5. 7 Hemi Ram - Bad Misfire & Will Not Idle
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Date: 2020-08-05
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Comments and reviews: 10
Kevin
Several years ago, just as I was starting to use compression waveforms as a diagnostic tool, I was working on this older 300C SRT8. It was an auction car, dealer bought it but it had an intermittent check engine light for a P0300 I think. No history on the thing of course and no real info on the concern other than the MIL. I took it out and drove it normally for quite a while, no problem, no MIL. Freeze frame data showed the code set at high RPM, so I gave it some beans and it was fine until maybe 5000rpm then it fell on its face. I don't remember cylinder numbers, but I remember it would show misfires on every cylinder when the problem occurred but still seemed to pick on one cylinder more than the others. Engine was totally quiet, no abnormal noise, ran great most of the time except at high RPM. I messed around with it a bit more trying to get more info from the symptoms and found that it would run poorly even at very light load as long as the engine speed was high. I was scratching my head a little, thinking that maybe the CKPS was scattering at higher frequency or something but kept coming back to the one cylinder showing more misfires, so I decided to throw a pressure transducer into that cylinder for poop and laughter as you say. Sure enough, the exhaust valve opening ramp looked like garbage, no definition and it looked different every time the valve opened. I didn't know exactly what that told me but I knew that the lack of consistency meant that there was a problem with the exhaust valve. So I pulled the valve cover off and found that the very bottom of the spring was broken. Only the first coil, the part that sits on the head, so it was still enough to keep the valve closed but I think it reduced the spring height enough that the valve wasn't closing fast enough at high RPM and blowing a bunch of exhaust into the intake or even just causing enough turbulence to blow out the spark. Either way, one new exhaust valve spring and it was all fixed.
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Several years ago, just as I was starting to use compression waveforms as a diagnostic tool, I was working on this older 300C SRT8. It was an auction car, dealer bought it but it had an intermittent check engine light for a P0300 I think. No history on the thing of course and no real info on the concern other than the MIL. I took it out and drove it normally for quite a while, no problem, no MIL. Freeze frame data showed the code set at high RPM, so I gave it some beans and it was fine until maybe 5000rpm then it fell on its face. I don't remember cylinder numbers, but I remember it would show misfires on every cylinder when the problem occurred but still seemed to pick on one cylinder more than the others. Engine was totally quiet, no abnormal noise, ran great most of the time except at high RPM. I messed around with it a bit more trying to get more info from the symptoms and found that it would run poorly even at very light load as long as the engine speed was high. I was scratching my head a little, thinking that maybe the CKPS was scattering at higher frequency or something but kept coming back to the one cylinder showing more misfires, so I decided to throw a pressure transducer into that cylinder for poop and laughter as you say. Sure enough, the exhaust valve opening ramp looked like garbage, no definition and it looked different every time the valve opened. I didn't know exactly what that told me but I knew that the lack of consistency meant that there was a problem with the exhaust valve. So I pulled the valve cover off and found that the very bottom of the spring was broken. Only the first coil, the part that sits on the head, so it was still enough to keep the valve closed but I think it reduced the spring height enough that the valve wasn't closing fast enough at high RPM and blowing a bunch of exhaust into the intake or even just causing enough turbulence to blow out the spark. Either way, one new exhaust valve spring and it was all fixed.
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Noah
I traded a rusty little Dakota for an 03 Ram with a Hemi just like this and the same misfire that the owner couldn't figure out but it idled fine. He replaced all the plugs, coils, and injectors for a ton of money and gave up on it and I was taking a risk on trading my daily driver for it. I did a compression test and that cylinder was alittle low but it would still built like 60 psi or something. I took the valve cover off and I found one push rod had come out from under the rocker and was diagonal and the top was gently against the valve cover. I pulled the rail off, carefully inspected the rod to make sure it wasn't bent, put it back together without asking any questions and that truck ran mint until I sold it months later and still ran great. No clue how it just came out from under the rocker but it did. I know the 03s and 04s have the valve spring problem and your customer was lucky it didn't blow up the engine.
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I traded a rusty little Dakota for an 03 Ram with a Hemi just like this and the same misfire that the owner couldn't figure out but it idled fine. He replaced all the plugs, coils, and injectors for a ton of money and gave up on it and I was taking a risk on trading my daily driver for it. I did a compression test and that cylinder was alittle low but it would still built like 60 psi or something. I took the valve cover off and I found one push rod had come out from under the rocker and was diagonal and the top was gently against the valve cover. I pulled the rail off, carefully inspected the rod to make sure it wasn't bent, put it back together without asking any questions and that truck ran mint until I sold it months later and still ran great. No clue how it just came out from under the rocker but it did. I know the 03s and 04s have the valve spring problem and your customer was lucky it didn't blow up the engine.
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M. O. S. E
I just did one on my brother in-laws truck. The dodge dealer just put a brand new outta the box motor in 13, 000 miles ago he gets this massive misfire takes it back to the dealer, they pulled the oil pan off and said they were metal debris in the oil and what ever was causing the misfire wasnt under warranty so we told them where to go and I did it the drive way in a couple hours lol.
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I just did one on my brother in-laws truck. The dodge dealer just put a brand new outta the box motor in 13, 000 miles ago he gets this massive misfire takes it back to the dealer, they pulled the oil pan off and said they were metal debris in the oil and what ever was causing the misfire wasnt under warranty so we told them where to go and I did it the drive way in a couple hours lol.
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kain
ill rev up an otfit after fixing a missfire or doing plugs. same as you did in the end whomp, whomp, whooomp!
my boss is like DO YOU REALLY NEED TO DO THAT!
uh. ya.
my boss is an amazing tire guy. and ive taught him a LOT about mechanics (he can do his own GM wheel bearing jobs now)
but mechanics. na
after all. he drives a ford with a 5. 4 3 valve and says its great.
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ill rev up an otfit after fixing a missfire or doing plugs. same as you did in the end whomp, whomp, whooomp!
my boss is like DO YOU REALLY NEED TO DO THAT!
uh. ya.
my boss is an amazing tire guy. and ive taught him a LOT about mechanics (he can do his own GM wheel bearing jobs now)
but mechanics. na
after all. he drives a ford with a 5. 4 3 valve and says its great.
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2Stroke
Extra footage. Made me go from (cry for the customer) to smile at the mechanic.
Your an amazing mechanic.
I just replaced my crankshaft position sensor. Long story short. The 3rd sensor OEM runs great.
The (2) budget sensors. truck was in limp mode, flashing Money light.
That's for the confidence to do these things.
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Extra footage. Made me go from (cry for the customer) to smile at the mechanic.
Your an amazing mechanic.
I just replaced my crankshaft position sensor. Long story short. The 3rd sensor OEM runs great.
The (2) budget sensors. truck was in limp mode, flashing Money light.
That's for the confidence to do these things.
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Gregory
Ive got a 2007 ram 1500 with #8 misfire, every mechanic I talk to says the engine is shot. Can anybody talk me off the ledge on this? They all say #8 yeah its done. Its been sitting and I cant seem to believe this diagnosis. Help, sorry to use this as a forum.
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Ive got a 2007 ram 1500 with #8 misfire, every mechanic I talk to says the engine is shot. Can anybody talk me off the ledge on this? They all say #8 yeah its done. Its been sitting and I cant seem to believe this diagnosis. Help, sorry to use this as a forum.
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Kudzu
If those are so prone to break, wouldn't a good quality full aftermarket set be the longer term fix? Just sayin if it was my truck and I liked it, all the other valve springs have cycled as the same as the broke one. Next one to go may just grenade a cylinder.
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If those are so prone to break, wouldn't a good quality full aftermarket set be the longer term fix? Just sayin if it was my truck and I liked it, all the other valve springs have cycled as the same as the broke one. Next one to go may just grenade a cylinder.
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Quazimoto
Damn
I wish i had a mechanic in my town like you man
Everyone here looking to make 2 grand every job
Lots of liars in the buisness
Yea I'm bent outta shape from getting ripped off
I am always polite enough, probably why
Gawd
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Damn
I wish i had a mechanic in my town like you man
Everyone here looking to make 2 grand every job
Lots of liars in the buisness
Yea I'm bent outta shape from getting ripped off
I am always polite enough, probably why
Gawd
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Jovial
I am so impressed you went right to the problem. What makes that valve spring fail like that? I have an '05 hemi with 234, 000 miles on it and it runs flawlessly and always has. I've done a lot of towing with it too.
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I am so impressed you went right to the problem. What makes that valve spring fail like that? I have an '05 hemi with 234, 000 miles on it and it runs flawlessly and always has. I've done a lot of towing with it too.
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armand
Help! Hemi 5. 7 runs rough and no idle. Have to keep it around 2000rpm. Good compression, changed all the plugs, cleaned throttle body. Replaced fuel pump 10 months ago. O2 sensor is the only codes thrown.
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Help! Hemi 5. 7 runs rough and no idle. Have to keep it around 2000rpm. Good compression, changed all the plugs, cleaned throttle body. Replaced fuel pump 10 months ago. O2 sensor is the only codes thrown.
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