Camshaft Position Sensor.

[Dave Lindsay]

1998 Z3 1.9L , 65,000 miles.
When I was replacing the serpentine belt I noticed that the belt had chaffed and shorted the CPS cable down to bare copper. So I snipped the cable and isolated the conductors. Engine pulls really well but has a rough idle.

The cable was improperly routed and I also suspect that the cable had gotten pinched by the belt as well, because a slight tug and it pulled out of the sensor. New CPS coming in the mail.

Would this be the cause of the Rough Idle?

 

[colb]

Could well be the cause, CPS is a really important sensor can affect running if failing and be the cause of a non starter if completely duff. Hope you got a OEM replacement, cheap pattern parts are not such a good idea.

 

[littlefeller]

mine wouldn't run with a duff sensor, left me stranded. I brought a cheap replacement, fitted it then went for a drive, after about 1 mile it just cut out. it would start but just kept cutting out.
mine still idles a little rough even with the new sensor though.

to be fair most M44 engines sound a little lumpy

 

[Dave Lindsay]

mine wouldn't run with a duff sensor, left me stranded. I brought a cheap replacement, fitted it then went for a drive, after about 1 mile it just cut out. it would start but just kept cutting out.
mine still idles a little rough even with the new sensor though.

to be fair most M44 engines sound a little lumpy

Thing is, my CPS is disconnected ! And it runs great and is smooth off of idle !

 

[t-tony]

Not sure how that could be unless it's in "limp home mode" and running solely off the crank sensor. You would notice a huge difference with a cam sensor in the circuit I'm sure. Can you post some pictures please?

Tony.

 

[Dave Lindsay]

Not sure how that could be unless it's in "limp home mode" and running solely off the crank sensor. You would notice a huge difference with a cam sensor in the circuit I'm sure. Can you post some pictures please?

Tony.

CPS is still in the mounting hole, but damaged cable has been snipped of and wires isolated with heat shrink. Only thing I can think of is a 'hack' further towards where it plugs in. But I am not peeling back the upper manifold until the sensor arrives. At that time I will post photo's.