S80 Crankshaft sensor question

UncleBoost · Post by **UncleBoost** » 21 Jan 2012, 17:00

Ok..I've brought this car back to life...the last detail is driving me Nuts tho... My question is can a Crankshaft sensor OR Camshafte Position Sensor make the engine Skip on a particular cylinder?
Vitals: Cyls 1-6 120 PSI #6 has 125 psi
Good Spark, Good fuel pressure, all injectors works as tested.
New HG, Head checked for Cracks and Shaven 18 thousandths
All valves are fine, new stems.

Symptom: NO CODES at all... Engine has a skip. pulling the coil 1 at a time for each cylinder effects the idle except Cyl 5. No change in idle when #5 coil disconnected, and reconnected.. 1-4 and 6 the engine idle is much worse but clears up when the coil is reconnected... pulling the #5 injector while idling generates an open circuit code. Also, when the coils are disconnected the Misfire codes are generated.

Question: Can a faulty Crank sensor consistently not allow cylinder 5 to Spark or inject fuel? Can the Cam position sensor do this?
I am baffled as to why #5 has no apparent operation but I have all the vital requirements for it to work....

Thanks
-= UB =-

Post by **jimmy57** » 21 Jan 2012, 19:30

No, if the CKP sensor detects rpm and crank position. CMP sensor is the way ECM knows the firing order as the cylinders that fire are different on the two crank revolutions of a complete cylinder firing sequence. CMP also is used for CVVT control.
Swap fuel injectors between #5 and another cylinder to see if the dead cylinder follows the injector.

UncleBoost · Post by **UncleBoost** » 22 Jan 2012, 07:04

Ok so CMP being the Camshaft Position sensor?... I will swap the injectors today... Also, I'd like to know (Trying to cover all the bases) If one of the turbos had a bad seal, could it possible leak water into the oil supply? I have a small bit of water coming from somewhere...i suspect one of the Twins but don't know which one or if this is even possible...ON my 850 R when one of the coolant hoses burst, all the coolant left the engine and I cooked the turbo seals, but this resulted in Oil being dumped into the Intercooler and intake system..

So If the problem does NOT follow the Injector what should be the next thing to try? I have swapped in 4 seperate coils and they all fire...
Camshaft timing.... I were 1 tooth off between the Intake Camshaft HOME postition (Marks aligned) and the V V T home position, could that create the symptoms I have or would this generate a timing related Code? I get Zero codes now related to timing...

Thanks for your reply
-= UB =-

Post by **jimmy57** » 22 Jan 2012, 09:34

Yes, CMP is cam position.
IT is possible for turbo to get coolant into water supply but the oil cooler on the back of the oil pan is several times more likely as the coolant into oil problem. Turbo would do this if it cracked and let water passage leak into oil passage.
I see no year model. Is this a 2002 or later with dual CVVT or 99-2001 with CVVT on exhaust only? I think 99-2001.
If it has no CVVT on intake then there is no CMP on that side and no codes from misalignment. There would be equal effect to all cylinders. Probably would idle OK but have low power until boost builds from being out of time on cams.

Since you have equal compression then the choices are narrowed down considerably. Coils eliminated as problem. Injectors are next. There could be wiring problem to the #5 coil but I would expect a code for that.

537playing · Post by **537playing** » 22 Jan 2012, 15:29

You mentioned you swapped four coils. Are you saying that you put four differnet coils with your #5 cylinder? And each one fired while in the fifth cylinder? I wonder if you have a wire that is frayed with the coil. The wired are bent to fit in and perhaps one wire is broken but the plastic sheath hides it.