While trouble shooting my daughters '06 Escape 3.0L for MIL and code PO356 (coil F pri/sec circuit, very intermittent split second of eng. roughness) I noticed a light 'clacking' noise from the area of cyl. #6 intake camshaft, seemingly from the area of the last cam bearing, drivers side. This sound was noted after the car was driven down the freeway and was well warmed up. However, after a couple hours I went out to listen again and the clacking sound was gone even though the eng. was still warm, so I drove it a couple blocks and once again with the hood up I could hear the light clacking. Is there any possibilty this could be from a faulty hydraulic lash adjuster or roller rocker on cyl.#6 intake since that's the area the noise is coming from? If so, could a faulty lifter cause an intermittent eng. roughness and the crank & cam sensors are relaying the crank decel to the PCM and it's throwing the PO356 fault code since it doesn't know any better? This would be a little more plausible to me if the PCM was throwing a 'misfire code' instead of the 'coil #6 pri/sec' but thought I"d ask...any ideas?

 

No, *I* don't think so. Even if the lifter was fully collapsed, it would still open the valve enough to run. You may [or not..] remember hearing some of the older cars with leaky lifters that would start up and tap-tap-tap for a minute or so, when you first started them cold, or warmed up when you stopped for a signal light. The lifter could have been collapsed completely and you would have had .060 clearance at the rocker arm tip. The lift was on the order of .25 inch, so it would be difficult for that difference to make an engine idle poorly or have a detectable miss going down the road.
FWIW, I hear a slight noise when my DWW comes home from Meals on Wheels or volunteering at the hospital. The engine is warmed up, and there is a slight noise. I have not investigated yet, but it could be the noise noted on the TSB about front camshaft bearing cap alignment. The leftmost cap on the front exhaust somehow causes a noise. The 'cure' is to loosen all the caps, pry this one cap towards the driver side, apparently keep it there somehow, and tighten all the cam retainer bolts according to sequence and torque spec. I don't even remember which model years where this TSB applies.
They spec such thin oil, it seems to me that any sort of looseness or wear will signal a lot sooner on these engines than older designs which depended on higher viscosity lubes. Just an opinion.
tom

 

Thanks for input Tom,
For what it's worth, I don't think my idea has much merit either. I pulled the front valve cover to take a look and visually all looks well & very clean. I did pull the intake cam left most bearing cap to see how the wear surface and cam looked, like new so nothing there. I'm making a version of the valve spring compresser tool as shown in the service manual so that I can pull the cyl. #6 intake rockers and hydraulic lifters just for grins. I also ordered a couple of the lifters ($13.43 ea.) just to eliminate that possibilty. If the roller rockers look good and I can't find anything else, I'll put it back together and not worry about it.
Tom, don't count on moving those cam bearing caps as they are doweled into the lower half and a snug fit, just so you know. Oh, and I'm running Amsoil 5w-30 full syn. because that's what I run in everything else, this Escape is consistently getting about 23 mpg at 60-70 mph highway so it hasn't hurt the mileage.

 

Just to follow up on this post, the tool worked well and I removed cyl. 6 intake rocker arms and hydraulic valve adjusters. Although all parts looked good and lifter bores were nice, I replaced the two hydr. valve adj. and put it back together. I took the car on a 175 mile freeway trip and am happy to report no more clacking when good and hot.