Fires but does not start...with solution

[57wayne]

Saturday morning, after two weeks below freezing my daughter's 98 C70 did not start. Fired but no start. Sometimes it would idle poorly but stall if the accelerator pedal is pressed.
Checked fuel pressure. Good.
Swapped MAF sensor. No change.
Checked diagnostics and found a Failed ECT code. Previously, it was giving a fault for out of range or some signal issue but ran fine.
I had a new temp sensor but since it was 0 degrees out, and a little tricky to get at, I plugged the new sensor in and put a block of snow on it. Started just fine. As it warmed up and the speed picked up, I took the snow away and held the sensor. As it warmed, engine speed dropped.
With it running, I got it inside and changed the sensor.
Easiest way to do it is remove the upper hose and thermostat housing. Now you can get a wrench on the sensor. Swap it out; remember to pull the aluminum washer and swap it.
With that all done, started and ran...but still not right. Turned out the MAF I swapped in was not good and caused a code telling me the turbo charger waste gate solenoid failed. While troubleshooting that, I unplugged the MAF, and forgot to plug it back in. Car was running pretty good, but icarsoft tool said I had a weak signal. Found it unplugged and plugged it back in. Car died instantly. Swapped back to the original and car is back to running fine.
I did not see other reports of no start because of the ECT sensor. When the sensor fails, default is to assume warm temp, and not provide extra fuel. On a cold day, that will allow the car to fire but die instantly. Case solved. Hope this helps someone.

[scot850]

This has been documented many times, but maybe not as well as you have done here. Also the extra cold temperature will make the issue way worse. If you live in a warm area you may not notice the issue for a long time if ambient temps are high. Good catch and what a bugger that the replacement MAF was bad too. Well done that man!

Neil.