I have a 2009 Kia Borrego, 3.8 V6, VIN KNDJH741295037401 with 86,000 miles. I started getting a P0018 code about a year ago. The vehicle ran rough on occasion. the first month. Since then, it ran fine for about a year (10,000 miles at most) with CEL on. A few weeks ago, it acted up again and it threw additional misfire codes and then back to normal for a few weeks. The local Kia wanted to replace chains, tensioners, guides, OCV's, and 4 CVVT's (intake and exhaust) for a lot of $$$. Having worked on a few engines, I decided to tear it down myself. It seems that the driver side tensioner failed. The old chain was also hitting the cover and caused a small gouge. CVVTs show some minor wear on the face of the teeth but could not find exact replacements and decided to reuse. I check the diameter with a mic and they seem to be OK. Installed aftermarket chains, guides, tensioners, crank sprockets. After getting all the cams and crank to TDC, and setting the colored chain links on the "indicator dots" on the gears and sprockets, I rotated clockwise a couple turns. As I turned, the tensioners moved in and out a bit and when the cams on the slack side sprung past the "tipping point" they would snap clockwise causing the tensioner to instantly compress and push the chain towards the tension CVVT. It seems that the millisecond that the cam on the tension side feels the slack chain, one of the tension CVVTs would slip a few teeth. When I get the thing all set to turn, the engine does not seem to turn smooth as I envisioned (with plugs out). I have retimed the engine to the point I can now do it blindfolded trying to figure out the problem. The old chains seem to be the same as the new (#links, width) but one can tell that they have stretched a bit. I purchased the parts from aftermarket EBAY but the vendor had an excellent (and many) feedback. There have been some revisions to this engine so, I am considering another set of new-old-stock chains to try. Would no plugs are in and no oil pressure be part of the cause of my dilemma? Am I missing something? Any help would be appreciated.