Originally Posted by orbit398

Problem Solved
Figured I'd let others know what the problem was. Engine running lean and throwing the P0171 & P0174 codes due to small air leak. Only at idle would this symptoms appear. Ran great other wise. Searched and searched for leak using starter fluid on vacuum lines - found nothing. MAF sensor replacement didn't affect it. This rough engine at idle started soon after the oil change. Never put the two together.

On the oil cap is two triangles that one is to line up, I assume to indicate the cap is sufficiently tight. Well that was the issue. The triangles were lined up perfect. Problem was is the seal under the cap wasn't fulling mating with the surface (all the time) and was the source of the small air leak. The engine pulls a vacuum and was getting a little air from the oil cap. Had I tighten it like normal and not lined the triangles up, I would have never had then lean codes/engine running rough.

Local shop pressurized the engine via the intake with smoke of some sort and saw it coming out of the oil cap area. A new oil cap solved the problem. go figure.....

Originally Posted by pizzaguy

I noticed a long time ago that these engines will idle just fine UNTIL you remove the oil cap - then they sputter and surge. It is OBVIOUS that the oil cap is sealing well when you see THAT.

If your idle speed varies and does NOT get worse when you remove the cap, you probably have a cap that is not sealing well OR you have a massive vacuum leak elsewhere.

Originally Posted by kowaltoboggan

Thanks, guys. I removed the engine cover and refit it. This morning, the check engine light didn't come on. However, it went on on the way home from work even though it ran well. That is my fourth time driving it and I still haven't gotten used to the car to know what is normal. Will need a few weekends to figure it out. Also, since we moved and haven't received our stuff yet, I have none of my tools with me to help me diagnose.

All that said, am thrilled with the car and will get it into tip top shape.

From this list, I gathered it will be good to replace the cam and crank position sensors so have ordered those, but realize they may not be related to this P0170 and P0174 issue. Will need to chase a potential air leak before I look at replacing the MAF. However it turns out, am confident knowing you all are here on the forum. Thanks again.

John