Some requisite background on the problem:
Back in '09 I picked up a beat-to-hell ranger for $700 on craigslist. 44 miles later I ended up having to rebuild the engine (my first rebuild ever). It all came together except for a few minor things (2 CEL codes: p0135 & p0141) that were there before the rebuild. Almost 1 year after getting it up and running the new problem started.
Sudden power loss
The engine sounding ‘bogged’
But they all seem to come and go. Sometimes it will idle fine, others I have to really work to keep things going. The problems with power loss and backfiring (and rough idling) seem to get worse/more common the longer the truck has run. Usually after a backfiring (or five) power returns for a little bit and then bogs out again.
-Things I’ve tried-
-Fuel pressure checks out between 25# and 35#s at idle/coasting, 40#s under WOT (Video of test run: http://www.youtube.com/watch?v=uzxkCnUuy_4)
-No gas smell in pressure regulator’s vacuum line (line is not plugged either).
-I have not been able to locate any vacuum leaks (aerosol spray test).
-I have installed a new fuel filter.
-Plug wires are routed correct.
-Plugs and wires are new, gapped correctly.
-MAF has been cleaned recently.
-IAC valve has been cleaned several times.
-Mechanical timing has been checked and re-checked
-Swapped coilpacks to test if I had a bad one
So here is my limerickal next guess:
A problem most vexing,
No new codes have been logged;
My next shot in the dark is,
That the cat may be clogged.
My thoughts are that the cat is partially clogged and, once it heats up, it swells closed and begins to build up exhaust pressure. The backfirings temporarily knock the clogs free and return the exhaust to a free-flowing state. Any thoughts?
And a parting shot in the form of another limerick:
This truck’s an enigma
What’s even left now to break?
I think it may be better,
at the bottom of a lake.