I have a 2000 Dakota with the 4.7L and a 5spd. There are 170k miles on it. I have twice now thrown P0300, P0301, P0302, P0303, P0305, P0306, and P0308 codes while driving on the interstate at 70-75mph. Both times going to the same town on a fairly flat road. I don't think I have exceeded 30% load. Neither time did I notice the engine missing or running strangely. It really seems to run great.

A bit of background on what I had done to the pickup immediately prior to first receiving the codes:

About a month ago I finally got the ambition to diagnose why my reverse lights quit working. As I was under the pickup to install a weatherpack jumper on the reverse light switch connector, I noticed that my drive shaft hanger bearing was hashed. I then noticed that the mounting tabs on the tail housing of my transmission were cracked. I ended up getting a salvage transmission and talked myself into the engine mounts being worn likely causing the transmission tail housing tabs to crack. (In hindsight, I think it may have been in an accident long before I acquired it). So I got engine mounts and since my engine oil pan was rustier than any oil pan I have ever seen, I decided to replace that too. To do the pan and engine mounts, I of course had to lift the engine above the crossmember enough to replace the pan. I pulled the old transmission, drained coolant, removed radiator hoses, removed AC compressor and pulled it out of the way, unhooked heatercore hoses, unplugged the wiring harness from all the engine sensors and coils and injectors...

While removing the connectors from the injectors, I noticed a few of the driver's side injectors were leaking at the fuel rail. So I decided to pull the fuel rail to replace the o-rings. When I pulled the injectors, all of the passenger side injectors had visible cracks in the plastic bodies. The driver side ones did not. I also found a coil that was corroded inside. So I went to a salvage yard and got a coil and pulled a bunch of injectors. Every injector I pulled was cracked just like mine. Since the pickup ran great, and I haven't had one CEL or code for the 3 years I've owned it, I reinstalled all the original injectors. I replaced all the coil o-rings and spark plugs. I would bet money that the plugs were original. They all were slightly brown, but all of the center electodes were worn at an angle. There really wasn't much left of the center electrode. Also, while removing the connector from the crank speed sensor, I busted off the pigtail on the original crank sensor. Now that crank sensor was a son of a bitch to get out. It was corroded in so good, I ended up busting it up with a chisel and pounding it out from the inside once the pan was removed. I replaced the crank sensor, installed the pan, replaced the engine mounts, bolted up the engine, buttoned up the radiator hoses and compressor and all that. After I got the flywheel machined I reinstalled that and a new clutch. Installed the transmission, exhaust and trans crossmember, driveshaft with new ball joints and hanger bearing, blah blah.

I started her up and she purred like a kitten, like she had since I bought it. I didn't expect any better or worse I guess. So I drive it to and from work 10 miles each way for a week. No issues. The next saturday, I drove it about 30 miles on the interstate and my CEL came on. I plugged in my code reader (I carry one in every vehicle), and to my surprise I have misfire codes on every cylinder but 4 and 7. I cleared the codes, got my groceries, and drove 30 miles home. I then popped the hood and noticed I hadn't tightened the upper radiator hose quite enough and coolant leaked from the hose and was being blasted around by the fan. I diluted all the coolant with water and let it dry. I pulled the coils to cylinders 1, 2, and 4 I believe as they were easiest to get to without pulling a bunch of **** off and there wasn't any moisture in the bores. Anyway, I then drove it for about 250miles, with maybe 10 trips too and from work and a 150 mile round trip on a highway at 62mph with no problems. Then today I drove again on the interstate at 75mph and I noticed the CEL was on when I was pulling back on the interstate for my trip back home. I checked the codes and sure enough, a random misfire, and misfires on 1,2,3,4,5,6,8. There is absolutely no indication drive-ability wise that there is a problem. I cleared the codes when I stopped for gas 20 miles into my return trip because I hate looking at that ****ing light. When I got to the gas station and re-checked the codes before erasing them, only the random misfire and misfires on 1,2,3,5,6,8 were present. So identical to the codes from like two week prior. I got home and checked things over under the hood. There is nothing I can see that would be effecting that many cylinders. I shook around the engine harness in multiple places in case there ire some chaffed wires somewhere, but it idled fine and no codes appeared.

Any idea where to start with this? I am leaning toward replacing the crank sensor. I'm pretty sure I got like the third cheapest one on Rockauto. The consistency of codes is strange. The only other thing I can think of is that my fuel pressure could be low or something. What should I be seeing at the rail? 60psi? Pretty sure I have a gauge somewhere. It would be quite the coincidence if I am just happening to complete a drive cycle both times driving to the same town for groceries. But that still doesn't explain the misfire on 6 cylinders. About three months after I bought the truck, 3 years ago I did drop the fuel tank when I replaced all the brake lines. I didn't replace the sender/pump, but I did pull the unit and the sock wasn't full of ****. The truck runs good, so I'm going to continue driving it. Any insight is much appreciated. Thanks for reading my novel.

 

One of the 4.7 guys will have to chime in and verify, but..

1) great of you to have the ambition to service everything while you had it apart. That should bring you many more years of service.

2) The 2-piece upper radiator hose is a joke. I had one explode going down the highway - that was fun. But caused no electrical harm.

3) Rail pressure us ~50-55 psi

4) Misfire monitors are generally operated via the upstream oxygen sensors with relativity against the crank and cam position sensors and the timing of the coil firing. I didn't see a mention of O2 sensors anywhere, but get a good set of genuine NTK's. the knockoffs/store brands and Bosch's dont play well.

 

Thanks for the reply Magnethead.

1) After years of working in shops paying my way through college, I’ve learned that no one cares about your vehicle like you do. They just slap it together to get it down the road. I actually had a BMW 550 before buying this old turd Dakota. I bought an acreage on gravel after I got out of the Army and after two years of the BMW sitting in the shed while I drove the Dakota, I finally sold it. Something about this Dakota has grown on me. Probably the LSD and 3.92 gears. I put a decent amount of money into the thing, but I don’t like anything new to be honest.

2) I did replace the upper 2 piece hoses and filler T as well as the lower hose while the coolant was drained.

3) I just pulled out the fuel pressure/vacuum gauge I have and have never used. It’s a low pressure 10psi one. Guess I’ll find a higher pressure one.

4) I was monitoring the O2 sensor voltages on my cheap scanner after I had the pickup back on the road and they appeared to be working fine. This thing doesn’t have sensors for the left and right bank of the Y pipe, just one before the catalytic converter and one after. I don’t see how the upstream sensor would factor into misfire recognition, but you could be right. I’m just resistant to through an upstream sensor at it when I’ve seen that it’s at least not dead. I’ll be the first to admit that I’m not positive what the voltage should be at in certain situations.

I guess I’m leaning toward the crank sensor since that is something I touched, when I didn’t have any problems before. I just pulled the crank sensor and the crank wheel hasn’t been contacting it. I know the wheel looked good when I had the pan off. I’m confident I didn’t mess it up with the chisel when I was in there.

 

What kind of plugs do you have in it?

Crank sensor isn't suppose to touch the tone ring..... just needs to be close. It's essentially a hall-effect switch.

 

Hey You, I’m aware of how a Hall effect switch functions. I was commenting that it wasn’t contacting the sensor wheel because of tolerances in after market parts. It wouldn’t have surprised me if the replacement one was too long and that was causing my issue. That’s why I pulled it to check.

 

I had to wrap my brain around it too. The pushrod engines don't have knocksensors, so the PCM has no way of knowing if there is an actual misfire. Instead, it takes that super fast lean-rich-lean-rich coming from the exhaust pulses and somehow figures out which cylinder is which pulse, or if there is a pulse missing. But the pushrod engines also use an 8-window HE CPS instead of a 16 (then later, 32) tooth HE CPS. I also don't know if the OHC engines have knock sensors or not.

I don't have a 4.7 so I don't claim to know anything about them more than what I read online. I let Dodgevity and a couple others cover most of the 4.7 stuff.

 

The plugs I put in are Champion RC12MCC4’s, gapped to 0.040” with a feeler gauge. I had to pull one to check as I didn’t remember. I pulled #1 and #6. I pulled 6 because that was the coil I replaced. The original coil was part #56028138 and the junk yard one was 56028138AD. I assumed that the “AD” was just a change to thicken the o-ring groove for a thicker o-ring to mitigate corrosion. I just cleaned the original coil out with contact cleaner and a bore brush and installed it.

Anyway the #1 plug had a little bit of brown on it, while the #6 plug was completely white. I pulled #4 plug and it was completely white as well. I’ll get a fuel pressure gauge to verify fuel pressure.

is it likely that I am having a lean misfire? If fuel pressure is good, do I likely have a vacuum leak? I have noticed that when I blip the throttle, it takes longer than I’d expect to return to idle. It has done this since I’ve owned it. I have sprayed around the intake with it running with brake cleaner and wasn’t able to ever find a leak source.

 

Very first thing I'd do is replace the crank sensor with a Mopar sensor.

 

I have a new crank sensor coming. I just checked fuel pressure and it is between 48 & 49psi. It’s under spec of 50-55psi, but I’m not changing the pump/sender for 1psi.

 

That's decently acceptable. The PCM does not monitor FPR so that won't throw a code. It also shouldn't throw off the AFR.