Mechanics

STALLING

1990 Chrysler New Yorker

Engine Performance problem
1990 Chrysler New Yorker 6 cyl Front Wheel Drive Automatic 15400 miles

My New Yorker stalls, usually when I am slowing down. Sometimes when I`ve only driven it a few minutes, or sometimes when I`ve gone several miles. Below is the work that has been done on it recently:
1. Replaced battery
2. Diagnostic check of the engine tested well.
3. Replaced fuel pump, as the pressure was at 42 psi and the specs said it should be 50.
3. Replaced fuel filter
4. Replaced air filter
Please help !
Thanks.'.
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Rzanon
February 25, 2010.




Stop at item number one. Simple cause; simple fix.

Whenever the battery is disconnected or run dead, the Engine Computer loses its mind. It must relearn " minimum throttle" before it will know when to be in control of idle speed. Reprogramming the computer is extremely difficult. To meet the conditions the computer looks for to do the relearn procedure, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals. That's it.

As a point of interst, you did not need a new pump or filter. 99 percent of pumps that fail do not start up. Once running, they will continue to run. Fuel pressure is determined by the regulator on the engine's fuel rail. The regulator has a vacuum hose attached so it can change pressure according to load on the engine. When coasting, manifold vacuum goes way up. That vacuum is pulling fuel out of the injectors and because it's pulling much harder, there would be an excessively rich mixture. Fuel pressure is pushing fuel through the injectors. Since vacuum is pulling harder during coasting, fuel pressure goes down to offset the extra force on the fuel. If the engine was running, the pump was working.

To test the pumps capacity to develop pressure, it must be tested with the vacuum hose pulled off the regulator and plugged. The specs mean the pump should be capable of 50 psi, but it wont run at that pressure most of the time. GM cars and trucks have a lot of running issues with low pressure from worn pumps. That's almost unheard of on a Chrysler product.

Other than the diesel trucks, you will never solve a running problem by replacing a fuel filter on a Chrysler product. It's fine for a maintenance thing, but it will never solve a problem. Related to that lower fuel pressure during coasting, since the regulator offers less restriction to the extra fuel that just goes back into the tank, more fuel flows through it during coasting. The lowest volume of fuel flows through the filter during hard acceleration, so a plugged filter would show up when coasting, when the engine hardly needs any fuel.

Caradiodoc

Caradiodoc
Feb 28, 2010.


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