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crankshaft position sensor - more to it than startup?


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Car specs: US spec 1998 Boxster, manual transmission, 67k miles

Symptoms over last 6 months: (1) engine running 10 - 15 degrees over "normal" (recently, even on cold days); (2) idle is "hunting" over a 100+/- rpm range (even after cleaning throttle body - which cleaning resulted in "average" rpm of 1000 on dash tach); (3) last Friday, for the first time, at start-up engine turned over but would not start - on 3rd try, it started. Once running, engine performs and sounds "normal".

Review of forum on some of these symptoms: faulty (or failing) crankshaft position sensor?

Any thoughts?

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Car specs: US spec 1998 Boxster, manual transmission, 67k miles

Symptoms over last 6 months: (1) engine running 10 - 15 degrees over "normal" (recently, even on cold days); (2) idle is "hunting" over a 100+/- rpm range (even after cleaning throttle body - which cleaning resulted in "average" rpm of 1000 on dash tach); (3) last Friday, for the first time, at start-up engine turned over but would not start - on 3rd try, it started. Once running, engine performs and sounds "normal".

Review of forum on some of these symptoms: faulty (or failing) crankshaft position sensor?

Any thoughts?

I also have a 98 - 5 speed. Have you been able to see if there are any fault code(s)?

Also put your key in and turn but don't start or turnover the engine to determine if all your gauge warning indicator lights are all working. Including the red lights by 250 mark of your temperature gauge and the 0 mark of your fuel gauge. Your top light (lower far right) and the two red temperature and fuel gauges automatically go out shortly after the key is turned on. I am curious why your temperature is running high?

9a31ed0e.jpg

It definately sounds like a sensor going bad. You probably saw this link. HERE it is just in case you haven't.

:welcome: to Renntech!

Edited by kbrandsma
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Car specs: US spec 1998 Boxster, manual transmission, 67k miles

Symptoms over last 6 months: (1) engine running 10 - 15 degrees over "normal" (recently, even on cold days); (2) idle is "hunting" over a 100+/- rpm range (even after cleaning throttle body - which cleaning resulted in "average" rpm of 1000 on dash tach); (3) last Friday, for the first time, at start-up engine turned over but would not start - on 3rd try, it started. Once running, engine performs and sounds "normal".

Review of forum on some of these symptoms: faulty (or failing) crankshaft position sensor?

Any thoughts?

I also have a 98 - 5 speed. Have you been able to see if there are any fault code(s)?

Also put your key in and turn but don't start or turnover the engine to determine if all your gauge warning indicator lights are all working. Including the red lights by 250 mark of your temperature gauge and the 0 mark of your fuel gauge. Your top light (lower far right) and the two red temperature and fuel gauges automatically go out shortly after the key is turned on. I am curious why your temperature is running high?

9a31ed0e.jpg

It definately sounds like a sensor going bad. You probably saw this link. HERE it is just in case you haven't.

:welcome: to Renntech!

I checked the dash lights . . . all come on & go off as noted. This last weekend, I checked for fault codes with my Durametric . . . no fault codes! Also, I took the time to give the sensor and its wiring harness and connector a visual inspection . . . all appear to be in good condition.

Could my "turning-over; no-start" incident be just a fluke . . . i.e. DME hiccup? Something that may come again, but with no regular frequency and thus, no indication of a pending component failure . . . just a "typical" computer-age computer glitch?

Also, as to my other symptoms . . . I am wondering whether or not they might be related to a failing crankshaft position sensor . . . particularly, if the DME continually monitors the pulse from the sensor and if so, any hiccup in the sending of an expected pulse could "confuse" the DME!? If the DME does a continual monitor of the sensor output and all of my symptoms are "possibly" inter-related, then a new sensor is in order. Any thoughts?

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I do not know if Durametric can read the CPS but a PST2 or PIWIS tester can.

I have seen a CPS be intermittent and work fine when the engine was cold but as it heated up the CPS would fail and shut off the fuel pump (via the DME).

You can manually check the CPS by:

1. Remove connector. Connect ohmmeter to CPS connector, pins 1 and 2. Display at 20 °C: 0.8 - 1.0 kohms.

If this is not the reading then replace the CPS.

2. Connect an ohmmeter to CPS connector, pins 1 and 3. Display: infinite ohms.

If this is not the reading then replace the CPS.

If these readings are okay then the CPS is likely ok.

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I do not know if Durametric can read the CPS but a PST2 or PIWIS tester can.

I have seen a CPS be intermittent and work fine when the engine was cold but as it heated up the CPS would fail and shut off the fuel pump (via the DME).

You can manually check the CPS by:

1. Remove connector. Connect ohmmeter to CPS connector, pins 1 and 2. Display at 20 °C: 0.8 - 1.0 kohms.

If this is not the reading then replace the CPS.

2. Connect an ohmmeter to CPS connector, pins 1 and 3. Display: infinite ohms.

If this is not the reading then replace the CPS.

If these readings are okay then the CPS is likely ok.

I'll test the CPS this weekend and let you know what I come up with. Just out of curiosity, do you know if the slightly elevated operating temperature and hunting idle are related to a failing CPS?

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  • Admin

I do not know if Durametric can read the CPS but a PST2 or PIWIS tester can.

I have seen a CPS be intermittent and work fine when the engine was cold but as it heated up the CPS would fail and shut off the fuel pump (via the DME).

You can manually check the CPS by:

1. Remove connector. Connect ohmmeter to CPS connector, pins 1 and 2. Display at 20 °C: 0.8 - 1.0 kohms.

If this is not the reading then replace the CPS.

2. Connect an ohmmeter to CPS connector, pins 1 and 3. Display: infinite ohms.

If this is not the reading then replace the CPS.

If these readings are okay then the CPS is likely ok.

I'll test the CPS this weekend and let you know what I come up with. Just out of curiosity, do you know if the slightly elevated operating temperature and hunting idle are related to a failing CPS?

CPS issues usually do not affect engine temperature or idle. Usually when the CPS is failing (or intermittent) the engine stumbles or stalls.

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