Cannot diagnose misfire. No codes.
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From: Sindh
Cannot diagnose misfire. No codes.
Hey fellas,
I am experiencing a strange misfiring problem in my 4gr engine. Started up one morning with severe misfiring in every driving condition and idle. No codes. Unplugged every coil one by one and turns out there's a problem in Cylinder 3 and 5 as there is zero response when I unplug these cylinders. The coils were firing so naturally I figured there's an injector problem. Following is my self diagnostic journey in chronological order.
1) replaced injectors- issue remains
2) replaced with another set- issue remains
3) swapped the injectors around- issue remains
4) swapped all coils- issue remains
5) put new plugs twice- issue remains
6) replaced injector driver with loom- issue remains
7) put in complete set of injectors, rails, injector driver with loom, plugs, intake manifold, throttle body, and ecu from a working engine- issue remains
8) did a compression test, 190 on all cylinders
8) pulled the head off, no leaking valves. Still sent to the machinist to check all the valves, seats, guides and polish off all the carbon buildup- issue remains.
Right now I'm at my wit's end. There is pulse to the injectors. There is spark on all the coils. There is good compression on all cylinders. No amount of wiggling the wiring loom makes any difference to the misfire. Looking forward to hearing some pointers from the experts here.
Regards,
I am experiencing a strange misfiring problem in my 4gr engine. Started up one morning with severe misfiring in every driving condition and idle. No codes. Unplugged every coil one by one and turns out there's a problem in Cylinder 3 and 5 as there is zero response when I unplug these cylinders. The coils were firing so naturally I figured there's an injector problem. Following is my self diagnostic journey in chronological order.
1) replaced injectors- issue remains
2) replaced with another set- issue remains
3) swapped the injectors around- issue remains
4) swapped all coils- issue remains
5) put new plugs twice- issue remains
6) replaced injector driver with loom- issue remains
7) put in complete set of injectors, rails, injector driver with loom, plugs, intake manifold, throttle body, and ecu from a working engine- issue remains
8) did a compression test, 190 on all cylinders
8) pulled the head off, no leaking valves. Still sent to the machinist to check all the valves, seats, guides and polish off all the carbon buildup- issue remains.
Right now I'm at my wit's end. There is pulse to the injectors. There is spark on all the coils. There is good compression on all cylinders. No amount of wiggling the wiring loom makes any difference to the misfire. Looking forward to hearing some pointers from the experts here.
Regards,
I'd pull the ECU and open the cover. Verify the electrolytic capacitors are not leaking / exploded. You can google that for an image.
If bad you can replace them. Order from digikey and desolder/solder them in. It is known problem on aged Toyota's / Lexus vehicles.
After that you need to ohm connections from coils and injectors back to the driver and ECU...
Hell of a journey. Good luck.
Search lexus ecu leaking capacitor
If bad you can replace them. Order from digikey and desolder/solder them in. It is known problem on aged Toyota's / Lexus vehicles.
After that you need to ohm connections from coils and injectors back to the driver and ECU...
Hell of a journey. Good luck.
Search lexus ecu leaking capacitor
What all have you done and do you have a link to it?
I'd start by ohming wires. Injector to driver. Driver to ecu. And inspect ecu caps as noted above.
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