spartanc
Junior Member
Hello everyone! Please strap yourself in because this one is a bit of a doozy. Some background first:
I just purchased a used 2009 Dodge Ram 1500 Crew Cab last month, with about 138,000 miles on it. The body is in stellar shape, the undercarriage is rust-free except the driveshaft and muffler, and the interior is well-maintained. The CarFax is completely clean and the truck only had one owner, who happened to live in the same state as me. It looks like it underwent routine maintenance at the dealership it was originally purchased from until being sold.
I drove the truck for about a week before I got a check engine light one morning at idle, after startup. P0302, cylinder 2 misfire. Well crap.
Now some information about the problem:
As far as I can tell the misfire must be fairly minor, as it only happens after startup and never on the road or when the engine is under load. It's always a P0302 code, though one time there was a P0300 code as well. It doesn't happen everyday, sometimes I will go a couple of days without it happening and other times is occurs every other day. On the days that it does happen, it is the first one or two startups on which is occurs; I can start the truck another dozen times later that day without a misfire. I can't hear the misfire even with the hood open and leaning over bank 2. The motor seems to be performing just fine.
Idling feels a little rough sometimes with a bit of vibration, and there is a soft ticking sound that gets quieter as the engine warms up and lubricates itself (though it sounds like it is in both banks and could just be the "Hemi tick," in which case I don't mind.)
So here's what I've done so far:
I went ahead and assumed that the dealership I purchased the truck from didn't use the proper motor oil when they changed it, and I drained it completely. (I know, a waste :\ ) I put in Mobil1 5w20 full synthetic, and also changed the oil filter w/ a K&N HP-2010.
Next I pulled all 16 spark plugs and replaced them with NGK copper plugs gapped at .045. The plugs definitely needed changed as they had deposits on them, some were slightly burnt, and they were all gapped at nearly .060 (though the plugs from cylinder 2 did not look especially bad.) I also swapped the coil pack from cylinder 2 with cylinder 4. Finally I purchased a tank of 91 octane gasoline and used a bottle of Lucas Oil fuel injector treatment.
Two days passed by without a misfire, but then the CEL came on again and it was P0302 again. Darn.
My efforts escalate:
Now I decide it would be a good idea to invest in a nice tuner that can read/clear codes and do data logging so I purchase one from DiabloSport. I placed one of their less aggressive tunes "Diablo 87" on the truck in the off chance that the current settings had somehow become fouled. Another full tank of premium and another fuel injector treatment as well. I also deactivated MDS just so there would be one less variable moving forward. I also used a SeaFoam treatment (which produced quite a bit more exhaust smoke than I had seen in demonstrations.)
A few days pass by again without any problems, and then the dreaded P0302 comes back once more.
OBDII leads to more questions:
I started playing around with the PID monitoring on the tuner these past few days, and I've noticed quite a few interesting things.
1. The long term fuel trim for BOTH banks 1 and 2 is consistently positive. In addition the fuel trim for bank 1 is more elevated than bank 2, I'm talking 10-14% at startup on B1 versus 5-7% on B2. Furthermore, when the RPM increases and the throttle plate opens up to let in more air then fuel trim for both banks immediately decreases. At RPM's ~4,000 or higher the LTFT for both B1 and B2 reaches 0% and even goes slightly negative.
From my understanding this would be indicative of a vacuum leak in both banks, possibly busted intake manifold bolts? As it's been explained to me a vacuum leak would cause the cylinders to run lean, for which the trim responds by going positive and delivering more gasoline. As the throttle is opened up and the ratio of air entering through the intake versus through the vacuum leak increases, the cylinders stop running so lean and the fuel trim can decrease to 0%.
2. The upstream O2 sensors on both B1 and B2 look fine. Nice periodic motions between ~800 mV to 200 mV. The downstream O2 sensors look suspect, however, with B2 appearing worse off than B1. The voltage levels off at first and adopts a nice periodic motion around ~800-700 mV that almost looks like a flat line. This stops after just a minute or two after startup (usually around the time the misfire would occur) and becomes more variable. The range of these oscillations for B1 starts to increase to about 100-200 mV, while B2 experiences even more variability as the voltage jumps around 200-400 mV.
Worded another way, the downstream O2 sensor for B1 begins to oscillate between 600-800 mV after a few minutes while the downstream O2 sensor for B2 begins to oscillate between 400-800 mV. From my understanding, the voltage of these downstream sensors should be MUCH more steady. The upstream sensors should be experiencing the large oscillations, not the downstream ones.
This makes me think that both of these sensors have become fouled with carbon, further contributing to the issues with fuel trim.
Where I stand now:
So I'm going to run a compression test soon to get some more information on this problem. I think I will be ordering new O2 sensors within the next few days as well, and I'll take a look at the intake manifold for any cracks or deformities. I'm attempting to stave off doing anything expensive until I've ruled out all other possibilities, seeing as this problem is intermittent and non-catastrophic.
The thing that has me scratching my head though is why cylinder 2? If there is indeed a vacuum leak, it would be affecting all cylinders on both banks and not just one. On top of this, a bad O2 sensor for B2 would affect all four cylinders, not just cylinder 2.
This leads me to believe there is a problem with fuel reaching cylinder 2 (I'm not an expert mechanic, just fyi) that is being compounded by other small issues/overdue maintenance items like a warped intake manifold or O2 sensors. Should I try a SeaFoam treatment for the gas tank before looking at purchasing an injector, or would the Lucas Oil treatment have already cleared a clog? Is it even worth replacing the injector or am I barking up the wrong tree?
Any suggestions on where to go next or what to try would be greatly appreciated. I have my father helping me along the way but most of his experience is with older carbureted engines, and I'm learning most of this on the fly. That said, I'm a chemist in my day job so don't be afraid to get real technical.
Thanks,
spartanc
I just purchased a used 2009 Dodge Ram 1500 Crew Cab last month, with about 138,000 miles on it. The body is in stellar shape, the undercarriage is rust-free except the driveshaft and muffler, and the interior is well-maintained. The CarFax is completely clean and the truck only had one owner, who happened to live in the same state as me. It looks like it underwent routine maintenance at the dealership it was originally purchased from until being sold.
I drove the truck for about a week before I got a check engine light one morning at idle, after startup. P0302, cylinder 2 misfire. Well crap.
Now some information about the problem:
As far as I can tell the misfire must be fairly minor, as it only happens after startup and never on the road or when the engine is under load. It's always a P0302 code, though one time there was a P0300 code as well. It doesn't happen everyday, sometimes I will go a couple of days without it happening and other times is occurs every other day. On the days that it does happen, it is the first one or two startups on which is occurs; I can start the truck another dozen times later that day without a misfire. I can't hear the misfire even with the hood open and leaning over bank 2. The motor seems to be performing just fine.
Idling feels a little rough sometimes with a bit of vibration, and there is a soft ticking sound that gets quieter as the engine warms up and lubricates itself (though it sounds like it is in both banks and could just be the "Hemi tick," in which case I don't mind.)
So here's what I've done so far:
I went ahead and assumed that the dealership I purchased the truck from didn't use the proper motor oil when they changed it, and I drained it completely. (I know, a waste :\ ) I put in Mobil1 5w20 full synthetic, and also changed the oil filter w/ a K&N HP-2010.
Next I pulled all 16 spark plugs and replaced them with NGK copper plugs gapped at .045. The plugs definitely needed changed as they had deposits on them, some were slightly burnt, and they were all gapped at nearly .060 (though the plugs from cylinder 2 did not look especially bad.) I also swapped the coil pack from cylinder 2 with cylinder 4. Finally I purchased a tank of 91 octane gasoline and used a bottle of Lucas Oil fuel injector treatment.
Two days passed by without a misfire, but then the CEL came on again and it was P0302 again. Darn.
My efforts escalate:
Now I decide it would be a good idea to invest in a nice tuner that can read/clear codes and do data logging so I purchase one from DiabloSport. I placed one of their less aggressive tunes "Diablo 87" on the truck in the off chance that the current settings had somehow become fouled. Another full tank of premium and another fuel injector treatment as well. I also deactivated MDS just so there would be one less variable moving forward. I also used a SeaFoam treatment (which produced quite a bit more exhaust smoke than I had seen in demonstrations.)
A few days pass by again without any problems, and then the dreaded P0302 comes back once more.
OBDII leads to more questions:
I started playing around with the PID monitoring on the tuner these past few days, and I've noticed quite a few interesting things.
1. The long term fuel trim for BOTH banks 1 and 2 is consistently positive. In addition the fuel trim for bank 1 is more elevated than bank 2, I'm talking 10-14% at startup on B1 versus 5-7% on B2. Furthermore, when the RPM increases and the throttle plate opens up to let in more air then fuel trim for both banks immediately decreases. At RPM's ~4,000 or higher the LTFT for both B1 and B2 reaches 0% and even goes slightly negative.
From my understanding this would be indicative of a vacuum leak in both banks, possibly busted intake manifold bolts? As it's been explained to me a vacuum leak would cause the cylinders to run lean, for which the trim responds by going positive and delivering more gasoline. As the throttle is opened up and the ratio of air entering through the intake versus through the vacuum leak increases, the cylinders stop running so lean and the fuel trim can decrease to 0%.
2. The upstream O2 sensors on both B1 and B2 look fine. Nice periodic motions between ~800 mV to 200 mV. The downstream O2 sensors look suspect, however, with B2 appearing worse off than B1. The voltage levels off at first and adopts a nice periodic motion around ~800-700 mV that almost looks like a flat line. This stops after just a minute or two after startup (usually around the time the misfire would occur) and becomes more variable. The range of these oscillations for B1 starts to increase to about 100-200 mV, while B2 experiences even more variability as the voltage jumps around 200-400 mV.
Worded another way, the downstream O2 sensor for B1 begins to oscillate between 600-800 mV after a few minutes while the downstream O2 sensor for B2 begins to oscillate between 400-800 mV. From my understanding, the voltage of these downstream sensors should be MUCH more steady. The upstream sensors should be experiencing the large oscillations, not the downstream ones.
This makes me think that both of these sensors have become fouled with carbon, further contributing to the issues with fuel trim.
Where I stand now:
So I'm going to run a compression test soon to get some more information on this problem. I think I will be ordering new O2 sensors within the next few days as well, and I'll take a look at the intake manifold for any cracks or deformities. I'm attempting to stave off doing anything expensive until I've ruled out all other possibilities, seeing as this problem is intermittent and non-catastrophic.
The thing that has me scratching my head though is why cylinder 2? If there is indeed a vacuum leak, it would be affecting all cylinders on both banks and not just one. On top of this, a bad O2 sensor for B2 would affect all four cylinders, not just cylinder 2.
This leads me to believe there is a problem with fuel reaching cylinder 2 (I'm not an expert mechanic, just fyi) that is being compounded by other small issues/overdue maintenance items like a warped intake manifold or O2 sensors. Should I try a SeaFoam treatment for the gas tank before looking at purchasing an injector, or would the Lucas Oil treatment have already cleared a clog? Is it even worth replacing the injector or am I barking up the wrong tree?
Any suggestions on where to go next or what to try would be greatly appreciated. I have my father helping me along the way but most of his experience is with older carbureted engines, and I'm learning most of this on the fly. That said, I'm a chemist in my day job so don't be afraid to get real technical.
Thanks,
spartanc
