[cyruscat]

Persistent engine misfire growing worse until hard miss and cannot drive.
Car specs:
2007 Z4/E85/N52
101,000 miles

Already replaced parts:
O2 sensors
Vanos
Plugs with recommended NGK
Coils
MAF and MAP
Air filter
Oil and filter
Injector cleaner in gas, Technor couple tanks in row.

Basic engine operation requires air, ignition, fuel, compression, timing of all.

1. Test for air/vacuum leaks
A: Removed air intake pipe between MAF and throttle body. sealed one end and did smoke test under light pressure
RESULTS: No leak

B: Removed and cleaned throttle body, sealed opening of intake manifold and did smoke test under light pressure. Input thru CCV hose end.
RESULTS: No leak
Conclusion: Not source of problem

2. Ignition test for all cylinders/coils/plugs firing
A: Engine running I unplugged one coil wire at a time while monitoring engine idle.
RESULTS: Cylinders 1 - 5 gave little change in idle. Cyl. 6 gave major change with engine almost dying.
Conclusion: Cyl. 1 - 5 are very week. Cyl. 6 firing strong

B: Pulled one plug at time and reinserted in coil. grounded plug while assistant cranked engine and I monitored cylinder for compression stroke.
Results: All cylinders fired hot at same time it hit compression top dead center.
Conclusion: All Cyl. receiving hot ignition at top dead center of compression stroke.

3. Fuel test delivery
A: With engine running used infrared thermometer and measured temp. of each exhaust runner. Common exhaust temp. on warm engine will be 500-600F at head exit.
RESULTS: Cyl. 1 - 5 had low temps 350 - 447F. Cyl. 6 had 567F
Conclusion: Cyl. 1 - 5 not receiving enough fuel to run normal. Cyl. 6 in expected range.

B: Check fuel injectors for good wiring connections
RESULTS: all connectors missing spring locking clip. Someone has been here before and did poor job.

C: Cleaned and seated connectors firmly
RESULTS: No change in performance

D: Using mechanics stethoscope listened to each injector with engine running. Good injector will sound off with positive, firm click when it triggers.
RESULTS: Cyl. 1 - 5 have weal erratic rattle sound. Cyl 6 has loud positive Click.

Conclusion: Injectors 1 - 5 suspect. Next step is to use NOID tester on wiring harness to each injector to check firing pulse.

More to come............