1992 Geo Prizm Engine won't shut off

Tiny
JK35CHEV
  • MEMBER
  • 1992 GEO PRIZM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 53,000 MILES
My mother in law's Geo Prism is not driven much. Only about 10 miles a week and lately when she starts it, it pings and won't shut off. It has been kept up mechanically, but I am afraid some parts are getting sticky or plugged from a history of slow speed driving (no more than 45 MPH) and low mileage on a regular basis. What could be the problem?
Tuesday, October 27th, 2009 AT 8:10 PM

1 Reply

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
If is dieseling or sometimes called "run on" where you turn key off and engine chugs, not firing on all cylinders, but not shutting off, the problem is excessive carbon build up in head and pistons causing carbon hot spots.

This is abnormal for a FI car, since fuel supply is also shut off, so in addition to above, you may have leaking injectors.

I would start by running a couple of cans of SeaFoam in tank. It will help cleaning carbon from engine.
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Wednesday, October 28th, 2009 AT 8:34 AM

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