Mechanical question about my car, 1997 Cadillac Deville.
I have had trouble with it for over a year. It misfires at idle. It has given numerous codes. Always P0300, meaning random misfires. At the moment P1139 and P1153. Those are for two different oxygen sensors. However, I have replaced three oxygen sensors and still getting codes, and still misfiring.
Recently I noticed the lights on my headlight switch flickering, and lights in the door panels too. It is not consistent, but is randomly happening.
So, I am wondering if there is a problem in my light switch causing a problem getting electricity to the oxygen sensors.
Maybe it has an electrical short somewhere else even?
I really like this car. 124,000 miles on it, and runs like a champ except right after FIRST starting it.
What makes this problem better or worse?
Idle runs roughly
How long has your 1997 Cadillac DeVille had this problem?
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Hello. The flickering / surging lights are likely caused by the charging system and battery. Have your battery checked to ensure it is good, fully charged and able to handle a sustained load. Have your charging system checked to ensure the alternator puts out enough amps and sustains the proper reference voltage. This, however, has nothing to do with your check engine light and your codes. If your idle should fluctuate, your electrical system can also surge as a result, meaning an engine performance problem is presiding over a charging system concern.
You do not, however, have a "short" based on what you've shared.
The P0300 - random misfire. Have you checked engine compression? Have you checked your ignition system? The 4 coils - have they been checked for proper performance? Is your fuel system delivering as it should?
Bank one sensor two and bank two sensor one -- odd combination of diagnostic trouble codes for heated oxygen sensor performance. Have you utilized a diagnostic tool to investigate what the readings are of all 4 sensors?
Replacing the sensors is a guess, and I'm not surprised it hasn't fixed anything. Troubleshooting following the shop manual, checking wiring harnesses as directed, and monitoring performance with a diagnostic tool is essential. Good luck.
