Well here we go.... as I mentioned in my introduction, I have extensive experience with my91' 2.3 (8-spark plug) Ranger. 399,500 miles.
High mileage, little power at high RPM, hardly any pickup above 80MPH, you just floor the accelerator and wait. Driving this kinda makes one very cognizant of conserving speed and momentum when driving. So, I figured my engine was just tired and needed a rebuild so...I bought a 2006 diesel VW Beetle and let the Ranger sit and drove it sparingly.
One fine day I get a wild hair and check the compression on the Ranger. Well to my surprise 180pounds per cylinder with very little variance. The engine definitely lost its perk but compression doesn't seem to be the problem. I did however, let the engine spin over 7 or 8 times to get compression to that level. I'm told by a mechanic that it is acceptable to do. I'm still not sure. An engine that gives good pressure after one or two revolutions is certainly better. Anyway, 175-185PSi was the Range.
I've changed pretty much everything (engine related) electrically save this little flat white electonic gismo mounted to the intack manifold. I was told by a Ford mechanic not to change it. And...I've never replaced the computer.
The engine at times, quite frequently, runs very very rough, mostly when idling (it never kills out). It clears up in less than a minute after driving, but the engine never approaches the power it once had or should have. Once in a while it would have some pep to it and I would notice a change but that was short lived. This hasn't happened in a long time. Mechanical engine issues (clearance, valve, pistions, camshafts) don't fix themselves, they just get worse.
Due to the age of the vehicle, I am reluctant to spend allot of money to solve this problem but hey, I'm attached to the old girl, who mostly finds duty in short runs to the store and helping around the yard.
I've never found the PCV valve on this truck in 18 years. I've looked repeatedly. I've never had the valve cover off, it hits the firewall when I try to remove it but I've only tried once about 15 years ago.
I've always done good PM on the engine. The truck starts right up, idles fine, revvs good...what can I say ?
Oops. Forgot to mention. The missing and rough running is accompinied by wild variations in the tach, not representative of engine RPM