Engine specifications, spark plugs, timing, and vacuum

Compression test specifications

For M60B40

• 10-11 Bar or 142-156 PSI (6 strokes)
• Maximum difference: 0.5 Bar or 7 PSI

Engine idle specifications

The idle speed should hold steady at 600 RPM with a variation of up to 50 RPM.

Troubleshooting unstable idle

The RPM is not holding steady or the needle is periodically going up and down. like it's taking deep breaths. The symptoms might also improve or disappear in a hotter climate.

• Check the Mass Air Flow sensor (MAF)
• Check and clean your Idle Control Valve (ICV)
• Check the Throttle Position Sensor (TPS)
• Check the intake for pressurized leaks

Engine firing order for M60B40

The bank-1 is on the passenger side and houses cylinders 1 through 4. Bank-2 is the driver side and houses cylinders 5 through 8.

Spark plugs

Compatible spark plugs for M60B40

• BKR6EK
• BKR6EK
• BKR6EQUP

Torque

Spark plug to the engine: 22-23 Nm

Bosch +4 Platinum

There are tons of threads on this subject.  Personally, I have not experienced any issues with these spark plugs but also don't know if I felt a difference. The car takes 8 of these babies – vote with your wallet.

Application chart

How to read a vacuum gauge

This is an interesting test of the overall engine health. I thought the process would be super complicated, but it's just a couple of easily observable conditions. You will need to get a portable vacuum gauge and be able to route it to the manifold.

Taking a measurement

1. Take your BMW for a spin to warm up the engine. Turn the engine off and use a tee to tap a vacuum line. Connect the gauge to the tee
2. Start the engine and take a close look at what the needle in the vacuum gauge will do
3. The ideal reading would be rock steady 17-22 in.Hg (inches of mercury) @ 1000 RPM

Processing the results

Low steady vacuum reading (15-20in.Hg) at idle

This could indicate a problem with an external vacuum leak, late ignition or valve timing, low compression or stuck throttle

Needle fluctuates from 15-20in.Hg rapidly at idle

This could indicate a sticky valve or ignition miss. Weak valve springs might cause fluctuation at higher engine speed

Gauge needle drifts rapidly at idle

Possibly a small intake manifold leak or bad injector O-rings

Gauge needle stays steady then drop regularly to recover and repeat over and over

Gauge needle stays steady then drop regularly to recover and repeat over and over Burnt valve(s) or improper valve adjustment. The needle will drop when the defective valve operates

Gauge needle stays steady then drop to recover and repeat irregularly

Sticking valve causes the needle to drop each time it hangs open. The reading will not drop at regular intervals like for a leaking valve

Gauge needle drops gradually at idle

Chocked muffler or obstruction in the exhaust system. A restricted exhaust (like the cat.) will not allow the engine to exhale properly causing an increase of pressure inside the intake manifold. The result is a lower manifold vacuum

How to verify your engine timing

The primary symptom of timing that is out of specification is a blown engine. Do not accept work and tow the car back to the shop if your engine refuses to hold the idle after a rebuild.

Possible symptoms

• Engine is running rough
• Random O2, lean, or rich condition codes are thrown
• Slow engine response when switching gears

Diagnostic

• Start the car, and lean against the car's fender while the engine is shaking. If your whole body is shaking this is an indication of a non-mount related vibration.
• Connect a vacuum gauge to PCV plate in the rear or brake booster line. If the reading is steady but below 14-16 Hg, your timing is most likely low and is out of specification.

Repair

The repair requires two sets of hands and a special BMW toolkit. The toolkit allows you to lock the flywheel in place, aligns the camshaft, and keeps the chain tensioner in place.

• Follow the torque specifications to a tee
• When spinning the engine, always spin it to the right while facing the front of the car
• Do not forget to remove the flywheel locking pin when attempting to spin the engine, or before starting the car

Please consult the Bentley repair manual if you need a detailed break down of this job.