[Manarius]

Originally Posted by dgzieg

Hi, long time lurker, first time poster. My '94 LSI started intermittently idling rough a couple of months ago. Seemed like the hotter the weather, the more likely I'd experience a rough idle. Since it was intermittent it was difficult to make a correlation. Anyway, finally started to get CEL indication. After a couple of weeks of the CEL lighting briefly (not even every day), I pulled the codes. I got 37 (Oxygen sensor #2, left side), 21 (Coolant Temperature Sensor), and 56 (EGR system). Is it likely that I've actually got three things wrong or is one of these likely to be causing the three faults? I've got no problem buying the necessary parts (maybe some problem installing them, I'm not as young as I used to be . If replacing the sensor(s) is the way to go, does anyone know the appropriate numbers to order by? How would you proceed? Thanks for any input, the combined expertise of this forum is amazing.

I'd start with the cheapest one first.

The coolant temperature sensor is between 18 and 27 dollars depending on where you get it and is easy to remove and put back in. This also happens to correlate quite nicely with the fact that your car acts weirder as the weather gets warmer. The CTS tells the ECU how warm the coolant is. If the ECU is getting bad readings, it's going to adjust the car according to those bad readings and make your car run badly.