1996 Mercury Sable Possible IAC Hiccup?

Tiny
OBERON567
  • MEMBER
  • 1996 MERCURY SABLE
Engine Performance problem
1996 Mercury Sable 6 cyl Automatic 100, 00 miles

Problem has been persisting for a few months. When I drive highway speeds, and then get off the highway or stop at a toll and my RPMs drop, as soon as I accelerate my check engine comes on, blinking for a few minutes, and then turns solid. When blinking my engine idles rough. Engine codes say misfire on Cylinders 1 & 3. Have gotten a tune up and replaced coil, to no avail. The Ford dealership could not figure out what was wrong in their initial diagnostic and wanted an additional fee for further testing.

Since the cold weather has started, it is worse. The light still comes on under the same conditions, but now when I start my car it right away idles at around 1200 RPM, and doesn't feel/sound happy. Once it warms up a bit it idles closer to 750, but it takes a while to get there, and even just accelerating after a red light can see the RPM jump to 2300 - 2500.

I am thinking it might be the IAC. If I unplug the IAC while the engine is running the car does not stall. But I do not know for sure, and have spent enough at this point to be dissuaded from buying something as a means of a test.

Does it sound like the IAC is the culprit? Are there any other tests I could do to confirm this, or anything else I should be checking?
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Friday, December 18th, 2009 AT 1:53 PM

4 Replies

Tiny
RASMATAZ
  • MEMBER
Hi oberon56, Welcome to 2carpros and TY for the donation and selecting us as your auto repair site Feel free to ask questions at anytime and Merry Christmas and a Happy New Year 2010

Clean and test the IACV and also the EGR valve, and test the TPS and MAF sensors

Engine misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Friday, December 18th, 2009 AT 4:55 PM
Tiny
BMRFIXIT
  • EXPERT
If its stalling, low idle, high idle, no or hard start
I would suspect an IAC valve
but a misfire codes that is NOT an IAC
if had a tune up and coil was checked and replaced
next step should be injectors and compression test
weak valve spring also may do it
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Friday, December 18th, 2009 AT 5:00 PM
Tiny
OBERON567
  • MEMBER
I know how to clean the IAC valve.

*How do I clean the EGR Valve?

*How do I test the IAC and EGR valves? Unplugging the IAC while the engine is idling does NOT cause it to stall. Unplugging the EGR Valve while the engine is idling DOES cause it to stall. Are there additional ways to test these?

*How do I test the TPS and MAF sensors?

*Also, don't the TPS and MAF sensors have their own Engine Light codes if they fail? (Or would they cause the more generic misfire code if they were causing a lean mix?)

Thanks!
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Friday, December 18th, 2009 AT 11:16 PM
Tiny
RASMATAZ
  • MEMBER
*Also, don't the TPS and MAF sensors have their own Engine Light codes if they fail? (Or would they cause the more generic misfire code if they were causing a lean mix?) Sometimes problems exist on these sensors that will not trigger the CEL.

Have you clean out the idle air control valve and its passages? You need a repair manual. About the EGR valve it will cause the engine to misfire due to it leaning effects on the fuel and air mix ratio due to carbon causing it to cracked open
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Saturday, December 19th, 2009 AT 12:04 AM

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