Expert: Sean Halliday - 11/29/2007

Question
QUESTION: my car runs for about 10 mins and then dies. we have replaced many things, such as... fuel pump and filter, crank sensor, coil pack, computer and the box next to it, altinator, battery, plugs and wires, we checked the fusible links, fuses (good) , injector palse, EGR valve... those seem to be okay... if you have any suggestions please help.

ANSWER: When it runs,does it run ok or hesitate and splutter.If you start it again or try to,does it start right away?.Im thinking fuel as if it was spark it wouldnt start at all.So,try your fuel pressure regulator and check the fuel pressure while the car is running.Try to keep the pressure tester on the engine and watch it when the engine dies.If the pressure drops suddenly,then your problem is in the fuel system.The only time i  have ever seen this was on a Oldsmobile and the computor PROM was at fault.It goes between the plug in and the computor..

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QUESTION: Ok here is the deal, it runs for about 20 to 45 minutes and then shuts down no matter what rpm range it is at. When it shuts down it acts as if it is going to restart but doesn't. It restarts fine avfter the engine cools off completly. The car has plenty of power and no hesitation at all. I even disconected the o2 sensor on the manifold to see if that was the prob but it was not. I think that something is shutting the computer down rather than the fuel system. It seems to be am imermitten problem because the run time varies each time it warms up. This last time with the o2 sensor disconected it got a longer run time! 45 minutes. Most of the time it is around 20. Thanks for the info.

Answer
Thats a new one i havnt seen.If i was working on this car,i would think its the fuel pump but,you say you fitted a new one.So,if the fuel system is tested and its got good pressure the only thing i can think of is the MAP sensor is failing when the manifold heats up.Then when it cools it is ok.The MAP is the manifold absolute pressure sensor on the firewall by the windshield,  but you will need to look as it varies position on different cars.If you replace this and its still the same then i would say you need to have to pay the dealer to have it diagnosed with their fancy hardware.I know its a last resort but i have never came across this.I have only heard of a similar problem with a BMW and the car wouldnt run.It started but shut off after a few minutes and the problem was the exhaust system.Bad catlatyic convertor.