I have no experience with freeze frame data, but FYI, my 97 (4.2) was setting PO171( system adaptive fuel too lean - bank 1), PO174 (system adaptive fuel too lean, bank 2) and PO305 (misfire cyl 5) which I thought might be IMRCs at the back of the lower
intake manifold at first...but listening to the advice here at FTE saying it is normally indicative of a vacuum leak, I tracked down two leaks by applying vacuum to all the small vacuum lines in the
engine compartment - the
brake vacuum nipple was holed/broken and a small vacuum line behind the battery tray (red line (EVAP?) plastic hose joiner at elbow was cracked). I couldn't believe that small amount of loss vacuum could set 3 codes continuously but it did (engine was indicating 19 inches of vacuum throughout the problem. (Fixing the vacuum leaks made all the codes go away - fingers crossed they stay away).
Previously, I had checked my Electronic Vacuum Regulator & it was within specs, & I had changed my differential pressure feedback sensor (DPFE). I checked both
Intake Manifold Runner Control ( IMRC) while I had the lower intake manifold off and cleaned the EGR passages as well . Rubber elbow at at RH end of plenum was also replaced as well as new hose around PCV valve area.
To eliminate #5 spark plug as a problem, I switched it with #6 to see if the problem moved.
Hope this helps
Flags