97 Ram CC/SLT 5.2L 80,800 miles. Compression check was only on a cold
engine and showed no probs, all cyls 130 psi or better, cyl 7 was not the
highest but was among the higher ones. The dealer (sublet) replaced the
CAT and an upstream O2 sensor at approx 65,000.
The problem seems limited to occurring only at very low RPM, below 1000,
as in when decelerating to a stop and/or sitting idling at a traffic
light. Hold your foot on the accelerator pedal to hold idle at or above
1000 and the P0307 won't occur. Engine is up to normal op temp when the
event occurs. Doesn't happen immediately at low idle, but will occur
sometime within the first minute of an extended idle period. Happens
idling in gear as well as idling in neutral or park. 52 psi fuel pressure.
The problem has been ongoing for 18-20 months, but initially we didn't
realize it was happening only during decel or at low rpm. Also at first
flushing the injectors would provide some extended relief, usually several
months at a time. We replaced the coil, plugs, wires, rotor, IAC, did TSB
18-48-98 and now the CC cleaner. Unrelated, also replaced battery and air
Even now whenever the code is cleared the truck runs like a scalded dog,
no drivability issues at all, excellent power, smooth shifting and no
surging. With P0307 stored it is slightly rough idle and some minor
noticeable loss of power.
Ok, the compression check was done on a cold engine and it was ok. This will
be a bitch but warm the engine up good and retest #7 compression. Compare
the warm reading to the cold reading and see if they are still in the same
range. I got this sneaky feeling a valve is sticking sometimes.
Rotsa ruck w/Rita! After things settle down, try one more CC treatment. If
you had a LOT of carbon, one treatment may not have been enough... don't
spend any more $$ until you try this or do the injector swap as Denny
We dodged a big bullet w/Rita. There's still very limited availability of
gasoline right now (2:30 PM Sunday) but the major highways coming into the
city are all clear. We're hearing reports of major traffic jams along
some of the smaller connecting routes that feed into I-10 and I-45. The
trick to use the little back roads was a great idea to bypass the
bottlenecks and get out of town, but coming back in all the major freeways
are wide open and it's the little two lane roads that are jammed up.
Well no guarantees, but it sure seemed to help my old 97 318 (80k miles).
Spray in the full can with the HOT engine idling. It will load up and try
to stall out, just give it enough throttle to keep it running until you
get the whole can into it then shut 'er off and let it soak. The longer
the better, minimum 2 hours, someone here recommended overnight. If you
can, clear any codes before cranking it again (idea being for it to be
running on all cyls) Then crank it up and rev the piss out of it till the
smoke clears then take it for a drive somewhere where you can do several
(8~10) wide-open-throttle (WOT) upshifts, i.e., 5000 RPM redline upshifts.
I went over to the new Westpark Tollway and blasted off a few times
(eastbound at 7:30 PM there was no traffic and more importantly, no cops.)
Turned around at the Beltway and repeated it a couple more times
Westbound. Still too much Westbound traffic at 7:30p to get any more than
a couple in.
I repeated the CC cleaner routine again last weekend. While the first dose
improved things, the second treatment -seems- to have solved it. This time
I also let it sit overnight before cranking it up again. No more P0307 at
all in a whole week of in-town driving. For grins I also poured 20 ounces
of Techron in the tank.
Bottom line is "thanks for the suggestion" - Gee, if only I'd done this 18
months ago ;-)
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