Cold Start problems
I've checked out the other "cold" and "no start" topics but didn't see a fix that fit my problem. As soon as the weather dips below freezing my 1990 Bonneville refuses to start. It cranks fine but coughs and sputters as if the spark isn't adequate or timed properly. The temporary fix is simple -just plug in the block heater for 1/2 hour and away it goes. Once it starts, and burns off the excess fuel, the car purrs like a kitten.
I have two other Bonnvilles, one that I am transplanting an engine into and another parts car. Yesterday I had both Bonnevilles in the driveway, I cranked the problem car until the battery died and it wouldn't start. I hopped into the one I'm working on and it fired up right away. I plugged the problem car in (along with a battery charger) and was able to start it 1/2 hour later.
Since I have a parts car available I am able to swap parts easily and, so far, have replaced the following items in an effort to solve the cold start problem.
ECM, Crank position sensor, coil pack, plugs and wires (new ones) and a temperature sensor. I read somewhere that the ECM uses the temperature sensor and the crank position sensor to determine the fuel mixture and spark timing during the cold start process so I swapped both, no improvement. There appears to be two temperature sensors on this car located beside each other, one has a two terminal wire harness and the other a single post threaded terminal. I changed the two terminal unit, does anyone know which sensor is used by the ECM? (Yes I plan on changing the other one now).
I haven't checked the fuel pressure, the car seems to be getting lots of fuel and I suspected ignition / timing was the problem but perhaps the low pressure will cause fuel to be delivered but the spray pattern isn't proper? Any ideas.
The strange thing is that the car starts and runs so well after a short period on the block heater.... Any thoughts