Simon Kribstock Posted June 7 Report Share Posted June 7 Hi everyone, Parked my the other day, running perfectly fine and strong. Go to start it up the next day and it's misfiring badly at idle, corrects itself for a few seconds, then starts idling badly again - very lean according to lambda gauge. Tried again the next day and the same thing except I drove once the misfiring stopped and it drove fine for the 10 minute test drive. Next day, misfire again but has not corrected - constant misfiring. I checked all the plugs and they looked good all brown but 1&2 were wet with fuel. This lead me to believe it's an ignition issue. Verified the gaps hadn't changed @ .7mm but changed all plugs anyway (NGK BKR6ES-11) - same gap - no change. Tried unplugging the COP igniters (converted to COP a few years ago) on 1&2 while idling and it made no difference. Unplugging 3&4 will kill the engine. Replaced igniters for cylinder 1&2 with same OEM igniters (22433AA602) - no change. Loaded semi-old map - no change. I checked the run times values. Trigger signals 1&2 were good and trigger arming voltage was around 1.0v for both - not sure what they're supposed to be. Wiring appears to be intact. Attached log shows misfiring idle to good idle then back to misfiring. Any ideas? Please help intermittent lean AFR 2024.llg Quote Link to comment Share on other sites More sharing options...
Simon Kribstock Posted June 7 Author Report Share Posted June 7 original log upload failed? intermittent lean AFR 2024.llg Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 8 Report Share Posted June 8 It sounds like a bad connection somewhere. Use the ignition test function to continuously fire that coil (with the engine off) and watch the spark while wiggling the loom and connectors etc. Quote Link to comment Share on other sites More sharing options...
Simon Kribstock Posted June 11 Author Report Share Posted June 11 Thanks for the tip Adam. I can hear the ignition 2 control circuit (spark plugs 3&4) firing but 1&2 are not firing as I suspected. I have power and ground at coils 1&2. With the ignition test function active, the signal voltage fluctuates from 0.1-0.9v on both 1&2 coils. According to the FSM, it should be 3.4 volts max for each ignition control circuit while idling. Does that sound suspicious? I also cleaned the chassis, engine and battery ground connections as a precaution - no improvement. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 11 Report Share Posted June 11 5 hours ago, Simon Kribstock said: With the ignition test function active, the signal voltage fluctuates from 0.1-0.9v on both 1&2 coils. According to the FSM, it should be 3.4 volts max for each ignition control circuit while idling. Does that sound suspicious? The ignition pulse in test mode is only 2ms long so a multimeter will not be fast enough to see it. But the values you report sound about what I would expect. If you have an LED test light that will be fast enough to pick it up. You could possibly compare the voltage to the cyl 3/4 coil but im not sure how relevant that will be. Quote Link to comment Share on other sites More sharing options...
Simon Kribstock Posted June 12 Author Report Share Posted June 12 Solved. Found someone had spliced wires into the ignition signal wires for something auxiliary near the ECU. I guess the resistance slowly grew enough to interrupt the signal. The ignition test mode was key. Sounds like I need to upgrade my incandescent test light though haha Thanks for the help Adam! Quote Link to comment Share on other sites More sharing options...
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