Why does car engine surges in weather above 70 degrees F.

Tiny
LRYMCD
  • 1996 FORD PROBE
  • 100,000 MILES

My engine surges when the outside temperatures are above 70 degrees, 100- rpms when stopped, 1200 to 1500 rpm when in park.

Someone from 2carpros suggested checking my ECT.

When the outside temperature is above 70 degrees F my engine surges at 1000 rpm when stopped and 1200 to 1500 rpm when in park. I have no problems at night, during the fall and winter or when temperatures are below 70.

An Expert on this site suggested checking my ECT.

OK. I checked the ECT with a ohm meter. I used a chart online as a reference. This is what I read:

68 degrees F - I read 2.3 k ohms, the chart read 37.30, my ford manual states 2200 (2.2) to 2700 (2.7). Is the Ford manual accurate?

104 degrees - I read 1.14 k ohms, the chart read 16.15

122 degrees F - I read.60 K ohms, the chart read 10.97.

140 degrees F - I read.50 k ohms, the chart read 7.70

I've not tested it at engine temperature (180 degrees F) but the ford manual states 290 (.29) to 350 (.35). I don't know if this is accurate.

Please advise.

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Sunday, June 3rd, 2012 AT 1:45 PM

4 Replies

Tiny
ASEMASTER6371
  • EXPERT
  • 25,554 POSTS

You need to use the last column for reference, not the voltage chart. You are measuring the ohms, not volts.

Also. Check the fuel pressure if this checks out.

Roy

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Sunday, June 3rd, 2012 AT 1:55 PM
Tiny
LRYMCD
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Yes. I did use the last column.

Example: 104 degrees - I read 1.14 k ohms, the chart read 16.15. "I read" means this is ohm reading from my ECT. It this correct?

I have a new fuel pressure regulator (3 months old). I'll have to read how to measure fuel pressure.

What is the diagnosis?

Thanks

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Sunday, June 3rd, 2012 AT 2:49 PM
Tiny
ASEMASTER6371
  • EXPERT
  • 25,554 POSTS

You need a pressure gauge to read the pressure, you can rent one from a parts store and check as needed. Look for 40 lbs.

Roy

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Sunday, June 3rd, 2012 AT 2:52 PM
Tiny
LRYMCD
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OK. I'll check the fuel pressure. How are my ohm readings from the previous message?

Thanks

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Sunday, June 3rd, 2012 AT 9:23 PM

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