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At roughly 162,000 miles. Regal is a '92. Check engine light sometimes comes on when I leave my house to go to the store but will go off for the trip home. Just did an oil and filter and changed the fuel filter in the last one or two hundred miles. This has only started within the last few days. What could some of the problems be? This is the first time this light has come on since I've owned the car. Last major tuneup was about 10,000 miles ago where I did an oil and filter, changed PVC valve, replaced air filter, and replaced the spark plugs and spark plug cables. All fluids have been kept topped up.

some times it can be a little vacuum leak.

Firstly, my congrats on owning the original (now double great great grandfather V6. Probably the best ancestor V6 that GM has ever produced. Nearly all (surely most) V6's now produced made are kin of of your engine. Many were aluminum headed but some of the earliest were all cast iron which by all practical means, one could consider the old 3800 blocks as virtually invincible.

Now that the sunshine is on your engine I will give you the good news. If the light is going on and off you will most likely find that the OBD1 code will involve your Oxygen Sensor. If you had every cubic foot of exhaust gas for 20 years and 162,000 miles going past you, chances are that you would be giving someone the signal to 'retire me'.

Sir, you need a new O2 sensor. My decision is based upon inheritance of the specified mean time before failure of the part along with speculated hours of in service time in conjunction with the symptoms given.

In other words, your O2 sensor has done it's time and shows symptoms that warrant replacement.. More specifically, It takes a little bit longer for an old tired O2 sensor to warm up, longer than the amount of time that the ECU is pre-programmed to give it before it should expect to start seeing a workable signal. this is why the light goes off after a bit. You might notice that it is usually after you engine has been running for a while does the light turn off. This can be verified by the actual OBD code that is up and reported to the memory in the ECU. Probably code 1 3 or 4 3 or 4 4.

In any case, have that O2 sensor replaced (about $40) and that's it, you're done and ready for another 162K

Could be a defective seal on the gas cap to tank or a vacuum leak in one of the evap canister vacuum lines to the charcoal canister.