Crown vic problem

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A crown vic we have has stalled twice now in the past week. This only occurs when I place the vehicle in reverse, and then turn the wheel hard either way. If I turn it all the way right for example, the engine shudders for a split second and then stalls. What could this be?

They have already cleaned the "air sensor" and checked the throttle body.
 
What year?
How many miles?
Did you check for vacuum leaks?
When was the last time you cleaned and regapped (or replaced) th spark plugs?
How about the spark plug wires?
Did you check for codes?
Did you check the power steering switch that's supposed to bump up the idle when you turn the steering wheel like that?
How many miles in the IAC?
 
The putting into reverse thing (thus changing the angle of the engine/tranny) makes me think possibly that bad engine mounts are somehow involved (and thus causing the engine to rock too far one way or the other and affect another system). But that is just something that I came up with uninhibited by the thought process.
 
I suspect the IAC motor is not opening properly or the passage is dirty.

When you turn the steering wheel all the way to the stop, the power steering pump builds the most pressure, and that slows the engine down. A properly functioning IAC system will react by opening up to allow the RPM to stay the same.

If the throttle body has already been cleaned, then this goes further to prove that the IAC system is the problem.
 
Could be the IAC (Idle Air Control) valve; common on older Fords to get gunked up. Or a bypass valve in the power steering that allows too much pressure to build.
 
Originally Posted By: zzyzzx
What year?
How many miles?
Did you check for vacuum leaks?
When was the last time you cleaned and regapped (or replaced) th spark plugs?
How about the spark plug wires?
Did you check for codes?
Did you check the power steering switch that's supposed to bump up the idle when you turn the steering wheel like that?
How many miles in the IAC?


I think he's talking about his Department's Police Car!
 
Originally Posted By: Merkava_4
Originally Posted By: zzyzzx
What year?
How many miles?
Did you check for vacuum leaks?
When was the last time you cleaned and regapped (or replaced) th spark plugs?
How about the spark plug wires?
Did you check for codes?
Did you check the power steering switch that's supposed to bump up the idle when you turn the steering wheel like that?
How many miles in the IAC?


I think he's talking about his Department's Police Car!


Which still doesn't answer the questions.
 
If your throttle position sensor is wacky and gives a reading that's sometimes not matching the reading when it first starts, but is still plausible, it won't throw a code but also won't know that the computer is responsible for proper idle speed.

But one would have to watch live data when it happens for a firm diagnosis.
 
My Dad's '97 Thunderbird was acting similar. The solution was to find and fix vacuum leaks. Not hard to do. Anything rubber around the intake manifold is suspect. In my case, the PCV grommet in the valve cover had become rock hard with age. I replaced it and all other vacuum lines and that solved the problem.
 
Starting 2005, all Panther platform vehicles got DBW, which eliminated the IAC and the cruise control module. If this is a Police Interceptor, it will not have variable steering assist either, so that eliminates that issue. As mentioned before, we need to know the year.

Does this happen when the engine is at operating temperature or when the engine is cold? Is the PSF up to level?

To add to what's previously been mentioned - MAF and/or harness and MLPS come to mind. I would check the MAF voltage. which should be in the 0.6V - 0.75V range. Anything higher, the MAF is contaminated or faulty.
 
I would also look at the serpentine belt, and any other accessory belts, and make sure they are in good shape, and tensioned properly. Make sure the pulleys are in good shape, and the driven accessories (water pump, generator, steering pump) are all in good shape.

BC.
 
Something simple probably on a good ole 4.6
wink.gif
 
Originally Posted By: JDW
Something simple probably on a good ole 4.6
wink.gif



Most likely, but depending on the year it could be an IAC, or a Fly-By-Wire throttle body.
 
Also, a cleaned MAF sensor does not mean its good. Try running with it unplugged. Itll run off of default tables programmed into the PCM. On my '04 the only thing I notice is the trans shifting a little harder (likely the default tables overestimate load, to be safe.)
 
It is a 2009 CVPI. Rattles like no tomorrow also... Doesn't come from the engine, just the body in general.
 
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