1999 GMC Sierra Spark plug covers

Tiny
GWATS1957
  • MEMBER
  • 1999 GMC SIERRA
  • V8
  • 2WD
  • AUTOMATIC
  • 179,000 MILES
Each of my spark plugs has a metal sleeve over the plug wire near the engine block. What is this for?
Sunday, March 7th, 2010 AT 8:05 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,742 POSTS
They reduce radio frequency interference (RFI) from interfering with the multitude of computers. The magnetically-induced voltages can be greater than some of the tiny signal voltages coming from the sensors and the computers will think the various spikes are sensor problems.

Caradiodoc
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Sunday, March 7th, 2010 AT 11:35 AM

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