Why when the temperature is above 65 degrees outside my engine surges

  • 1996 FORD PROBE
  • 100,000 MILES
When stopped at 1000 rpm and in park at 1200 to 1500 rpm?

It runs a little above normal but not too hot during this time also. I do hear the fan kick in when the temperature starts going above normal.

At night or evening it runs fine. The engine temperature is steady and the rpm stays around 665 rpm.

The vacuum and compression are OK. It has new plugs and gas filter (4 months old), oil changed (1 month ago). No bubbles in coolant, oil looks normal.

I have been experiencing some coolant loss adding about a quart every 2 to 3 weeks but haven't noticed any leaks.

The upper and lower radiator hoses are hot. I replaced the radiator cap but still experienced the problem. I have a small crack in the filler cap (has no plunger) but I've never noticed coolant leak from it. I have to special order a filler cap.

NOTE: The problem was nonexistent during the fall and winter months.

Do you
have the same problem?
Friday, June 1st, 2012 AT 1:24 PM

1 Reply

Check the ECT, it provides signals to the PCM to control the cooling fans and it could be providing the wrong reading which would indicate to the PCM that the idling speed needs to be increased as the coolant temperature is below operating temperature.
Was this
Friday, June 1st, 2012 AT 2:06 PM

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