4 months ago van engine shut off going 60 miles an hour. pulled over and car would crank but would not turn over. Oil and gas okay. towed car home and car started right up. next morning car would again crank but would not turn over and start.towed to mechanic and car started. they checked spark plugs, wires, compression and car started every time they turned key. I drove off and car shut off going 30 miles an hour.Again try to restart, and it cranks but will not turn over. 2nd mechanic said fuel pump and filter bad.So put in new fuul pump and filter. drove 10 days and car dies going about 50 miles an hour. Again, on side of road , car cranks, will not start after numerous times. Tow back to mechanic,keeps for 3 days and drives and starts perfect everytime. Take home and car won't turn over the next morning. Take back to mechanic and he puts in a loaner distributor. Car starts and he runs it and turns off and on for 1 day. Take car home, drive for 10 days, car AGAIN won't start. cranks, but won't turn over, just like before. tow back and check with new ignition coil slave, cranks,but won't turn over.Please advise if it could be the PMC or ASD. 3 different mechanics at a loss. There is an engine light code po743, but they say this has nothing to do with this engine not turning over and shutting off while drive 50 mi an hour. Please help. Not sure what to check and how to check. Car at mechanics, but he has given up and we welcome any advice you can offer. I have new battery, new wires to battery, all fuses in fuse box right side by wheel well, check okay, new spark plugs, wires, rotor, new loaner distributor, new fuel pump/filter, oil changed, new timing belt/water pump.
Hi Jacob, There are 2 possible types of devices that cause this: a hall-effect based sensor (the cam or crank sensor) or the exhaust gas recirculation valve. When a hall-effect sensor is beginning to get weak it will often temporarily cease to pulse sufficiently to generate the signal needed to produce the spark or fuel injector pulsing from the computer. This usually happens after driving for a while when it starts to get warm and then is acts up. Usually after it cools down for a few mintures/hour or so the pulsing goes back to normal and the engine will run. The only unusual thing that you mentioned was when it won't start after cooling down overnight. That is usually a sign that it has given up entirely and would set a fault code (0720-crank or 0740-cam). It can be detected by applying a voltmeter to the signal wire of the sensor(s) and the sensor ground wire and turn the engine over by hand by means of a socket/breaker bar on the crank pulley bolt. Ideally you would observe the voltage to pulse between 5V and 0.3V which would be normal, or not which would say the sensor is not working at the present time. As it gets worse the sensor would finally go bad enough to set the fault listed above and it would no longer be intermittent. The other cause would be an exhaust gas recirculation valve which is gummed up such that when it is called upon to close (when slowing down, when starting) instead it hangs up slightly ajar. The valve is located in the exhaust pipe that crosses over from the front exhaust manifold to the rear. It has a round vacuum-operated valve actuator on the top, the body of the valve connected to the pipe, and between those two parts is a flange and inside that flange you will see the valve stem with a slot around the circumference. You can test the action by putting tip of a screwdriver in the slot to move it back and forth. There is internal spring-action that tries to close it, but if it is gummed up the stem will not move freely to the closed position. Spray some WD-40 on the stem where it enters the valve body and work it back and forth to loosen up the action. That will alleviate the ajar situation which when happening leans out the mixture too much to allow idle or starting up. If you let up slightly on the gas pedal while going on the highwauy that is when is will often hang up instead of closing which causes the engine to die and refuse to start. Other than waiting for a fault code to finally set, these are the possibilities. You can check for fault codes using the ignition key:"on-off-on=off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which remains "on", to see it begin to flash, pause, flash, etc. Count the flashes before each pause. Then do it again to be sure of an accurate set of flash counts. Let me know what find and we'll go from there. Roland