srob

So I've continued driving it trying to find anything that would help me narrow down the problem before having to drop it off at the dealer. The other day while sitting at a red light I let off on the brake pedal and noticed a squeaking noise. I thought nothing of it and put some silicone spray up where the pedal moves. Figured a bushing or something just needed to be lubed up. No change to the noise. I finally parked it and did some more digging and found that the master cylinder is leaking into the brake booster and the brake booster is making the noise. I removed the vacuum line to the brake booster, capped it and started the truck, no rough idle! I'm assuming the fluid has leaked in and has damaged the diaphragm inside the brake booster. Thats where my noise is coming from and apparently the vacuum leak causing the misfires.

I have a master cylinder, brake fluid, and a brake booster on the way. I sure hope that fixes it. I'll update once I get it all done.

SteMar

I have the exact same issue it sounds like. I did the typical suggestions also, MC Plugs, 8 Cops, TB and Maf clean, air and fuel filters. Still has that minor misfire at idle. It's worse in park and when I rev it in park, you can really feel the shudder around 1,700RPM then it clears up. I have a very trusted mechanic go over it today. They couldn't find anything and without a CEL, there's no telling which cylinder is misfiring. I'm very interested in what you've stumbled upon. How exactly do you cap the vac line to the brake booster? I'm willing to try anything at this point. Mines an 07 5.4.

srob

Finally got the master cylinder and brake booster swapped out. There was a TON of brake fluid in the brake booster when I removed it. Bled the brakes and replaced the brake light switch (I apparently was a little rough when I removed it...). DEFINITELY made the rough idle better. It still comes and goes from the small amount of driving I've done since the change (less than 50 miles). I'm wondering if the brake fluid just needs to be flushed out of the vacuum system. I could tell when removing the vacuum line from the brake booster that there was some fluid in the line. I'll be driving a good bit this weekend so we'll see after I put some miles on it if it goes away completely. If not I may put some seafoam in the vacuum lines and hopefully that'll get rid of it.

srob

I'd definitely check the vacuum lines. Thats how I found my problem. Shop told me 5 & 6 were misfiring but all in all there was nothing wrong with 5 & 6, the vacuum leak was causing the misfires.

SteMar

I finally took my truck into Ford and they ran diagnostics on the motor. They found the Cam Phasers were shot. Took it to another mechanic and they ran their own test, also said the phasers were shot and that I need a new motor. $7,200 at Ford. I took the truck straight to Carmax and sold it. The damage was already done by the bad cam phasers, so the only long term option is a motor replacement. Bummed to see her go, only had her for a month. It didn't make the super loud diesel ticking, but idled rough and felt like bad misfires throughout the rev range.

Martian

I kinda doubt the engine was shot because it was still running... I think it probably just jumped time... I would've pulled the spark plugs and looked into the cylinders with a camera. Too late though

Christiancito

How much did you get for your truck at Carmax man? I'm thinking about doing the same thing