Signs of a Crank sensor going Bad?

**M3Jokster** · 02-11-2007, 09:55 PM

well...

about 2 weeks ago, i got CEL flashed (only) in front of my eyes when i was just about to make a left turn.

well i pulled the code and it came out as Cranks sensor. I cleared the CEL...and it never came back.

the crank sensor has 100k miles so far...

what are the signs of a bad or going bad Crank sensor?

TIA.

**xjeeper** · 02-11-2007, 11:34 PM

When my crank position sensor went bad in my M3 is was pretty wierd. It would stumble and hesitate and simply run terrible some of the time and the rest of the time it ran perfect. I was so confused, it was either running perfect or hardly running at all. Sometimes the car would run mierably and then shut down completely. I would crank and crank and it just wouldnt start. I would come back 30 minutes later and it would fire right up and run perfectly. Sooner or later it would start running horibly again. (it would go from running perfect to running horribly instantly, either it was going good or it was going horrible, no in-between)

The CPS went out on my brothers jeep liberty and the symptoms were the exact same. It would either run perfect or it would hardly run at all, or even quit all together.

**M3Jokster** · 02-12-2007, 01:13 AM

thanks...
for me...i have no problems starting at all...cold or hot...

the problem i have is sometimes when i cruise...steady speeds my car might "hick-up" and hesitates. but it's once in a blue moon...most of the time it runs perfectly.

oh well, just ordered a new crank sensor and will install it sometime this week. hopefully it gets sorted out.

**ScotcH** · 02-12-2007, 01:20 PM

I had similar issues as xjeeper. Mine would sometimes be REALLY hard to start, then come back 1/2hr later, and i'd fire right up. Also, I had issues with weird revving occasionally (like the revs would go to 3k for about 10seconds then drop back down, and car would shut off). Finally, I could not get the car started at all. REplaced the CPS, and it's good as new (so far).

**M3Jokster** · 02-13-2007, 01:34 AM

well.....after i exited the freeway today...i slowed down, car died and i popped the clutch, then CEL flashed again..this time for about 1 minute or so..then went away.

checked the CEL...turned out it's the Crank sensor again. my new crank sensor is coming in a couple of days.

any pointers? do i have to remove anything i know the fan clutch and fan blade is in the way....is it possible i can remove and install the sensor w/o moving anything else?

**L3000C** · 02-13-2007, 01:37 AM

how much for a crank sensor?

**M3Jokster** · 02-13-2007, 01:39 AM

i got it off the boards...brand new...70 shipped

**Balthazarr** · 02-13-2007, 02:29 AM

CPS on S52 block is mounted at the rear is it not?

**stupenal** · 02-13-2007, 03:26 AM

Originally Posted by M3Jokster

well.....after i exited the freeway today...i slowed down, car died and i popped the clutch, then CEL flashed again..this time for about 1 minute or so..then went away.

checked the CEL...turned out it's the Crank sensor again. my new crank sensor is coming in a couple of days.

any pointers? do i have to remove anything i know the fan clutch and fan blade is in the way....is it possible i can remove and install the sensor w/o moving anything else?

i think you might be referring to the camshaft position sensor. That one is in front of the manifold, underneath the VANOS unit. That one is fairly simple to remove and replace - I think the crank sensor is a bit more difficult.

**Concentric190** · 02-13-2007, 04:49 AM

when my crank sensor went bad the car just died then didn't turn back on.

**ScotcH** · 02-13-2007, 10:24 AM

Originally Posted by stupenal

i think you might be referring to the camshaft position sensor. That one is in front of the manifold, underneath the VANOS unit. That one is fairly simple to remove and replace - I think the crank sensor is a bit more difficult.

No, on the S50 (which I assume he has ... 95 M3) it's in the front. You get at the sensor itself from underneath the motor ... mounted right above the tooth wheel on the front of the engine, about 10 o'clock looking from the front (4mm or 5mm allen bolt I think). You'll need to remove the plastic channel that runs on top of the thermostat housing, and unplug the wire from under the intake manifold (kinda behind the filter housing). Make sure you unplug the right one ... the cam position sensor plug is right next to it. I was able to do it on my car pretty quickly, but I don't have a fan or AC, so it was pretty easy to get at ... not sure about a street car. Goood luck!

**Balthazarr** · 02-13-2007, 02:28 PM

No, on the S50 (which I assume he has ... 95 M3) it's in the front.

^ He has an S52 OBD1 conversion.

**ScotcH** · 02-13-2007, 04:18 PM

Originally Posted by Balthazarr

^ He has an S52 OBD1 conversion.

In that case .... it would still be in the front, since he would have reused the S50 CPS

**Balthazarr** · 02-13-2007, 04:34 PM

Originally Posted by ScotcH

In that case .... it would still be in the front, since he would have reused the S50 CPS

Why is the S52 using this CPS when it's supposed to read from the rear of crank?

**fivaxis** · 02-13-2007, 06:29 PM

When mine went bad it would run ok at a certain rpm range and bad at other rpm, and wouldn't go past about 5500rpm. It was throwing ignition coil codes too. IIRC I just unscrewed the radiator hose to get to it. Also getting the wiring routed is bit of a pain.

**M3Jokster** · 02-14-2007, 12:13 AM

thanks guys...i have a SuperCharged 95 M3 3.2L OBD1. the crank sensor is toward the front of the timing chain cover.

S52 uses the rear CPS...there are rings on the rear crank.

thanks fivaxis..for the advice..i try not to remove any other parts..seeing if i can go about doing it from the bottom up....

wish me luck!

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