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Discussion Starter · #1 ·
Hello all,

I have recently begun to experience an issue with an 09 fx35 awd. I noticed my idle would drop rpms at a stand still, almost to the point where the engine would die. I took it upon myself to change the spark plugs and coil packs. I have changed the plugs two times with two different brands (autolite iridium and champion iridium). Each time, the vehicle seems to run fine for a month (although I felt it was jerky when accelerating and cruising at 40 mph, but this was very slight). After a month, the car idles rough, develops a misfire, and flashes a service engine light. After shutting down and restarting, the car runs fine for another 10 mins, then back to symptoms listed above. Before I go down the rabbit hole, I want to see if anyone has had this experience.

I read the vq35hr is finicky with plugs and that platinum should be used, not iridium. Could that be my issue? Or am I looking at something like a vacuum leak or fuel issue? I had the car in last week, they could not replicate the misfire and it had no stored codes. Fuel trims looked good as well. Any help would be GREATLY appreciated.

Thanks all!
 

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Hello all,

I have recently begun to experience an issue with an 09 fx35 awd. I noticed my idle would drop rpms at a stand still, almost to the point where the engine would die. I took it upon myself to change the spark plugs and coil packs. I have changed the plugs two times with two different brands (autolite iridium and champion iridium). Each time, the vehicle seems to run fine for a month (although I felt it was jerky when accelerating and cruising at 40 mph, but this was very slight). After a month, the car idles rough, develops a misfire, and flashes a service engine light. After shutting down and restarting, the car runs fine for another 10 mins, then back to symptoms listed above. Before I go down the rabbit hole, I want to see if anyone has had this experience.

I read the vq35hr is finicky with plugs and that platinum should be used, not iridium. Could that be my issue? Or am I looking at something like a vacuum leak or fuel issue? I had the car in last week, they could not replicate the misfire and it had no stored codes. Fuel trims looked good as well. Any help would be GREATLY appreciated.

Thanks all!
I'm having same issue with my 05 Fx35 but yet to resolve it. Its really giving me concern
 

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Discussion Starter · #3 ·
I'm having same issue with my 05 Fx35 but yet to resolve it. Its really giving me concern
So I have something that could help you. I went in and retouqued my plugs, reseated the coils, pulled off the plenum and cleaned ports, took throttle bodies out and gave them a FULL clean, tightened everything up and it seems a little better. I forgot to mention I had a popping on deceleration (not a misfire but if you had a badass 5.0 jag). Whatever I did fixed the popping which was probably a lean condition due to cleaning tbs and not relearning. I also performed the relearn procedure. I'd start with checking throttle body and related gaskets. If you haven't cleaned them well do that. Don't worry about the reset procedure, it's easy and works everytime unlike some people say.
 

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Discussion Starter · #6 ·
I have. There are no check engine lights and no pending codes that I can see. I am still driving it hoping it will throw a code. Nothing yet. On startups recently, it has begun to have a misfire and rough idle for about 5 seconds but then clears it self up. I am beginning to think somehow my plugs are fouling out quickly. The last set I pulled out were dry and didn't have any weird burn patterns or colors. No oil in plug tubes, just replaced the valve covers. I'm at a loss as of now!
 
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