# engine shutdown mystery



## bummedoutjohn (Jun 11, 2019)

97 maxima, 134,000 miles. (I have invested over $1600.00 in this problem so far, even many days in the hands of a reputable mechanic): When driving or even idling in park, once engine heats up (15 mins driving, 25 mins. parked) the engine will stop. It will restart immediately. No engine codes. I have replaced the computer, fuel pump, fuel filter, fuel press regulator, most of the engine sensors (even though no codes), even completely drained and refilled fuel tank. The car runs smooth and strong, then stops. I have noticed it occasionally struggle when decelerating trying to keep idle speed-(drops too low-I have to "catch it" with accelerator) When this shutdown occurs when parked there is no swing in idle speed-just an abrupt shutdown. After all of this both the mechanic and I are left scratching our heads. After all of this money, I am hesitant to put another dime into it. I have not replaced coil packs or plugs (another $130.00 plus shipping) even though mechanic indicated he doubted trouble here. Any direction here would be appreciated.


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## smj999smj (Jan 1, 2006)

If you can duplicate it on a consistent basis, I would install a fuel pressure test gauge and run the engine until it stalls, to see if the fuel pressure could be the issue. If it stalls and the fuel pressure is still at 34-36 psi, you can fuel out a fuel pump issue. I've also installed timing lights and run the vehicle to see if the spark cuts out (put the clamp around the harness of one of the front coil packs (you'll need to remove the cover over the coils). Cam position sensors and crank position sensors can cause stalling or misfiring, especially when they get hot, but not always trigger a code. I'm assuming you already replaced them since you mentioned replacing "sensors." A sticking EGR valve could also cause stalling. Another problem that sometimes occurs is breaks in the engine harness where it creates a bend between the engine and the firewall. With the engine running, grab the harness and move it around and see if you can cause the engine to cut out. If so, there may be a broken wire making an intermittent contact inside the harness. That said, those issues usually trigger a trouble code. As with anything, I prefer to confirm a part is actually bad rather than just swap parts out until something fixes it.


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## bummedoutjohn (Jun 11, 2019)

Thanks for the info. Will give your suggestions a try. may be a few days before i get the time.


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## bummedoutjohn (Jun 11, 2019)

*coil packs test ok using method you describe. fuel pressure is ok-mounted gauge and drove until stall-still ok. 

*The next day I started car while parked and let it idle-at about 22 mins idle time it just stoped-no sputtering or idle speed swings-just stopped. Different from driving shutdown. restarted immediately.

*When this occurs during driving, it seems to have trouble finding correct idle speed during deceleration after high speed(slowing down for stop light) When idling at light, it will start to slow, as if fuel trouble or trouble maintaining idle speed, and then stop. Will immediately restart. Can prevent shutdown by using accelerator pedal to increase engine speed. During a 45 minute drive in town and on highway, the shutdown occurred 3 times, first time after driving for about 20 minutes.

*Only seems to happen when engine and components are hot

Trying to figure out where fuel pump relay is located-someone told me that these also have cold solder problems. My manual says behind a kick panel but no pictures provided.

*Still no codes.


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## bummedoutjohn (Jun 11, 2019)

*solution found*



smj999smj said:


> If you can duplicate it on a consistent basis, I would install a fuel pressure test gauge and run the engine until it stalls, to see if the fuel pressure could be the issue. If it stalls and the fuel pressure is still at 34-36 psi, you can fuel out a fuel pump issue. I've also installed timing lights and run the vehicle to see if the spark cuts out (put the clamp around the harness of one of the front coil packs (you'll need to remove the cover over the coils). Cam position sensors and crank position sensors can cause stalling or misfiring, especially when they get hot, but not always trigger a code. I'm assuming you already replaced them since you mentioned replacing "sensors." A sticking EGR valve could also cause stalling. Another problem that sometimes occurs is breaks in the engine harness where it creates a bend between the engine and the firewall. With the engine running, grab the harness and move it around and see if you can cause the engine to cut out. If so, there may be a broken wire making an intermittent contact inside the harness. That said, those issues usually trigger a trouble code. As with anything, I prefer to confirm a part is actually bad rather than just swap parts out until something fixes it.


I discovered that there are two problems with the throttle body: 
1) the rod that holds the fast idle cam is not allowing the adjustment screw to mate properly with the fast idle thermostat-had to put quite a bend in the screw mount to get it to set in the center-it was slipping off when hot and this would cause the engine to stall.
2) the "thermostat that drives the fast idle cam is not making full travel. when set to proper mark when cold, it is out of alignment when hot. when readjusted when hot to the correct mark, it is misaligned when cold.
i have made a "best average" set to the adjustment screw that prevents the stall and will see if i can live with it. just have to let it warm up really good before i drive it.
the only new replacement complete throttle body i can find costs 430.00.


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