Why have cam sensor ? runs without it.

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I have a buddy with a Taurus 2002 Duratec. It was running bad. It was suggested to unplugged the cam position sensor. It ran much better. He's been driving it unplugged for months. Why have one to begin with? Why does it run better unplugged??
 
Doesn't it do something for the MPFI where it runs in "batch" without it, not specifically targetting the open valves?
 
Chrysler uses the cam sensor only during starting and then ignores it.Dont know how a Ford is ignoring it all the time.
 
I'm not sure if a 2002 Ford has EGR or not. Most current engine designs have variable cam timing such that they can adjust the overlap allowing exhaust gas recirculation without an EGR valve. This is beneficial for fuel economy and necessary for EPA.

If it runs better without that's nice. That doesn't necessarily mean it runs as well as it should, or would with a functioning cam sensor.
 
The mystery , to me, just got more so. I sent him a text and in return he claims that he installed a new one and it ran terrible with the new sensor.Back to running unplugged.

I don't understand this. It must be another component bad?
 
Perhaps the sensor allows adjustment, while running, of timing, of either the cam(s), ignition or both. With it unplugged, it allows a default position for both. It may be that one of the gizmos doing the adjusting is faulty, so the default position works better because the gizmo is not in play.
 
Don't these need to be relearned when replaced? Either the dealer can force the computer to do so or he could run it for a while and hope it "takes".
 
Originally Posted By: eljefino
Don't these need to be relearned when replaced? Either the dealer can force the computer to do so or he could run it for a while and hope it "takes".


Really, interesting, Hmmm. can anyone confirm this? My buddy installed the new one and it idled terrible. So he unplugged it.
 
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If the ECU knows Crank position, it knows where are the pistons. Without Cam position, the ECU does not know if the piston is on intake, for example, or power stroke -- it only knows the piston is on the way down (from the Crank signal). So the Cam position signal lets the ECU know what stroke the pistons are on.

I don't know details of this engine, but having Cam position would be useful for misfire detection, possibly for synchronizing fuel injection timing with the intake stroke on each cylinder, firing the right coil-on-plug ignition, etc.

Not surprising it can 'limp mode' just fine without the cam sensor, though, because the ECU can just guess one of 2 possibilities and if wrong guess the second.
 
I don't think there is a need for cam position if you already know the crank position, unless you are using variable valve timing.

Maybe it runs better because it is not running variable valve timing and something is wrong that makes the variable valve timing not running well.
 
I realize you said he has a duratec but my previous 2004 vulcan taurus had the common CPS failure. We replaced it and upon first start up it stumbled/misfired for 3-5 seconds and then smoothed right out. It ran fine for many tens of thousands of miles until I traded it.
 
It runs better with the cam sensor . Years ago when the Buick Grand National came to the marker I went to GM training classes to keep current we played around [with the grand national] and found yes it did run with out the cam sensor ,but it ran super with it.
 
Originally Posted By: WobblyElvis
According to AllData, a special synchronizing tool is required to replace the cam position sensor. If this is not done correctly engine damage may result. My guess is that when running without the sensor the computer substitutes a safe signal value [or latest signal value received] that allows the engine to run until a proper repair is made.

http://www.etoolcart.com/ford-rotunda-cam-synchronizer-ranger-taurus-windstar-303-589.aspx


Cam "sensor" is a misnomer in this case. The part that needs precise alignment is the cam synchronizer, found on the Vulcan engine family, not the Duratec. On the Vulcan, the actual sensor sits on top of the synchronizer, and gets its signal from a tab on top of the synchronizer shaft that rotates inside the sensor. No special alignment is required for the sensor, but it is critical for the synchronizer.

A lot of the time, it is the synchronizer that fails, and the sensor is just collateral damage since it often gets struck by the tab.

The alignment tool is used when installing the synchronizer using the top dead center method. You can do it by marking the position of the tab on the intake before removing the old synchronizer though and lining the new one up where the old one was. Being off a tooth won't cause damage, you just have to do it over. Being way off could be another story though.

The Vulcan is cam in block though. The Duratec is DOHC.
 
Yes Duratec with the small cam sensor on the side of the head. I think I understand how the computer defaults to a preset timing/synch map if the sensor is unplugged.Probably running less efficiently.

So my question is why does it run terrible when it's plugged in? The computer (PCM) does not like the information being sent by a plugged in sensor. Any ideas?
 
The replacement of almost any electrical component usually calls for disconnecting the battery. Has this been done to this car? Disconnecting the battery, and holding the two leads from the car together for a few seconds, might help the computer relearn the new sensor.
 
The cam sensor allows the ECU to know when #1 is coming up for an intake stroke. Then it can inject fuel, sequentially, to all the cylinders.
Without, it batch fires the injectors. Because it doesnt know if its on intake or power stroke.

Its a simple magnetic pickup. From the pictures I found, its reading a nub or ridge on the outside face of the exhaust cam. If its possible to see inside, you might try spinning the engine over by hand and looking for it. Maybe something blocking the sensor?
The only other thing I can think of, is the cam gear slipped on the camshaft or the chain jumped and now the timing is off. Does it seem down on power?
 
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I remember the cam sensor for the Duratec motors is only for starting the engine. There is no variable cam timing. Typical signs it is bad is a long crank time for starting as the PCM has to guess where the correct cam location.

I would guess there are other issues if it does not run good with a new one assuming the new one is good. Be sure the shield is good on the wire.
 
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