N20 Cam timing
I've got this Z4 that was towed in for a crank no start. It had the codes listed above. I cleared faults and none have returned. I performed the valvetronic functional test with autologic and it returns with no faults found. I can hear the valvetronic mechanism operating but haven't confirmed it visually. Compression is low across the board. Cyl 1 - 75 psi Cyl 2 - 70 Cyl 3 - 115 and Cyl 4 - 70. All spark plugs were fuel fouled.
Question is does anyone have a known good cam crank waveform while cranking for an N20? I've attached the capture from this car.
Just look through the oil fill hole and if the timing chain is loose it’s toast. I’ve had a few that still ran you could pick up the chain with a 90 degree pick more than 1/2 inch
I've visually inspected through the oil fill and it doesn't appear to have any slack. Thanks.
disregard previous post. used a 90 degree pick and chain is very loose. Thanks.
This engine (particularly in the first couple of years of production … is known for timing chain guide failures. Cam timing is the next place to look, particularly with the cam/crank correlation code.
I don't have a correlation code. I believe the air mass code was set due to a broken pipe at the turbo, but I don't think this is the cause of my no start. I haven't been able to duplicate the valvetronic fault. I'm just looking for a way to verify cam timing without pulling the valve cover and installing all the special tools. The shop I'm at has them if needed, but I'd like to avoid it if…
No matter what else happens, somewhere in this repair procedure you will need to address the low compression. Since all four cylinders are low, the cam timing suggestion still seems to be a good direction to follow.
Low compression may be caused by the fuel washing the rings out from continous attempted starts. you may spray a bit of oil in the cylinders and retest compression. but also the n20 engine does have common issues with the vanos actuators( part of the cam sprockets ) the bolts of the actuators loosen or break check this as well.
When the bolt breaks does it cause the camshaft not to turn?
No but it does allow for slack, so make sure to check these before re assembly
I assume the yellow trace is the crank sensor output. It should not have random gaps and random length pulses. I suggest that you recheck that.
Here's a better capture from this morning.
Channel B - intake Channel C - exhaust Channel A - crank
I haven’t found a cam crank capture. Low compression is a sign of intake valve out of time but, yours is lower than I would expect. If you can do an in-cylinder pressure capture the valve timing could be analyzed. Did you go to the PICO library to look for a cam/crank?
Unfortunately for me I don't have access to an in cylinder pressure transducer. I also didn't find anything in the Pico library. However, I was able to find a capture on iatn. Not sure if it was taken while cranking or at idle, but the intake cam on mine seems to have shifted pretty far to the right of their known good. Their capture showed both cam signals perfectly synced. The TDC trigger in…
I agree with Stephen. From what I could find if the yellow trace is your crank sensor then something is not right. Maybe your connection came loose during testing. Chris
Zoom in on crank sensor, scope may be aliasing
Not zoomed on enough for that scope. Missing pulses due to dots per time frame.
Hey Nicolas, I don't know if you have any feedback on this vehicle or not. Timing chain guides and chain stretch is an issue on these engines. Also the Valvetronic motors fail and stick at minimum lift. Not enough air to run the engine on a restart. This also affects the compression readings. One symptom is when the ignition is turned on it sounds like a machine gun is under the valve cover…