Hello, hopefully somebody with a similar issue can chime in or offer some advice on how to further proceed. I'm working on a 2012 Ford Mustang 5.0L V8 and I'm experiencing a P0024 (exhaust camshaft position timing over advanced bank 2). I went through the basic diagnosis tree per Ford and was led to replace the camshaft VVT phaser assembly.

- Oil pressure hot was 10-12psi idle hot (spec is 10-15psig idle hot). - VVT monitor bank 2 exhaust phaser stuck at or close to zero degrees. - Under WOT, phaser would advance full to around 40 degrees and be steady until reduced throttle. - Phaser is not variable like the others are, computer is commanding it proper. - Engine is very quiet, no noise or abnormal chatter.

Fast forward to today, when pulling apart the engine I noticed a few things. The oil pump is an aftermarket Melling pump (standard) and I didn't see any markings on the timing components other then the 4 camshaft phasers. The phasers are OEM but not sure about the chains, guides or tensioners. I replaced the bank 2 VVT phaser with Ford OEM as well as the filter behind the camshaft. Also removed the oil pump to verify clearances and replaced the pickup o-ring.

NOTE: When compressing the secondary tensioner by hand to pull the phasers forward and the chain off the tensioner guide, it wouldn't compress. Lots of pressure on the chain. It took a heavy amount of pressure by hand until it became free. Bank 1 didn't have this issue. After compressing the tensioner numerous times, it didn't appear to be an issue.

When I had the timing components removed, I blew shop air through the large opening in the camshafts where the filters are located. It did not blow easily. Seemed to be a fair amount of resistance. Not sure what is normal however since I didn't remove the phasers and try the same on the other bank. Also from my understanding, the first generation coyote engines have oil restrictors built into the cylinder head gaskets.

Finished up bolting everything together and went for a test drive. Phaser operation seemed to be back to normal. It was variable and obtaining the desired position. I did 2 WOT runs and that's when the problem came back. PCM threw code P0024 once again and phaser operation is no longer variable and going to desired position per PID.

I'm leaning toward an oil restriction somewhere in the engine but I really am not sure. Also not sure if I blew shop air through the correct area to hopefully blow any gunk out of the passages. Engine oil upon arrival was very clean. I added .5 quart ATF and it still was clean when I drained it. No buildup under the valve covers. I believe the secondary tensioner is oil pressure controlled as well, but not sure why it was stuck. My thoughts are oil pressure built up in the head past the restriction and caused it to not relieve pressure. Pressure must be bleeding off though since the exhaust phaser will go back to zero degrees.

Not sure where to start. Thought about doing an engine flush but I don't believe this will necessary make any difference. I could always tear down the engine but I'm not sure if I could find what would be causing a restriction. Maybe there isn't even a oil restriction, but I'm exhausting my ideas.

Any help is appreciated.

Brandon Sheffield
Owner
Beresford Automotive LLC
Beresford, South Dakota, USA