1999 ram 1500 4x4 has been getting this cylinder 2 misfire for over 2 years
now. It has went away a couple times for a brief period (less than 2 weeks
each time) but coems back. After I ran 2 cans of cc cleaner and changing the
plugs the code was back in minutes. I cleared all codes out after the
cleaner and got about 5 miles before it came back. I have replaced the
following: cap, rotor, wires, plugs and injector. I did the tsb about
rerouting the wires as well. I am at a loss now.
Where is the sensor for this and could it be defective?
What about the fuel rail?
What exactly causes this code to trip?
I have 65k miles on the engine so I doubted it was buildup but worth a try.
Have you happened to notice if the misfire event occurs more at low engine
idle (below 1000 rpm) than above? We didn't realize that with my P0307
misfire problem until we got it in the shop and had it idling in gear with
some test equip hooked up.
Once we realized that I found I could actually prevent it from happening
just by holding a slight throttle pressure whenever coming to a stop.
Never let it drop below 900~1000 rpm and the misfire code would never
occur. But sit there at 5~600 rpm at a light w/your foot on the brake and
the misfire code would happen almost every time. Always the same cylinder
In the shop idling in gear we could see multiple misfires counting up,
typically about 8 per minute, all on cyl #7. That was actually an exciting
revelation as it was the first time we finally figured out it was only
happening at very low engine rpm, i.e., when decelerating from about 30
mph down to a complete stop, and/or idling in gear. We thought of simply
turning up the idle speed, but that would only mask the problem and not
fix it, plus then the truck would idle at about 1500 rpm in neutral.
The CC cleaner (1st application) to a hot engine then waiting about 4 hrs
before revving the SH#! out of it and taking it out on the tollway for
several WOT upshifts made a noticeable improvement tho the problem would
still sometimes reoccur (but far less frequently). The second application
of CC cleaner (again to a hot engine) and then letting it sit 12 hours
(overnight) before revving the sh%! out of it and another 20 mile trip of
multiple pedal to the floor upshifts and the problem has so far (3 weeks
now) not come back.
I'm not fully convinced it's 100% fixed, but I'm optimistic that we're
onto something here.
I honestly doubt that it's "fixed" just that the symptoms have temporarily
cleared up following two doses of CC cleaner.
Prior to this we had tried everything, starting with a compression test,
replacing the wires, plugs, coil, MAC valve, flushing injectors, swapping
injectors, the wiring TSB, etc.
Initially (18 months ago) the problems cleared up for 5-6 months ar a time
just with an injector flush, but over time came back (always same
cylinder, P0307). Most recently the injector flush was no longer having
any effect. Also it wasn't until 6 weeks ago that we woke up to the fact
it was only occurring at low engine speed (below 1000 rpm).
The CC cleaner I feel has us at least back to where we were 18 months ago
with the problem being temporarily mitigated. I'm hopeful it's gone
forever, but we fought it so long and hard that I'm not optimistic.
It won't show up on a leak-down test, but anything that's hanging up a valve
will show a lower-than-normal compression. If it's intermittently sticking,
well, then yeah - you're shooting blind... but any kind of diagnosis in
this case is incomplete without at least a compression check.
Now this would depend on how bad the valve was sticking now, wouldn't it.
And also would not normally cause a misfire so what exactly is your point?
Worn guides also normally cause smoke before they get bad enough to cause
And that will also not cause a misfire so again, what is your point?
As Tom said, a compression check is also a required test to formulate a
valid diagnostic. The valve could be carbon locked which WOULD show on a
compression test and for all we know, there could be carbon buildup causing
excessive compression that could be causing the spark to be "blown out"
indicating a possible weak coil. I would also put the vehicle on a scope to
check both the ignition and the injectors for proper operation. Just
because the injector has been replaced doesn't mean that it is functioning.
If at first you don't succeed, you're not cut out for skydiving
T-Bone. The missfire is apparently very intermittent, and not felt -
from what I gathered. A loose valve guide WILL cause intermittent
missfire - enough for OBD2 to pick up. A functioning catalytic
converter will clean up the oil smoke from one bad guide without much
problem. A sticky valve - if not real bad, will also cause an
As for a bad lifter - it CAN cause a misfire, depending on the mode of
failure. If a lifter sporadically pumps up it CAN hold a valve open
enough to cause a misfire every once in a while.
And yes, there are many things a compression test WOULD find - but
just because the compression test reads OK does NOT mean there are no
valve or valve-train related issues.
I've seen ALL of the above cause misfires
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