Dakota Forumz banner

1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 · (Edited)
I have a 2001 Dodge Dakota 3.9L 2wd automatic quad cab with just under 230k km or 143k miles. The truck is pretty base aside from air conditioning. For the last two years it's been a constant headache and I have run out of knowledge personally and can't find anyone who's been down the same road. Hopefully someone here can help me.

The truck has a persistent random misfire that acts up the worst about 1800rpm and higher. After much work, the only codes that come up are random misfire, and misfire in cylinders 1, 3, and 5, although through engine work [explained below] I was told the problem is from the truck running too lean. Now here's some history.

A few years ago the truck had a cat inefficiency code which turned out to be a ruined driver's side pre-cat. So the y-pipe with the 3 catalytic converters was replaced as the other side wasn't much better. At this time both upstream oxygen sensors were replaced with bosch oxygen sensors [Later replaced with NTK sensors due to bosch sensors throwing persistent heater circuit codes].

With the Cats being replaced the truck definitely seemed more powerful as it was dragging before, but now it started misfiring. Many sensors and parts were replaced chasing intermittent codes and on other peoples suggestions.
- Full Tune Up [NGK Copper Plugs, NAPA Plug Wires, Thermostat, Distributor Cap and Rotor, Air Filter, PCV Valve, Found and Replaced Leaking Vaccum and EVAP Lines]
- New Ignition Coil
- Throttle Positioning Sensor
- Map Sensor
- Idle Air Control Valve was tested and is fully functional
- Intake Air Temp Sensor
- Coolant Temp Sensor
- Cam Sensor / Hall Effect Pickup
- Crankshaft Positioning Sensor
- Fresh set of Remanufactured and Resistance Matched Fuel Injectors
- Fuel Pressure was tested under load and showed a solid 42psi at the lowest point with little variance
- New Battery
- Vapour Canister Purge Valve
- New Alternator and Water Pump [Maintenance, old ones went during all this]
- Shorty Engine Headers [Someone mentioned that the increased breathing may eliminate some problems. Willing to try anything at this point]

- Transmission had the Governor Pressure Sensor replaced about 3-4 years ago due to it failing, and bands were tuned up and fresh filter and fluid installed. Transmission shop said that the transmission was still in excellent shape.

After all the above and doing a compression test and finding erratic results varying over 70 psi, I removed both cylinder heads. They were both chipped away between the valves causing compression leaks. So both heads were replaced with new [not junkyard] heads with fresh valves and springs. Noted about the old heads, they said that there was carbon build up in the oil valley and under the rocker arms like the motor has been running hotter than it should be for a long time. So I'm told whatever is going on, it's leaning out the fuel/air mix. At this time I also replaced the timing chain, tensioner and sprockets as the old one had stretched quite a bit and didn't look healthy.

At this point is when I got fed up with the bosch o2 sensors and the parts supplier agreed to swap the bosch sensors for the NTKs as they weren't even a year old.

After this the computer was swapped out with two different tested computers from the local junkers and neither of them made a difference. Same exact problem.

I don't think I forgot anything, and after all this work, the truck has had improvement, but the problem has never been completely eliminated. It starts up when the truck emissions system goes into closed loop [o2 sensors at operating temperature] at over 1800 rpm although it really gets bucking at about 2400 rpm. The only codes coming on at this point is the random misfire and the misfire codes for the 1st bank. The Airbag light is on as well because the clockspring in the steering wheel is shot. I was told this won't affect anything but just from curiosity from being in an electronics field, does anyone know if this would affect the circuit the fuel pump inertia switch is connected to? Another suggestion I haven't fully looked into is that the flexplate/flywheel might be warped causing an intermittent loss of the crank positioning sensor at higher rpm? Has anyone heard these before?

I'm open to anyone's suggestions as I'm stretching for any more ideas, and I really don't want to pay the Dealership to diagnose it again as they don't want to try and diagnose it any more. They want me to pay for a new computer because testing with two used but verified computers isn't good enough, and they want to start replacing some of the above replaced sensors with their own sensors without any explained reasoning or diagnosis.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #2 ·
Also has anyone had luck with trying a different dealership to get a diagnosis? It probably doesn't help that the dealership here is just a small one that seems to be sinking.
 

·
Registered
Joined
·
242 Posts
seems like you have covered just about every thing will try to do some research. I would say at this point engine. change every thing sounds new and still the miss has to be in the ignition, but holy crap. maybe a new cam. just throwing stuff out there now. maybe the gear on the distributor and the cam are jumping. there maybe some slack in the dist. shaft bearings causing misfires.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Distributor shaft is tight, virtually no wiggle to the rotor. Had a couple pretty cold days out and one of the new NTK o2 sensors threw a heater circuit code. A different dealership said try taking the headers off and put the stock exhaust manifolds back on because the manifolds aren't holding any heat at all causing the o2 sensors to not stay within operating temperature.

I also found out the headers that were sold to me were designed for federal emissions trucks with an egr, and they just capped off the egr port; wish I knew that sooner. My Dakota has the Cali-Emissions package [3 cats and 4 o2 sensors] so the manifolds are shaped slightly different. Hoping this will fix the problem. I'll post when I get the manifolds back on and if it made a difference.
 
1 - 5 of 5 Posts
Top