Rough Idle...code P2128
I have a 2004 Buick Rainier with the 4.2L I6 2wd. It has a 135,000 miles and I recently changed out the spark plugs and while doing so, I noticed some oil on the a few of the plugs. I did some research and decided to changed the valve cover gasket. My dad and I purchased a manual for the engine and was able to change out the gasket after many hours. We also changed the intake gaskets since it was torn apart. The repair went back together with out a problem and all the connectors, hoses, everything was reconnected. The car started up and would idle rough for a few minutes then die. It also two engine lights showing on the dashboard. Did some research and decided to do a manual reset of the computer. Held both disconnected battery cables together for 30 seconds then reconnected. Car started fine and ran fine. Drove it probably 70 miles after I did this and had no problems. The car sat overnight, and in the morning would start, idle rough, then die. Also, one engine light came on in the dashboard. Finally got the car to run and it eventually smoothed out and ran fine. Took the car into the local mechanic to have the code ran and he couldn't get to it that day. It sat there overnight and the next day when I called him he said the car started and ran fine. He ran the code and it came back as a Cam Phaser code. He did not give me the actual code and I could get that code probably Monday. Anyway, I had him just reset the code and he drove the car to my house. The car sat for 7 days and when I finally drove it again it started right up and ran perfectly. Drove it 40 miles and had no problems. Came home, shut the car off, drove it again later in the evening, no problems. The car sat overnight and this morning, when out to drive it and it started, rough idled then died. An engine light also came on again. I needed to drive it so I did another manual reset of the computer and it started and runs fine now. Went to drive again after the car sat overnight and same thing happened. Started, idled rough then died. Two lights came on in the dashboard. One was a check engine light other was the lower power light. Ran the codes at O'reillys and it was P2128..
Car starts and idles fine today but stays in the low power mode.
I do not know what the problem is. Electrical/Computer? Mechanical? Any help would be greatly appreciated.