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Hi all. Long time lurker - first time poster. I have a 2013 EB FX4 SCREW. Other than drop in air filter, catch can, and MPT tunes, it is stock. 61k miles. Has been tuned since new. So over the last year fuel economy dropped...especially when towing and hot idle has been getting a bad shudder. Additionally, it has a horrible rotten egg smell at startup. I tried the stock tune and same issues plus the worst off idle lag I've ever experienced. I changed plugs and no difference. No CEL's. Don't see any vacuum leaks. It seemed like a possible dirty injector, so I put in a little over 2oz/gal of seafoam in the tank. I also performed a KAM reset. So far the rotten egg smell and shudder are gone for now, but I've only driven it about 60 miles since. Jury is still out on any fuel economy changes. If it comes back, I'm thinking of replacing my power brake vacuum pump since my truck's engine build date is within the range for that TSB. I see no issues around braking, so I'm wondering exactly what is defective with the pump? Does it cause so much drag that the hydraulically advanced camshaft actually retards from where the ECU is commanding it to be? Just curious what the pump is doing wrong to create an idle shudder issue since it is just a cam driven pump.

Thanks!
 

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Rotten egg smell is a definite CAT issue. I know this doesn't answer your questions, but you may consider looking elsewhere for your problem. My understanding is the pump is simply there to generate vacuum at idle so your brakes work. Without the pump, and the brake pedal goes to the floor.
 
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The Cats are not necessarily bad. Unburnt fuel getting into them due to a bad injector or rich condition will cause the smell and of course ruin them over time if it is not dealt with. What's good is that either the KAM reset I did or running the injector cleaner has resolved that issue. Hopefully all my issues. I understand how the pump works. Just trying to wrap my head around how it causes the camshaft that it is running off of to retard.
 

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Just noticed that you have a 2013. It's different for your year than my 2012 is. Good to hear you flushed the demons out! That's always a win in my book.
 
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