1997 Buick randomly runs rough during rain and will not start the next day

About 2 weeks ago my 1997 Buick Park Ave (115,000 miles) began running bad during a heavy rain storm. It was running fine. Then all of a sudden at a stop light the motor hesitated and wanted to stall. I nursed the gas peddle and limped home and turned the car off. The car hesitated and sputtered all the way home as if I was running out of gas.The next day the car would not start. It turned over but would not start. I tried starting the car for three days. My mechanic friend later diagnosed the car and stated the computer was not functioning correctly. He replaced the computer. The new computer seemed to correct the problem. The car ran great for the next 2 weeks. Yesterday, it was raining hard while I drove the car about 150 miles without any problem. Then suddenly again the motor started running badly. Again, the motor wanted to stall and hesitate as if I was running out of gas. I limped home again. This morning I tried to start the car without any luck. In addition to installing a new computer, In the last 2 months I have changed all the fuel injectors and installed new spark plugs.I have also changed the fuel pump and repaired the fuel tank. My mechanic say the cam sensor and crank sensor are operating correctly. There is spark coming from the coil packs and to the spark plugs. Can you offer some suggestions so I do not have to randomly change parts.

A mechanic needs to perform this diagnosis while the car is a no-start. Facts need to be gathered such as does the engine light go off during cranking, measuring the fuel pressure during cranking, checking for spark on all six cylinders, verifying RPM on scan tool data, and verifying injector pulse with noid light tester.

Water can negatively affect sensors, ignition module, coil, plug wires, relays, wire connectors and power supply and ground to critical components.

Those of us that have worked on these cars for years know that there is no pattern failure for a cranks with no start. We have all seen diagnostically difficult end results like bad grounds in the trunk, bad grounds in the right kick panel, bad relays, burned maxifuse terminals, bad ignition switches, bad main ground on transmission bracket, bad battery cable connections and more.

Many of these cars go to the scrap yard for cascade electronics failure that never get diagnosed.

The last one of these cars that I personally diagnosed for a similar complaint turned out to be a problem at the battery connection. The two positive cables were corroded and one was isolated from the battery. The previous one was a bad ground to the fuel pump.

Professional diagnosis is my recommendation because you are correct that guessing will continue to provide no results.

Usually it’s plug wires or coil when moist air allows the spark jumps to ground. You could spray the engine with a squirt bottle in the dark and look for the arching spark. At least mabe isolate where the moisture is causing the short.

Usually this symptom is in the high voltage circuit. On older cars it would often be a cracked coil. But your car’s coil is probably hidden from view so you’d need a mechanic to check that. But if it has visible spark plug wires – on the 97 this is likely – look at them carefully under good light. Twist them a bit, under a magnifier if necessary, see if there is any signs of cracks in the spark plug wire insulation.

I had a problem like this w/ a late 70’s VW Rabbit, and in an attempt to diagnose it I’d spray the entire engine area with a fine mist of water and it wouldn’t even sputter. No matter where I sprayed the water, it didn’t phase the engine a bit. But if I drove over a pothole filled with water at over 35 mph, the engine would consistently die on the spot. It would restart in 30 to 60 minutes and run fine. Eventually I got desperate enough I removed the coil from the firewall and placed it on my workbench and cleaned it thoroughly. Voila, a tiny, almost microscopic crack in the ceramic. Replaced the coil and never experienced that problem again.