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How can I tell when my Crank Position Sensor is going??

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Old Oct 11, 2016 | 06:56 PM
  #1  
JimmyChooToo's Avatar
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Default How can I tell when my Crank Position Sensor is going??

2003 Disco II, 85k

3 times today at low speed stop and go traffic, the check engine light comes on very briefly, RPM drops below 800 suddenly and the truck acts like it's about to stall but doesn't. Is this most likely the CPS is about to go, the battery is lowor fuel pump or even something else??

Thank you very much !!
 
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Old Oct 11, 2016 | 07:13 PM
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The CKPS does not typically trigger any codes nor does it cause the engine to stumble. The engine simply dies. Immediately. With no warning. Like turning off a light switch.

Happened to me 5-1/2 years ago on a Sunday morning with six boy scouts in the truck headed home from a camping trip. Happily it happened at a stop light and not while moving.

After the truck dies it can often be started after the sensor has an opportunity to cool down. Mine restarted a couple of times but shut down fairly quickly after. I may have made it a mile or two each time before giving up and having it towed and having a parent come rescue us.

That said, I don't have any good ideas what's causing the problems with your truck but I doubt it is the CKP sensor. Get the check engine codes read and go from there. Good luck.
 
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Old Oct 11, 2016 | 09:19 PM
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Originally Posted by mln01
The CKPS does not typically trigger any codes nor does it cause the engine to stumble. The engine simply dies. Immediately. With no warning. Like turning off a light switch.

Happened to me 5-1/2 years ago on a Sunday morning with six boy scouts in the truck headed home from a camping trip. Happily it happened at a stop light and not while moving.

After the truck dies it can often be started after the sensor has an opportunity to cool down. Mine restarted a couple of times but shut down fairly quickly after. I may have made it a mile or two each time before giving up and having it towed and having a parent come rescue us.

That said, I don't have any good ideas what's causing the problems with your truck but I doubt it is the CKP sensor. Get the check engine codes read and go from there. Good luck.
This is spot on.
 
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Old Oct 12, 2016 | 05:59 AM
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Will confirm the sudden failure, I got stuck on an Interstate exit ramp with no warning. My wife hasn't liked the Rover since...
 
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Old Oct 12, 2016 | 11:49 AM
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Thanks everyone. I think my symptoms is more like the throttle position sensor is going bad since no one thinks it's the CPS. The TPS is a $15 part, so worth a try for me. I'm paranoid to drive it now until it's fixed. I don't want to be stranded with a $200 tow.
 

Last edited by JimmyChooToo; Oct 12, 2016 at 12:00 PM.
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Old Oct 12, 2016 | 03:45 PM
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It could also be the MAF. To me, the MAF is a gremlin. Mine has acted like that and sprung back to normalcy when I swapped in a different MAF.

But hope for the TPS.
 
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Old Oct 13, 2016 | 05:56 PM
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maybe have the codes read since the check engine light came on. Better then guessing and throwing parts at it.
 
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Old Oct 28, 2016 | 10:04 AM
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Just wanted to give everyone a quick update.

I changed the spark plugs (Champion), changed TPS, cleaned the throttle body and idle control valve, cleaned the MAF and nothing. It actually got worse. I still had the sudden rpm drops and about to stall in stop & go traffic. It was driving me crazy.

I was very disappointed. Took the truck to Walid at Loudoun RoVa this morning. He tightened my battery cables and everything is running great again (except for my slipped sleeve of course). He's pretty awesome!!
 

Last edited by JimmyChooToo; Oct 28, 2016 at 10:06 AM.
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Old Oct 28, 2016 | 12:04 PM
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Another quick way to diagnose CPS is to dump water on it. Cools it down enough to restart the car.
 
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Old Oct 28, 2016 | 12:16 PM
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Thank you, for passing on the fix. I've had this happen on several vehicles over the years (I'm a fleet mechanic), but normally you'll get a code for low voltage at the ECM. Did your mechanic get a code describing this issue?

This is another reason to keep your battery cables clean and tight. Your vehicle depends heavily on good voltage.

Brian.
 
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