215k miles, 93 245

I've looked for air intake hose leaks, replaced the O2 sensor and fuel pressure regulator, and checked the fuses. I've cleaned the throttle body and idle air valve with cleaner and tightened all the hoses.

The engine sputters a bit when first accelerating from a stop, then drives fine. After about 4 or 5 days of this, the Check Engine Light (CEL) comes on. Picked up two codes related to Excessive lean/rich mixture at idle and cruise. I'm thinking the intake manifold gasket is the problem?

After disconnecting the battery (to reset the computer), the CEL stays off for 4 or 5 days and comes right back in. Once the CEL comes in, the symptom disappears. I could drive the car fine indefinately with the CEL illuminated (because the sputtering goes away), but I don't like having the CEL on.

I've posted this problem a couple of times before and received all the suggestions that I listed in the first sentence, but nothing has helped. I'm about ready to take her in to the repair shop to find the root cause..but I just wanted to pulse the brickboard again to see if anyone can help.

Thanks,
Cabbie

Perhaps holes in exhaust downpipe around the lower bend near bracket
Before the cat convertor. Causes the codes you mention.

Check the A/C. If it is low, it can cycle and cause the issue you describe.

TomM

If it does this when cold, you ought to be able to (on a cold motor for safetys sake) spray at the intake/head joint with a can of starting fluid(either) and if there is a leak get a rise out of the idle or some such. Be safe, etc, etc.
If all is tight you can drown the exterior of the motor and air hoses and get no change in idle. Again, cold motor, for safetys sake. I have known these intake gaskets to leak, and the intake bolts to be loose over time. It isn't too hard a job to change them out, be aware of other stuff that has to be moved that might break in the process.