clackity clack, missing

96XJ, 4.0, 242, 220,000 miles.

So I'm hoping for the best, but we'll see.

Yesterday I dropped the hammer passing a couple of slow movers on the way to work (late, of course) and ever since I have a 4.0 that is missing badly at idle / sounding rough with some clackity clack audible from the valve cover area (at least I think it's coming from the top end.)

Getting 300 and 301 codes to go with the 138 that I have had for a long time with the disconnected post cat O2 (running a pipe until I get some extra cash.)

Still seems OK and plenty powerful while driving, oil and coolant both look normal. Plugs look OK when I pull them. I have a compression tester/fuel pressure tester/multimeter/etc to start checking things out.

I don't have time to get into until Sunday but this is my DD. Safe to keep driving for a few days you think?

Most likely prognosis ideas?

Also noticed today - oil pressure is bouncing around between 3/4 and max line on the gauge. It always read fairly high, but not with the fluctuation until yesterday.

Some times this sound is oil not getting to the lifters. My sister did it to her old. Ford often enough, add a couple quarts and it go away no idea how that car survived her. My concern would be the oil pump is going or some gunk came lose under the high oil pressure of passing and is clogging it some where. Could be the motor giving out too, but I'd set it aside if you can , if something mechanical is failing it could leave you stranded.

Change the oil filter immediately, and do not use FRAM oil filter. How old is the oil, which oil?

Check the spark plugs on all six cylinders for signs of distress (oil, coolant, water....), and the oil and coolant for cross contamination right away.

Cap, rotor bad?

Bad primary spark plug wire?

Cat Converter may be damaged and blocking exhaust flow due to O2 sensor being disabled (or bad), and running the engine rich, whcih burns up, overheats the Cat converter.

Like EcoMike said, change the filter and check the oil level. If that does not fix it, I would do a compression check before spending a bunch of money on parts.

No cat

Oil level looks good but I will do a filter and oil change

Using Rotella-T 15_40 (still have a case of the old stock from before they changed the standards)

Mobil 1 filter

Plugs,wires, cap less than a year - rotor 6 months (took that long for Rockauto to send the right part after sending the wrong rotor first time around)

Swapped plugs tonight - no change.

No oil or coolant contamination.

I will test compression on Sunday - no fear of me spending a ton of money on parts before diagnostics. If I had spare change I would spend it on food or heat first.

Adding a quart of Rislone along with 5 qts of the new oil change could help clean the lifters. My 87 with 264k gets a qt of Rislone every other change & it keeps her happy.