Join Date: Sep 2008
Location: Fruitland Park,Florida
I'm not talking about reading codes when I suggest a running sensor scan. A good scanner can read sensor data with engine running, or some data with ignition switch on. The coolant temp sensor CTS has a reasing with engine running or with ignition on. The problem with your car was that cts was reading very low compared to actual coolant temp. This was when car was running, but rich.
The low temp reading by cts was causing pcm to add much more fuel, as needed in very cold weather. When cts failed altogether, it read around 0 degrees and engine would not run. You made a good guess changing the cts. But you could have guessed wrong and spent money on a part that didn't need replacing.
The whole purpose of a running sensor scan, is to let you see what data the sensors are displaying under different running conditions. Once you learn what is normal readings for different conditions, seeing data out of spec can help pinpoint trouble area.
Those in the know, still don't rush out and change the part indicated. They check wiring, connectors, grounds, & splices, before assuming the part is defective.
As an example, my 90 3.1 v6 car has a map sensor connector that makes poor contact from time to time. The symptoms are a mis and jumping rpm. This gets worse & worse until engine won't run when trans shifted from park. Taking the connector off the map & reinstalling it solves the problem, until the next time connection gets bad. One day I'll actually change the connector pigtail.
Your car being 26 years old, means that many problems will be electrical, vacuum lines leaking, etc.