if they appear loose and worn. To check for engine-mount problems, the mechanic may try shifting from "neutral" to "drive" and back, while the engine is running. If the vibrations disappear or reduce dramatically in "neutral," it’s likely that you need new engine mounts.