Hello all
I have a 2001 dodge dakota quad cab 2wd automatic with the 3.9
The truck runs rough. I did a compression check all cylinders about 110 psi.
Changed the following:
IAC,TPS
Fuel pump
Coolant temp
Crankshaft sensor
All four O2 sensors
Distributor cap and rotor
Cam sensor
Still runs rough! I narrowed it down to NR 4 and 6 cylinders. I removed the plug boot and I am getting spark on both. Checked the injector harness to ensure I am getting voltage to the injector and I am on both. While in operation I disconnected 4 and 6 injector harness and the rough idle did not change. When I removed NR 2 it ran worse. So it's those two cylinders. Any help will be greatly appreciated.

 

have you checked the grounds for the fuel injector harness? also check to see if the ground from the back of the passenger side cylinder head to firewall has a good connection. it sounds like maybe a ground broke or maybe a rodent chewed some wires.

 

The injectors may be getting weak and not opening/all the way. Not sure how to test for it though. Does it clean up off idle?

 

Thank you both for your fast responses.
The ground going to the head is good. I also added a ground wire.
I also swapped the right bank injectors to the left and same issue stayed on 4&6.
I checked the green and orange for voltage 13v to cylinder 4 and hooked up a test light from light blue and purple and it was pulsating.
I drove it last night and got
P0202 inj circ open cylinder 2
P0204 inj circ open cylinder 4
P0300 random cylinder miss
P0304 cylinder 4 miss
P0306 cylinder 6 miss

 

With all you have tried I’m wondering if your PCM is taking a dump as you having moved many things around to try and find the problem and still getting the same results

So I’m thinking the PCM or maybe the distributor

Try a different distributor cap as I have seen some very bad cheap ones on the market from China

Is your Dakota bucking running weird at all or just rough?

If it’s running weird it could be the PCM going out on you

 

No bucking, i rerouted a ground cable, no luck, I opened up the wire loom and found a couple cut wires, not sure if I did it, connected them and nothing same issue. How do I verify a bad PCM?

 

You said you swapped injectors.....have you swapped injector wires?

You say it stays same if you unplug either 4 or 6...did you try one then the other, both at once?

4 and 6 are siamese, right? Try switching wires between the two?

I still think it could be stuck injectors.

Are the plugs showing rich/lean?

My thoughts, even if the injector timing was off ridiculously, the fuel would still be puddles in the intake runner, and would still get sucked in carburetor-esque when the intake valve opens. So I'd be interested in whether the injectors are actually firing.

 

I tried swapping injector harnesses and no change. PCM?

 

hi new to forum have u check plugs to see if ther good sounds like dis. cap to me

 

It seems your compression on your cylinders are to low. Should not be 110. Standard specs are 120 to 150 psi with a maximum variation of 30 psi between cylinders.