after putting in all plugs and wires and 2 coil packs on cylinders 4 and 8 and replacing both front o2 sensors still has a midrange misfire at 45 mph also noticed injecter pulse values for #2 and #4 drop 2.0 mv at the time the mis starts any help would be appreciated oh yeah this is a 2004 1500 5.7l hemi
Country: United StatesMake: DodgeModel: RAM 1500 4x4Year: 2004Engine: 5.7l
plugs, wires ,2 coil packs #4 and #8 replaced both front 02 senors
Can you feel this misfire? Or is it something that can mostly be seen on the Misfire Monitor using your scan tool?Hi, my name is XX XXX welcome to JustAnswer!.
yes very noticable i am using a mac mentor scanner
Thanks. How heavy of a load do you have on the engine at the time?Is it light throttle (steady speed) or hard throttle and still accelerating? Is it a top-gear only misfire? Or something you feel as the truck goes through the gears?
no load in or on truck normal acceleration just after hitting top gear at steady speed in hard throttle it seams to smooth out have only noticed in top gear
Does your scanner show a particular cylinder that's affected by misfire? Is it the same #2 and #4?
have not found indiviual cylinder scan option yet , just found it odd that the injector pulse width voltage drops on #2 and #4 and not #1 or #3 when missing
What's the percentage of drop that 2ms involves (did you mean ms, not mv)? Is it more than...oh... 10%?
if #1 and #3 at 8 ms #2and #4 at 5 or 6 ms
That's interesting. Did you notice anything odd about any of the right-bank spark plugs when you pulled 'em?
no i origanlly pulled them for a miss before i got the scan tool they all looked even and good burning color
What led you to replace those two coils? Just wondering...
local shop snanned the truck and said #4 misfire figured either coil or injector put coil on and worked great then truck ran for a few miles maybe 200 and started this so i scanned it and it had #8 misfire and random misfires p 0300 i think assuming that the 02 sensors had been heavily coated in unburnt fuel from #4 misfire i opted to replace them
Or the 02 sensors?
Sorry... my screen hadn't advanced...
i just did the front 2
Sorry about all the questions. NO SURPRISE but this is a strange one.
Does the misfire go away in you roll into the throttle at 45?
seams to smooth out under what i would call heavy acceleration
It's not unusual for the Hemi to completely kill an injector when it sees persistent misfire on a particular hole, but loss of only 20-30% pulsewidth is kind of odd. It makes me wonder if the engine itself is having problems with valve action.
And why JUST two cylinders on that bank? The 02 sensor can read and react only to the whole "batch" of exhaust flow streaming past and doesn't know the difference between 2 and 4.
looking at the scan tool fix section they talk about a lot of valve spring problems, wouldn't you notice a spring more than just mid throttle , btw , the scan tool only list inj puls ms for 1,2 3,and 4
I was thinking the same thing. If you're floating a valve at that speed and load ... you'd think it would only get worse with extra speed and load. I want to say you've got a broken spring but it just doesn't fit.
Still, a valve action fluctuation could be picked up on by the MAP sensor which may be why some cylinders have less pulsewidth than others.
This Hemi is too old for cylinder deactivation (MDS) as well...
ok so i'll check the map voltages closely and see if i can find a connection at the time of miss
Yeah, check engine vacuum manually if possible. Tape a mechanical vacuum gauge to the windshield or something and watch for a wobble in the needle that happens only during the misfire phase. A wobbly vacuum reading strongly suggests engine breathing or cylinder sealing isn't consistent across the board.
Compare your vacuum readings between times of misfire and no misfire, expecially for steadiness of the needle.
30-year Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist