I've read for the last year or two about some consumers having sludging problems; I recently found the answer for one of my friends with a 1998 Toyota 3.4L Tacoma - he didn't think changing his PCV valve was really that important. We helped him in getting his oil analyzed and found the oil to be two grades out of spec; far from sludge but on it's way (from a 30W weight to a 50W ) at 100 degrees C. We changed the PCV valve, changed the oil / filter and will resample at next interval; that will be a while so stay tuned.

'Rider Support'
(C.)918-636-1281

Didn't think that the 3.4 Tacoma's were supposed to be sludge prone, or at least notorious for it?

What oil/filter is he using? I'd be tempted to run a syn oil if I had sluging issues!

Might consider a mild engine cleaner?