Driving home last week the engine started running rough and the CEL came on, blinking. checked the codes, and determined i needed to replace the #6 coil pack. I've replaced the coil, and cleared the codes. Now the engine runs fine until it hits 3100rpm, then it it drops back to about 2600rpm and starts surging rapidly between 2600 and 3100 rpm. Then the CEL comes back on. Checked the codes again, and get the same two codes. Any body got any ideas what to check next?

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2002 Jeep Liberty Sport with Trak-Loc
3" lift: OME struts, springs and shocks; Jeepin by Al UCAs and strut spacers
Full skids by Rusty's Offroad and Mopar
245/75/R16 Dunlop A/Ts on Procomp Soft 8s
A few lights and performance mods.

http://www.alphaomegaoffroad.com

Did you check the plugs when you changed the coil?

No, I just had the plugs replaced recently.

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2002 Jeep Liberty Sport with Trak-Loc
3" lift: OME struts, springs and shocks; Jeepin by Al UCAs and strut spacers
Full skids by Rusty's Offroad and Mopar
245/75/R16 Dunlop A/Ts on Procomp Soft 8s
A few lights and performance mods.

http://www.alphaomegaoffroad.com

OK... I replaced all the plugs, cleared the code, and took it for a test drive. Its still running rough, and now just throws code P0356. Any ideas anyone?

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2002 Jeep Liberty Sport with Trak-Loc
3" lift: OME struts, springs and shocks; Jeepin by Al UCAs and strut spacers
Full skids by Rusty's Offroad and Mopar
245/75/R16 Dunlop A/Ts on Procomp Soft 8s
A few lights and performance mods.

http://www.alphaomegaoffroad.com