I have a 1999 dodge ram.The other night out of the blue it started to run rough and check engine light came on.Checked it with scanner and it came up P0305 CYLINDER 5 MISFIRE DETECTED.Any ideas of what this could be? Plugs and wires seem to be ok.
Could be a plugged or dirty injector.
Yep - it's a misfiring cylinder (sorry - had to state the obvious). Could be due to lack of fuel (clogged/non-functioning injector/damaged injector wiring/failed PCM), lack of spark (fouled plug, bad wire, bad distributor cap), or lack of compression (stuck/burnt valve, blown head gasket, cracked head) - just to name a few possibilities.
Quick tests to eliminate problems are: swap plugs and wires #5 to #7 (on both ends - plug end and distributor end). Clear the codes, and run it again. If the misfire moves to #7, you've got either a bad wire or bad plug. Next bleed the pressure from the fuel rail (either through a test port, or pull the fuel pump fuse and run the engine till it quite), then unbolt and pull up the driver's side fuel rail, and swap #5 and #3 (#7's harder to work on) injectors. Put it back together, and see if the misfire moves to #3. If so - bad injector.
Next thing would be to perform a compression test, at least on #5, but I'd do the whole left bank (so you have numbers to compare to - do the other 4 if you're ambitious). If compression is low (
Tom is right, literally could be anything and you could even get misleading successes. I chased a P0307 problem on a 97 RAM 5.2L for over a year. With the help of this group we tried many things and several times thought we had it nailed until the problem came back a few days, weeks, or few months later. Always on the same cylinder and progressively harder to keep it cleared for any length of time. ONE OF MY SYMPTOMS we discovered late in the diagnosing was that once we had the code cleared (just by resetting it with a scan tool) we could keep it cleared by never allowing the engine RPMs to *ever* fall below 800 (i.e., holding your foot lightly on the gas while at a traffic light).
Solving this could be as easy and cheap as rerouting & separating your plug wires to prevent cross-firing; it could be as hard and as expensive as a cracked cylinder head. Cylinder misfire codes can sometimes be really tough to accurately diagnose because as we discovered there are so darn many variables that can cause it. We ended up finally going to a dealer where they did a full top end overhaul, replacing both cylinder heads (complete, all new heads, valves, springs, rockers, plugs, wires, etc). I honestly cannot say with any degree of certainty that the dealer actually "pinpointed" the cause as much as they literally shotgunned the whole top end by replacing literally everything it could possibly be. Only after teardown did it become evident that the #7 intake valve seat was cracked.
H>> up P0305 CYLINDER 5 MISFIRE DETECTED.Any ideas of what this could be?
Changed #5 plug ran good for about 4 miles then started running rough again.
Be sure to clear the code each time, either with a scan tool or by pulling the battery cable for about 30 secs.
Fixed the problem.Plug wire was burnt.Thanks for all the ideas.
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Like I always tell folks..........
never,ever,never,ever................................ start diagnosing from where the last guy stopped, or.....take his word for it that what he checked..... checked good.
(I refer you to yer original post)
~:~ MarshMonster ~takes a toke.....sips his crownroyal~ ~:~
You *REALLY* lucked out! My P0307 ended up costing over $2k after a year-plus of trying just about everything. Just goes to show the wide range of things that can cause a cylinder misfire code.
With your luck you might want to pick up a lottery ticket.
Nah - his was actually pretty typical. With _YOUR_ luck, I'd stay away from ladders, black cats, and anyone hoisting a safe or a piano up to a 10th floor apartment :)
Understood. I had a similar costly experience a number of years ago with a Chevy -AFTER- putting in a brand new (not rebuilt) long block. Worst mistake I EVER made aside from buying the Chevy in the first place. The initial 100K was uneventful but it sucked a valve at 105k. Silly me, rather than sell the bones for scrap I thought the pristine body and never-smoked-in interior was worth dropping a new mill in it. Then the tranny went... then the rear end started howling. Somebody ended up with a P.O.S. '69 Camaro with a whole bunch of brand new parts in it.
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