I have a 1997 Sable with the 3.0l Vulcan which now has 101k miles. I bought it used with 98k.

Occasionally, when I start the car, the motor feels like it is shaking and sounds like it is about to stall but never does. When I hear this event, I press the accelerator for a second or two, and the event disappears. I have had this problem since I bought the car.

I have replaced the spark plugs with Motorcraft Platinum, the spark plug wires, the ignition coil, the IAC, the Alternator, the Battery, the Fuel Filter, the PCV Valve, and used Dry Gas and Techron Fuel System Cleaner but can never seem to eliminate this occasional problem. I even changed the Fuel Pump Fuse. My mechanic replaced the CAM Position Sensor.

The car runs very smoothly after starting, and accelerates without hesitation or misfire. I have changed all the fluids, and have no leaks. Moreover, the car has been reliable and comfortable to drive.

A friend of mine suggested it is bad gas. I admit, I did fill up at a Delta gas station a few times. Since then, I have been filling up with BP, Shell or Exxon Regular 87 Octane.

I even tried two bottles of Gumout Octane Booster which seemed to smooth out the starting issue but am not sure.

I was wondering whether the new spark plugs I installed, or the fact that the car now has 101k miles has now increased the need for higher octane.

Like I said, this problem is intermittent.

Anyone have any ideas? Thanks

 

Have you noticed any difference in the appearance of the old plugs that you changed?
Just wondering if coolant or extra fuel is leaking into one of the cyls when it sets. It doesn't have to be a lot just enough to mess up the mixture when first starting.

 

Not really. They just look worn.

I am going to try and spray clean the Throttle Body. Some articles that I read on the web suggest that may be the TPS is on the verge of going bad, and should be replaced which might be the cause of my intermittent problem.