4lo, CEL,traction, misfire cylinder 7, engine stumbling random

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Pretty much. Incorrect mechanics guesses. Hard to diagnose, seemingly random issue. I don’t know if I’m going to do anything about it since they did put in new head gaskets, machined heads, valves (seats and oil seals, valley gaskets. Valve gaskets, spark plugs, etc…EGR). Still deciding.
 
David Rodgers said:
Pretty much. Incorrect mechanics guesses. Hard to diagnose, seemingly random issue. I don’t know if I’m going to do anything about it since they did put in new head gaskets, machined heads, valves (seats and oil seals, valley gaskets. Valve gaskets, spark plugs, etc…EGR). Still deciding.
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If you paid close to $10K for that work, it may be worth going back to the installer and seeing what they are willing to do as it was their recommendation for you do to do the work, and their recommendation was wrong. And, if they are not willing to play ball, often times you can have a lawyer write a demand letter for a few hundred dollars. It's not a tiny sum of money, so if you are able to recover at least some of it, it may be worthwhile.

Who knows, maybe they'd be at least willing to refund the labor. I'd consider that a success.
 
Same issue with mine. 2019 with 68k miles. I replaced the plugs, coils, and EGR. Either I have a blown head gasket or the wiring/ECM is shot. I'm going to test the coolant for combustion gases before I borescope it, but I'm not happy.
 
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ElRey said:
Same issue with mine. 2019 with 68k miles. I replaced the plugs, coils, and EGR. Either I have a blown head gasket or the wiring/ECM is shot. I'm going to test the coolant for combustion gases before I borescope it, but I'm not happy.
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Are you seeing any pink crud around your engine or white smoke out the back/
 
r2m said:
Are you seeing any pink crud around your engine or white smoke out the back/
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No pink stuff. I just spent an hour looking all over for signs of a leak. I used the combustion gas test kit, too. So no blown head gasket (whew!), but no solution to the problem. The only thing I haven't tried is testing the wiring harness, but I don't have a wiring diagram to work from. I don't get misfires until the engine warms up. If I keep the RPMs under 1250, I don't get misfires.

The issue popped up last year while on a road trip during the first 30 miles. I replaced the #7 plug and coil and the problem went away for about 200 miles. It started sputtering and missing, so I assumed I got a tank of bad gas. I pulled over to refuel and added injector cleaner. Within 20 miles, the sputtering stopped and I finished the last 200 miles. I took it to the Toyota dealership shop the next day (the 2 closest Lexus shops couldn't fit me in). They replaced all of the plugs, coils, and cleaned the fuel system. Since then, I have added a bottle of injector cleaner every two or three fill-ups.

The misfires stopped until last week. I replaced the EGR valve and cleaned the pipes attached to it. The pipes and EGR were nasty. Unfortunately, the problem isn't fixed. I have been throwing parts and accelerated maintenance at the problem for almost a year now. Now I need a trouble-shooting flow-chart or some help figuring out the next steps.
 
My head gasket woes masked as other issues for over a year, including random misfires i thought were from cheap gas.

Are your O2 sensors ok?
 
ElRey said:
No pink stuff. I just spent an hour looking all over for signs of a leak. I used the combustion gas test kit, too. So no blown head gasket (whew!), but no solution to the problem. The only thing I haven't tried is testing the wiring harness, but I don't have a wiring diagram to work from. I don't get misfires until the engine warms up. If I keep the RPMs under 1250, I don't get misfires.

The issue popped up last year while on a road trip during the first 30 miles. I replaced the #7 plug and coil and the problem went away for about 200 miles. It started sputtering and missing, so I assumed I got a tank of bad gas. I pulled over to refuel and added injector cleaner. Within 20 miles, the sputtering stopped and I finished the last 200 miles. I took it to the Toyota dealership shop the next day (the 2 closest Lexus shops couldn't fit me in). They replaced all of the plugs, coils, and cleaned the fuel system. Since then, I have added a bottle of injector cleaner every two or three fill-ups.

The misfires stopped until last week. I replaced the EGR valve and cleaned the pipes attached to it. The pipes and EGR were nasty. Unfortunately, the problem isn't fixed. I have been throwing parts and accelerated maintenance at the problem for almost a year now. Now I need a trouble-shooting flow-chart or some help figuring out the next steps.
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For wiring diagrams, check here at the second post: GX 460 Manuals
I also believe there may be more in that sticky thread that may be of use.
Good luck! 🤞 :cheers:
 
Hiluxforever said:
My head gasket woes masked as other issues for over a year, including random misfires i thought were from cheap gas.

Are your O2 sensors ok?
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Yeah. They were okay. I was doing a better visual inspection and I found the issue. Damn rodent chewed on the #7 injector wire. When the engine revs, it arcs to the nearby metal and triggers the misfire by running too lean.
 
r2m said:
For wiring diagrams, check here at the second post: GX 460 Manuals
I also believe there may be more in that sticky thread that may be of use.
Good luck! 🤞 :cheers:
Click to expand...
Thanks. I was tracing wires when I found the problem. Doing a visual inspection and I found the issue. Damn rodent chewed on the #7 injector wire. When the engine revs, it arcs to the nearby metal and triggers the misfire by running too lean. Now I need to repair the wiring. Putting my old aviation electrical knowledge back into use. Cheers!
1774649096812.webp
 
ElRey said:
Yeah. They were okay. I was doing a better visual inspection and I found the issue. Damn rodent chewed on the #7 injector wire. When the engine revs, it arcs to the nearby metal and triggers the misfire by running too lean.
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Good catch! Thats an odd one.
 
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