2006 Liberty 4x4 with 3.7L - Scheduled Maintenance Is Critical

ron.dittmer

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We own a 2006 Liberty Sport 4x4 with the 3.7L gas engine, now with 87,000 miles. We bought it used in 2009 with 29,000 miles. I have been real good with maintaining the vehicle.....or so I thought.

One thing that surprised me about the 3.7L engine is the scheduled frequency the spark plugs need to be changed. I assumed they were 100,000 mile plugs like my other two 2006 & 2007 model year vehicles. Our Liberty started developing engine hesitation at around 60,000 miles. I eventually decided to replace the spark plugs at 75,000 miles installing the exact same spec'd plugs, and the engine immediately reverted back to good normal operation. The center electrode in the spark plugs was worn below the ceramic insulator.

I also had some automatic transmission behavioral quirkiness developing. About 10,000 miles after changing the spark plugs, I replaced the transmission fluid & filter and that quirkiness went away.

I recently performed a serious parking brake rebuild here, posted with many detailed step-by-step pictures. https://www.jeepkj.com/threads/2006-liberty-sport-4x4-total-parking-brake-rebuild-for-68.77044/ The project required draining the rear differential, so now I have that fluid changed. The only original fluid today is in the transfer case.

So I learned that scheduled maintenance is critical on a 2006 Liberty 4x4 with 3.7L engine.

BTW: For those interested, filling the rear differential with new gear oil was easy using this affordable suction gun from Harbor Freight. https://www.harborfreight.com/oil-suction-gun-95468.html A bottle of gear oil takes only two draws to empty. The gun holds 17 ounces. It is the exact same size as a standard grease gun.
 

LibertyTC

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Yes good to do maintenance on our precious Jeeps. Rule #1 always refer to your owners manual for fluid type & specifications. Also mentions towing rear diff specs +
Spark plugs I replace at every 35 -40 k miles. The Jeep coil packs fires the NGK ZFR6F-11G hot & burns though the gaps easily.
Transmission fluid & filter, I do every 60 k miles. Or anytime you may get a trans temp light. ( ATF+4 fluid overheated)
 

LibertyTC

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Jeep coil packs do fire plugs very well. Jeep Spec is for copper core plugs. It has a larger center electrode and provides a solid spark.
Those that have tried platinum or Iridium find that the Jeep will not run as well, compared to the NGK ZFR6F-11G
 

mercdudecbr600

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Well I've been running NGK iridiums for the last few years. No issues, good mileage, power, idle, with very little wear on the plugs. I guess YMMV
 

KJ_Liverpool

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Yes good to do maintenance on our precious Jeeps. Rule #1 always refer to your owners manual for fluid type & specifications. Also mentions towing rear diff specs +
Spark plugs I replace at every 35 -40 k miles. The Jeep coil packs fires the NGK ZFR6F-11G hot & burns though the gaps easily.
Transmission fluid & filter, I do every 60 k miles. Or anytime you may get a trans temp light. ( ATF+4 fluid overheated)
I have an after-market transmission pan with a drain plug and I change the transmission fluid at every oil change, which is every six months. Every six changes I drop the pan and put a new filter on.
 

tommudd

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Well I've been running NGK iridiums for the last few years. No issues, good mileage, power, idle, with very little wear on the plugs. I guess YMMV
And i have pulled several plugs out due to stupid repair shops/ autozones etc talking people in to iridiums and plats
misfire . etc
NGK coppers fixed all the issues, I keep 5-6 sets at the shop at all times just for that reason
You gain nothing at all with anything but copper NGKs
 
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tommudd

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And back on track, maintenance is very important on any type of vehicle
Even my skid steer, tractors , all the various vehicles I have owned since 1970 !
One reason I have always had people waiting/wanting to buy mine, due to them knowing all maintenance was always done sooner , not later or never
 

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