Engine dies out on start up

Tiny
SHANEMJEFFERS
  • MEMBER
  • 1998 FORD EXPEDITION
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 220,000 MILES
Hey folks. I have a 1998 Ford Expedition, upon turning the key the engine fires over but immediately dies out. I have replaced the IAC valve to no avail. I have tried spraying gasoline in the throttle body and sure enough it idles. But heres the kicker. When I have the IAC plugged in it immediately dies out, however when I unplug it it will idle for a few minutes (rough) before it dies out. Please help
Tuesday, August 12th, 2014 AT 6:34 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
Have you checked fuel pump pressure? Also, has the check engine light come on?
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Tuesday, August 12th, 2014 AT 10:10 PM
Tiny
SHANEMJEFFERS
  • MEMBER
  • 7 POSTS
Fuel pressure was good, and yes the check engine light was on. I did finally get it figured out though, It was a vacuum line on the air intake causing the engine to stall. It showed all the symptoms of the IAC sensor but was as simple as a broken line. Thank you for the response though!
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Tuesday, August 12th, 2014 AT 10:38 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,170 POSTS
Glad you found it. On this engine, there are a couple behind the throttle body that have 90 degree bends in them. If there is a vacuum leak, usually it is one of them.
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Wednesday, August 13th, 2014 AT 4:08 PM

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