Rough idle

1997 FORD EXCURSION
300,000 MILES • 5.4L • V8 • 4WD • AUTOMATIC
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ROBERT RIFFE
  • MEMBER
  • 40 POSTS
Replaced coils and plugs. Deleted the EGR and have ran 4 plus full tanks. What is causing the rough idle? Running out of ideas. Cleaned throttle body, looked at MAF. Looked good. Throttle position sensor?
Apr 7, 2020 at 10:12 AM
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ASEMASTER6371
  • ✓ASE Certified Mechanic
  • 52,796 POSTS
  • ASE Certified Mechanic
Good afternoon,

Are there any codes set?

I would start with a compression test to be sure there is no cylinder damage.

https://www.2carpros.com/articles/how-to-test-engine-compression

You have covered the basics so we need to move further into checks.

https://www.2carpros.com/articles/engine-surges

Roy
Apr 7, 2020 at 11:06 AM
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BMDOUBLE
  • ✓ASE Certified Mechanic
  • 1,139 POSTS
  • ASE Certified Mechanic
I'm on the same page with Roy! Start with a compression test to make the base engine is in good shape. On semi-rare occasions the roller follower will fall off or a valve spring will break on a particular cylinder and have you chasing your tail for quite a while! That's where the codes will come in handy to identify a possible cylinder, then go from there.
Apr 7, 2020 at 11:20 AM
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