Hello,


My 2001 Sable has the check engine light on. First, the car started rough idle. Then the light. Had a P0301 code. Cylinder 1 misfire. Replaced. Old plug looked as if it had been extra hot. Cleared codes. Light back on. Now, have cylinder 1 code (301) and too lean codes (171, 174) in both banks. If I start the car for a few minutes. Wait a few minutes and start again, the engine gets smoother. Parts shop suggested O2 sensors. I know there are 2 up-stream and 2 down-stream. Is the down-stream sensors the best place to start?
Thanks for any help.

 

Try to start with the simple things first.
Something that can affect both banks and is easier to check is the PCV hose and elbow. Common problem, and pretty easy to check . Both pieces seem to develop a crack or opening and can result in a lean condition. There are other possible causes like MAP sensor or intake gaskets. The MAP sensor could be sending invalid info to the computer and sometimes cleaning the sensor with a spray specific for MAP sensors will help. Try the simple things first.
From what you described with the #1 plug, how long have the plugs been in there , which engine , & what kind of mileage is on the engine?

 

I like simple. The engine is 3.0L DOHC V6 Duratec. I have 168,000 miles. I changed the wires and plugs probably 2 years ago. The car sat for several months while I ran down a fuel pump problem.
I replaced the PCV about a year ago. I checked the hose and elbow today. The elbow had been replaced several years ago. The old one was collapsing.
I will do the MAP sensor cleaning spray.
Thank you for the info.

 

I got the CRC MAP sensor cleaner. Took the sensor out. Cleaned it. Car starts smoother. Real test is after it cools overnight. Will replace the air filter. I may have a vacuum leak. Unknown sound. Will keep checking.
Car is always smoother after it warms up.

 

Replaced the air filter. Started the car. Still a little rough, but better. Removed the air intake system again. Found what could have been a vacuum leak. Replaced rubber pieces and added a clamp. Smoother. Still died after driving a mile down the road. I was letting it idle. The lights dimmed and the car died. Started right up. Tomorrow will be cold here. See how that test goes.

 

Still have the same basic problem. Found during a different search, another person with the same description of problems. That person finally resolved it with lower intake manifold gaskets. I have had that manifold off many times. Replacement kit has both upper and lower rubber gaskets. Less than $20.00. Thinking about it. May do it this weekend.

 

Replaced the upper and lower manifold gaskets. Added a clamp to the hose at the pcv. Could not get to the store or would have replaced it. Hose was not cracked, but the fit was looser than I would like. Back together and running smooth.