2000 Dodge 5.9L rough, rich, fumy idle, FTs leaning out heavily

Hey friends, I'm new here.
Been chasing misfires and a rough idle on a 2000 Dodge Ram 3500 Van for some time now and don't know where else to turn.

After replacing the plugs, wires, cap and rotor (twice), the plenum plate and gasket, timing chain, IAC valve, PCV valve, coil, and 02 sensors I don't have anymore misfire codes (p0300, p0301, p0302 were originally the problem). It's performing great when under load.

However, It's running rich and rough at IDLE, and it's really fumy out the exhaust. Still feels like it's missing too.

Fuel trims at idle are leaning out heavily, to around -20/25% collectively after a few mins of idle.
Compression is good.
Leak down tests good (highest leakage is 8% on cyl 1).
I've even tested for cam lobe wear and all cyls seem up to spec.
TB is clean.
Cat is good.
MAP sensor is reading consistent with a vac gauge and looks good on scanner.
TPS is reading consistent at idle, not absolute 0, but consistent at like 10%.
Fuel pressure is right where it should be when primed (49psi). (I DO see fluctuation when running though. Not sure if that's normal...)
Injectors - pulled them and cleaned with carb cleaner and tested functionality with 12v power supply. All good.

I've just started scoping with my new LabNation 2 ch Smartscope and it's a whole new world. Super fun stuff.
The first thing I checked was cam/crank relationship and that looked good. Then injectors. All firing, pintle humps all around.

First of all, any input would be helpful if y'all don't think I've covered my bases here.

Second, I could use some help reading my secondary ignition waveforms. When I probe the coil, a get a strange intermittent tapering off of voltage that lasts through a few firings. It seems to be jumping around among cyl's, but definitely happens on cyl 7 most often.
Is it somehow leftover charge in the coil that isn't getting used?

Take a gander... top green is coil and i'm triggering off of the 7th cyl injector. Firing order across from left is 1-8-4-3-6-5-7-2

Thanks all for any insight!

Some scan data would be helpful. Coolant temp look normal? Dist. cam retard degrees, or whatever Chrysler called it then. Is that normal? Chryslers were the king of substituted values. When somebody says the data was "good', others trying to help might want to see numbers. Nice scope pictures.

Voltage spikes on injector waveforms too low... dont really like some of the high fire lines. If this was my truck bc of low injector spike voltage and lean trims id put new injectors in it.. i see 26 volts on one of the injector controls and minimum you should be seeing 50-60 volts.. so instead of the magnetic field pulling the pintle open really strong ur getting a weak tug

At idle:
Coolant temp hangs out at 195
IAT is at 150 on a 80*F day
Timing advance is all over the board between 5 and 25*
Idle RPM oscillates between 550-650

I am using a bluetooth scan tool (Bluedriver) and there's no option for distributor degrees or anything like that. Wish there was. Unless there's something like that in the ever cryptic Mode 6?

Very good to know about the injectors. There's a 20:1 attenuator on the injector probe. Not sure how to calculate that in to the equation here, but seems like that should make that ~30V spike a ~600V spike, right? There's no way to dial it in on this software like there is on the Pico.

Any thoughts on that top image? What's happening in the middle there on the 7th cyl where it hits high and tapers like that? Thx again!

Here's a capture of the cyl 1 injector for reference (w 20:1 attenuation).
They all look pretty similar. Still look suspect?

OK. cool. What was the vacuum reading at idle when you had a vacuum gauge on it?

No injectors do not spike 600 volts... ignition primary does not even spike 600 volts... if all the injectors are showing 27 volts then theres probably a diode dumping off voltage but it just doesnt appear that way looking at the waveform

John Z wrote: OK. cool. What was the vacuum reading at idle when you had a vacuum gauge on it?

Vacuum bobs a little above and below 12inHG

OK. 12 is too low, and since it's a map system, that'll cause it to run rich, or is a result of it running poorly, which lowers the vacuum, and the ecm will be adding fuel. Did the fuel trims get better at higher rpm - like 2000?

Ninjaxchicken wrote: No injectors do not spike 600 volts... ignition primary does not even spike 600 volts... if all the injectors are showing 27 volts then theres probably a diode dumping off voltage but it just doesnt appear that way looking at the waveform

Gotcha, yeah, then I'm with you - a diode could make sense. Or perhaps a crappy attenuator? Not sure.
It does look just like the other injectors' waveforms and the pintle hump is present across the 5 out of 8 cyl's I tested, so I know they're at least opening and closing.

John Z wrote: OK. 12 is too low, and since it's a map system, that'll cause it to run rich, or is a result of it running poorly, which lowers the vacuum, and the ecm will be adding fuel. Did the fuel trims get better at higher rpm - like 2000?

Right, it seems low, and yeah, FT's definitely look normal at higher RPM.

I've researched this quite a bit now on dodge ram forums and it turns out to be pretty common for these engines to operate in that vac range.
Hard to say what sort of vacuum they left the factory with, but if it wasn't normal, wouldn't the PCM tell the IAC valve to open?

I know you replaced the IAC, but... it kind of feels like IAC or dirty throttle, along those lines. You said it's between 550 and 650 RPM, I feel alot better about 650 than 550 on that engine. Can you see IAC duty cycle command %?

I saw cyl #3 look a little funny in a couple of your ignition waveforms, but they all seem too inconsistent to make a judgement- did you take those at idle? I personally like to also take ignition waveforms under a load in addition to at idle. To me, that tells more about weaknesses in the secondary ignition once you get all of those cylinder pressures up and heat build-up.

Maybe i over looked but i noticed you didnt mention egr valve

Rehd wrote: Maybe i over looked but i noticed you didnt mention egr valve

I like the train of thought, about rough idle that improves under load, but...I would not expect a stuck (or partially stuck) open EGR valve to cause a Rich condition. If anything, that would cause lean.

On another note (and I apologize if you already mentioned you checked this): Did you look at fuel pressure at Idle potentially being too high? Or inspected the fuel pressure regulator vacuum line to see if its wet from a ruptured FPR diaphragm? Could be sucking gas straight into the intake at idle.

TheTechWhisperer wrote:

Rehd wrote: Maybe i over looked but i noticed you didnt mention egr valve

I like the train of thought, about rough idle that improves under load, but...I would not expect a stuck (or partially stuck) open EGR valve to cause a Rich condition. If anything, that would cause lean.

On another note (and I apologize if you already mentioned you checked this): Did you look at fuel pressure at Idle potentially being too high? Or inspected the fuel pressure regulator vacuum line to see if its wet from a ruptured FPR diaphragm? Could be sucking gas straight into the intake at idle.

Thanks, yeah, there's no EGR on this model/yr, just a PCV system which got a new valve and hose recently and seems to be working as it should.

As for fuel, the fuel pressure is a steady 49psi when primed and 49/50 at idle and high rpm - all spec, so that's good.

I wish I could see an IAC position with my scan tool but it doesn't have that data.

When hooked up to individual secondary lines, I'm reading smaller impulses from all other cylinders. This doesn't seem right at all, but maybe I'm missing some theory here.

Here's an example of my cyl 8 spark and injector.



NEW QUESTIONS:

1. Shouldn't I be ONLY seeing the 8th cyl spark on this waveform? Why is there noise from all the other cyl ignitions, post distributor?

2. You can see that the injector is firing 3/8ths of the full four strokes (1 1/2 strokes). Is the fuel injection supposed to happen halfway through the exhaust stroke of a cylinder? Shouldn't it be closer to TDC on the exhaust stroke?

Seanerz wrote: Here's a capture of the cyl 1 injector for reference (w 20:1 attenuation).
They all look pretty similar. Still look suspect?

I see a pintle hump in the waveform so that tells me the injectors are opening to some degree.

However, It's running rich and rough at IDLE, and it's really fumy out the exhaust. Still feels like it's missing too.

Fuel trims at idle are leaning out heavily, to around -20/25% collectively after a few mins of idle.

Fuel Injectors are most likely not the issue unless they are not closing. Doubtful

Can you separate the fuel trims? Short Term and Long Term?

I'd like to see what the Upstream O2 Sensor voltages are at in a graph form at idle Just to make sure its not the O2s causing it, if you unplug the upstream O2s it should go into open loop and use a fuel map. I know you replaced the O2s but I've seen bad ones. Chryslers I think have had issues with aftermarket O2 sensors. I have to look again but I do believe if you unplug the O2s you will see a bias voltage and you should tell us what that is. I think some Chrysler use a high bias voltage which causes havoc when aftermarket O2s are installed.

1. Shouldn't I be ONLY seeing the 8th cyl spark on this waveform? Why is there noise from all the other cyl ignitions, post distributor?

If you are not using shielded leads this can happen. Even if you are, the EMF from other wires will reach your inductor to some degree.

2. You can see that the injector is firing 3/8ths of the full four strokes (1 1/2 strokes). Is the fuel injection supposed to happen halfway through the exhaust stroke of a cylinder? Shouldn't it be closer to TDC on the exhaust stroke?

You can get a relative compression waveform using volts at the battery during cranking. Disable the ignition and then probe your injector, this should give you a better idea as to when its firing. I don't think that is a direction I would go just yet.

Some Chryslers have a 2.5v bias voltage on the ground side which most aftermarket sensors don't agree with and can cause issues. I am not sure if the issue usually means it goes lean or rich. I would assume the sensor would read rich since the sensor wouldn't be able to switch the ground correctly and the ECU would pull negative trim numbers. Just a thought and extending what I mentioned before.

graywave wrote:
Can you separate the fuel trims? Short Term and Long Term?

I'd like to see what the Upstream O2 Sensor voltages are at in a graph form at idle Just to make sure its not the O2s causing it, if you unplug the upstream O2s it should go into open loop and use a fuel map. I know you replaced the O2s but I've seen bad ones. Chryslers I think have had issues with aftermarket O2 sensors. I have to look again but I do believe if you unplug the O2s you will see a bias voltage and you should tell us what that is. I think some Chrysler use a high bias voltage which causes havoc when aftermarket O2s are installed.

Thanks everyone, I'm finally back working on this caper...
These 02s are new NTKs which seems to be the go-to brand on these magnums.
Here's a look at 5 or so mins of idle. Downstream O2 only oscillates when I give it gas and RPMs increase, as you can see bottom left behind the text there.
I'm concerned the Cat is unhappy after all of this running rough and rich. Thoughts?

A couple things I see.

1. 11.2inhg seems low but doesnt seem to be an issue from what I see in the o2 readings.

2. Upstream O2 is not switching from high to low like it should. Its staying relatively around 400-500 which is very odd. It should always switch from .010v to .9v fairly quickly. This would mean the AFR is in the stoich range. An upstream o2 staying in the middle usually means a heater circuit problem or something wrong with the o2 or an exhaust leak.

Do you have any exhaust leaks before the upstream o2 sensors?

Try unplugging the upstream o2 sensor. This should eliminate its effect on the fuel system and the ecm should run in "open loop"

Hold the rpms at 2000 and see if that upstream o2 sensor comes alive by seeing it switching. This test might point to a heater circuit problem... ruling stuff out is what Im doing.

What are the fuel trims just off idle? Say 1500 or 2000rpm.

Now the downstream o2 sensor staying steady at 0.860 is either an extreamly healthy catalytic converter or the afr is on the rich side.