Hi.
Re:"when gas pedal depressed, the car would stall...once you babied it to about 300 rpm it would seem to clear."
There are conditions and inputs that are used by the PCM (main computer, also called ECU or ECM- This determines the mixture sparyed inside cylinders). Some ov the inputs, like air temperature are used in a different way when engine is cold or when idling, some factors that contribute to determining the mixture proportion, like recirculated gases from exhaust for example. For this reasons when you rev up to 300 rpm, the engine will stay on.
If additionally the engine is turning off when you put in gear, then there may be a problem affecting the auto transmission. Engine stalls in gear because the wrong gear is getting engaged by auto tranny module (called TCM).
About idle problem, parts to be checked are the following:
Fuel pump, fuel pressure and fuel circulation: use a hand gauge to test fuel pressure (eg. Vacuum & Fuel Pump) . If there is a problem, parts that can be involved are pump, lines and filter.
Vacuum system makes a bigger difference when car is idling. A vacuum leak will result in a lean mixture, causing start problems. Look for vacuum leaks. This is done using the same gauge you used on fuel lines, while spraying carb cleaner on lines. If there is a leak, pressure will go up.
Air sensors, MAF(mass flow sensor), IAT(intake air temp.), along with air intake problems can cause problems like the ones you described. A rudimental test can be done disconnecting sensor connectors one at the time, and observing if this make any difference. If it does not make any difference, then the sensor is probably defective. Sensors like MAF and MAP sometimes can be sorted out by cleaning them.
Crank sensor can cause problems.Check its connector. Malfunctioning or disconnected crank sensor will result in severe timing problems.
Ensure that there is spark in all cylinders. This is done pulling out cables one at time, and putting them near to engine. Listening to engine a you should also be able to realize if a cyl. was not firing when pulling out cable (no change).
If additionally there are tranny problems, parts like TPS or other parts contributing in TCM input and transaxle control must be tested.
There are more factors that can cause engine not starting, I have listed most common faults that may apply to your problem. The first thing to do is a code scanning. Use an OBDII scanner, or go to the nearest Autozone, they do the code scanning for free.
If there are no codes, do all the troubleshooting described above, most of the time this will be enough to allow you finding the problem.
All the best.
Ginko.
http://schematicsdiagram.blogspot.com/2011/12/van-emits-whitish-bluish-smoke-and-bad.html
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White smoke and Acrid Smell?
http://whoisbyme.blogspot.in/2012/07/white-smoke-and-acrid-smell.html
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Car stalls and throws white smoke from exhaust?
http://repairhelpcenter.blogspot.com/2012/01/car-stalls-and-throws-white-smoke-from.html
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This will help.
Thanks.
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