I just recently purchased a 1990 LS 400. The engine runs fine when it is cold, but once it heats up, the check engine light comes on and the car starts sputtering and even dies at times. This car sat for a couple of years so I had the routine stuff done such as a tune-up, new fuel filter and injector cleaning. Before I have to take it to the dealership, I wanted to pick your brains for a possible solution. All coments are appreciated... thanks.

 

Sounds like a oxygen sensor.

 

Since my car is pre-OB ii, is there a way I can determine which one is malfunctioning?

 

When you get the check engine light, drive over to Autozone and have them scan your codes for free. (not every place has the scanning tool though for pre 96 cars.)

 

When you first start the car, it runs an open loop set-up, basically manually enriching the fuel mixture for a smooth running warm-up period. Once the car is warm, it begins taking the signals from the 02's to adjust the fuel mix. This is definately an O2, and like stated above, Autozone can tell you which one.
Brandon

 

I appreciate your help!