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Questions and Answers

Which Spark Plug For A Jeep TJ?

Q. I have a 1999 Jeep TJ with the 4.0 liter 6 cylinder 5 speed. On the emission sticker under the hood it tells me to use Champion RC12ECC plugs gaped at 0.89 mm but after I installed them the Jeep ran a little rough at idle. The previous plugs were installed were RC12LYC and the jeep idled great. What do I do? Reinstall some new RC12LYC or keep the one's Jeep wants me to use?


Which Spark Plug For A Jeep TJ?

A. There was a recall in December 1998 concerning the spark plugs. The RC12LYC were the incorrect plug for that vehicle.

No. 8062
December 1998

Emissions Recalls # 8061 and # 8062 - Spark Plugs

Certain 1999 Model Year Jeep Cherokee (XJ) and Wrangler (TJ) Vehicles Equipped With a 2.5 liter or 4.0 liter Engine, Built Through August 12, 1998 (MDH 0812XX) and Equipped With a:

  • Federal Emission Control System - Recall #8061
  • California Emission Control System - Recall #8062

The spark plugs of the above listed vehicles may fail. This will cause the engine to misfire and illuminate the Check Engine light. To correct this condition, all spark plugs must be replaced on the affected vehicles.

The correct plug is, Chrysler P/N 56O41402AB or Champion RC12ECC gapped at 0.035" or 0.89 mm.

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© 2003 Vincent T. Ciulla

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