Any help is greatly appreciated:
Recently had misfire on cyl 8. Replaced all spark plugs, moved cyl 8 ignition coil to cyl 3 and drove fine for several hundred miles. Cyl 3 threw a misfire code, and in process of pulling ignition coil to swap with new one the coolant elbow snapped and needed replacing. Replaced coolant elbow and ignition coil and started up, now misfires on multiple cylinders. Continues to move with testing through moving ignition coils and replacing spark plugs. Disconnected and re-seated injectors. Compression test is fine when wet testing cyl 3, otherwise cyl 3 is low by 50psi (no oil dropped in cyl, cold). Continued testing is coming up with just more randomness, now misfires are just on bank 1.
Also posted on audizine (I hope its ok to post links?): https://www.audizine.com/forum/showthread.php/818138-Misfire-spreading-help-with-proper-diagnosis?p=13239790
Full story, bulleted
Trying to diagnose a moving misfire. Have done initial troubleshooting and am at checking injectors with Vag-Com and could use a little help
2 years ago (10K mi) I had a misfire on cylinder 2 - replaced plugs (all looked pretty bad at 10K) and replaced the 1 ignition coil for that cylinder B7 S4 Spark Plugs - 11.16.16
The latest, from when I had a cylinder 8 misfire originally, earlier this month:
- Pulled all spark plugs, replaced with new (10k on these plugs - looked OK but not great: B7 S4 Spark Plugs - 6.07.18)
- Compression test showed cylinder 3 has bad rings - low compression until adding a little oil to cylinder, was fine after oil
- Swapped cylinder 8 (misfiring) ignition coil with cylinder 3 ignition coil
- Ran fine for several hundred miles until last Sunday when I got a bad misfire on cylinder 3
- Began making access to bank 1 to replace cylinder 3 ignition coil and the coolant elbow snapped B7 S4 - Misfire Diagnosis - Coolant Day
- Replaced coolant elbow with aluminum elbow
- Replaced ignition coil on cylinder 3 with new coil
- Added coolant to reservoir and started up. Ran rough as hell, turned off. Cleared codes (showed multiple misfire on first startup, just like when I swapped the new plugs in and moved the ignition coil and started it up first time. After clearing the codes that time, it ran fine with no codes)
- Started up again, rough as hell, showing misfire of cylinder 3 again. New coil, plugs have 300 miles.
- Checked all connections, including injector and nothing looks/feels out of place
- Re-installed the new ignition coil on cylinder 3 just to be sure - started up and still rough.
- Moved new ignition coil from cylinder 3 to cylinder 4 (and vice versa) and started up - misfire spread to now cylinders 3 and 4
- Moved all ignition coils around:
cylinder 1 to cylinder 8
cylinder 2 to cylinder 5
cylinder 3 (new) to cylinder 7
cylinder 4 (original) to cylinder 6
cylinder 5 to cylinder 1
cylinder 6 to cylinder 4
cylinder 7 to cylinder 3
cylinder 8 to cylinder 2
- Misfiring spread again, now misfiring on cylinders 3, 4, and 7
- Swapped cylinder 7 (new ignition coil) back to cylinder 3 (originally misfiring cylinder, suspected bad ignition coil)
- Swapped in new (used but good condition) spark plugs to cylinders 3 and 4
- Cylinder 7 misfire is gone and cylinders 3 and 4 are still misfiring
- Cleared codes, re-ran with logging. Instead of misfires on 3 and 4 like I was expecting, I am now getting faults for misfire on 1, 3, 5, and 6 so it’s no longer isolated to bank 1 and really is jumping around. The current ignition coil in cylinder 5 is new as of 2016, or roughly 10K miles ago.
- Torqued intake manifold bolts, some had a good half turn or more in them. Bolted everything back up, fresh gas (was close to empty when this misfire on cyl 3 happened)
- Reset ECU by disconnecting both battery terminal leads and touching them together via a jumper cable, left battery unplugged overnight to drain capacitors. Cleared engine codes via VagCom. TB reset via VagCom.
Started up right away and with a better idle than before but still misfiring:
Cyl 1 Cyl 2 Cyl 3 Cyl 4 Cyl 5 Cyl 6 Cyl 7 Cyl 8
0 0 4090 195 840 0 518 0
- Swapped ignitions coils: 1/3 and 5/6, cleared ALL DTC codes (had intermittent code issues related to battery drain, I presume - see earlier log above)
Misfire codes came back on cylinders 1, 3, 4 but my misfire count log didn’t save correctly and then the battery and my instant start charger both got a little too weak to keep testing so they’re re-charging (car on Battery Tender Plus)
I’m thinking I need to order injectors to test there but I had read somewhere there is an output test for firing each injector individually. Anyone know what group it is?
I’m also double checking the vacuum line connections best I can, based on these pictures/diagrams: https://www.audizine.com/forum/showt...outing-Diagram