Park Avenue Problems

Just looked at a customer's vehicle that is having problems starting. Checked engine codes and came up with P131 P171 P305. So we've got a bank 1 O2 sensor fault, bank 1 lean fault and misfire on cyl 5. He says the car runs poorly (better when cold) idles poorly and when he shuts the car off has a difficult time getting it started again. I did witness this at my shop. Seemed to not have enough fuel or something. After about 30 minutes of waiting it fired right up but ran poorly. He's taken it to a half dozen mechanics and has had what amounts to a $1,200 tune up done. New plugs, wires, coil packs, and O2 sensors. Here's my thought. Leaky intake gasket (likely the worst around cyl 5) is causing too much air to enter the left bank causing it to run lean and causing a misfire on cyl 5. O2 sensor fault is a result of engine running lean and not source of the problem. Not sure why it doesn't start though. Said it seems to start fine when the engine is cold but when it has been run for a while and then is shut down it doesn't want to start up again. Maybe the warm air being less dense has an easier time getting through the bad intake gasket?? Not sure. A short disclaimer. I am a body shop and don't know why I got involved but I am because he's been a good customer. Anything I'm overlooking or do you think I'm on the right track. Thanks for the help fellas.

Scott

If the intake gasket indeed has a leak, it may leak less or more depending on the temperature. Have you checked plug #5 and compared it's condition to the other plugs?

What is the year and mileage on this car?

The car is a '96 with about 180K miles on it's non-supercharged 3.8. I have done nothing to the car other than pulling the codes and talking to the owner. He lives about 45 minutes out of town and couldn't leave the vehicle today so I'm assuming he'll drop it off on Monday. I called him and told him to spray a little ether around the intake manifold and the vacuum lines to see if he could find any proof of a leak and have not yet heard from him. As for the plugs I have not pulled them. If there is a big enough leak in the intake gasket to cause the misfire code I'm assuming the plug will be either wet or possibly burnt?? Something else I was thinking was a bad head gasket or warped head essentially doing the same thing... allowing too much air into the cyl. Can anyone tell me where the sensor is that trips the P0171 lean code? If it's in the intake manifold then I would think that would eliminate the head/head gasket theory.

Are you working in a repair shop? Anyway the 171 is the o2 sensor itself reporting to the pcm. This can be part of the misfire code as the o2 stream contains too much o2 as a result of the cylinder not firing..