Hi,

I bought an ex police interceptor about a year ago. Owners wife sold it to me, she told me her husband had mentioned a lifter but couldn't recall anymore details.

Cylinder 8 misfired for a very long time, still drove fine, noticeable shaking in the cab and power would cut out intermittently (car would start to decelerate with constant pressure on the pedal and in cruise aswell, pressing harder on the gas would cause it to rev up and continue driving).

I drove the car to school (200 miles) drove it around for the semester and brought it home for the winter for storage.

I decided to pull the head off to see what was going on. After pulling the valve cover off, I noticed the intake push rod on Cylinder 8 was completely bent. I took the head off aswell to see what the cause could be and the snap ring on the lifter had broken off (the bushing wasnt even seated in the lifter). The head still had its cross-hatching fully intact and seemed to be in good shape.

I ordered a new lifter, pushrod, and head gasket and just got it back together today. After firing up the engine, there was noticeable knocking and a popping sound coming from the same side of the engine as cylinder 8. Tried different plugs, swapped coil packs, tested the coil pack plug and injector plug (all working) until I realized I forgot to plug in the MAP sensor.

After plugging in the MAP sensor, it idled well (Still some shaking in the cab but seemingly better)

When I was consistently driving the car I noticed patterns in how it behaved. When idling, decelerating, or holding speed with cruise on flat areas at a moderate speed (below 60mph usually), the check engine light would stay solid. Acceleration caused the check engine light to flash

Taking it for a test drive today I was hoping to see that change, however its still the same.

What I didnt see before was the P3441 engine code. "Cylinder 6 Deactivation/Intake Valve Control Circuit/Open"

At first I assumed the misfire was absent because the MDS had shutoff Cylinder 8 when not necessary, however with that code being present, I'm wondering if theres a problem with the MDS altogether.

Would like to know your thoughts, I'm new to cars so anything is helpful.

Thanks

Edit: Forgot to mention I compression tested the cylinder and its at ~150psi

 

You bought a Ford and are asking about it here?




Cylinder heads don't have cross hatching, did you mean the cylinder itself (I hope)?

MDS doesn't ever do anything with #8, it's ALWAYS 1, 4, 6 & 7. The code you get literally means that circuit is open/not connected; very good possibility a critter got under your intake manifold and chewed wires. They like to get into that pad and nest. Check the wire from #6's MDS solenoid up to the harness before it goes to the PCM.