Secondary Help

Brian Instructor Ohio Posted   Latest  
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Driveability
1998 Dodge Ram 1500 Laramie 5.9L (Z) 4-spd (42RE)
Rough Idle
Stall

Hello all I am looking for advice on this 98 Ram with a 5.9 I have questions about this secondary capture on cylinder #1 trying to understand the downward spike on#1 when #8 should be firing .

It has been around the block and the cannon is hot. cap rotor plugs wires fuel pump iac ckp / cam distributor sensors that I can tell. This is a v6 truck with a 5.9 running on 5.2 ecm , story goes its been running fine for years. On test drive fuel trims buried positive , No Codes, Stalls at times and also unable to get out of its own way at times, I was thinking fuel delivery issue, ( pump etc,) Fuel pressure remains 47 to 50 psi when acting up. Runs just as bad with O2's and map unplugged (Now I have codes! LOL ) Smoke checked for vacum leaks in intake good, I did RC test with pulse in intake and do show something intermittent going on.diag​.​net/file/f6et86hyh…

Any thoughts appreciated as always. I am challenged with the direction that I want to go here.

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Randy Diagnostician
California
Randy Default
 

current ramp coils

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Brian Instructor
Ohio
Brian Default
 

It is single coil distributor system. Randy I must admit that I did not think about ramping the coil as a step in my testing. Thanks for the input. Waiting to see what the customer would like to do at this point.

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Matthew Mobile Technician
Illinois
Matthew Default
 

Just glancing at your waveforms, it looks like you may have multiple issues. There is one cylinder consistently low in the relative compression, and what looks like a possible pressure pulse from it in the intake waveform. It also looks like you have another cylinder pulling vacuum when it shouldn't. I would do some more mechanical testing or pull the valve covers and carefully inspect all of…

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Ray Diagnostician
Ontario
Ray Default
 

CH C shows one cylinder with intermittent low compression CH D shows one cylinder with repeating negative pulses.

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Matthew Mobile Technician
Illinois
Matthew Default
 

I don't think it is a coincidence that they are close to 360 crank degrees apart...

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Brian Instructor
Ohio
Brian Default
 

Thanks for the mark up Ray. I appreciate people willing to take the time and help my rookie eye at these patterns. On a side note I have been playing with my pulse sensor and RC test on my own vehicle (2004 Civic) pulling a plug out clearly shows up on the RC test with amp clamp, however I get unexpected results from pulse sensor in intake, let me know if any of you are interested in seeing …

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Ray Diagnostician
Ontario
Ray Default
 

Yes, I am interested in seeing the captures.

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Brian Instructor
Ohio
Brian Default
 

I am just confused as # 4 plug is out, order is 1342, it seems like the missing negative pulse lines up with #1. I may be not properly wrapping my head around what is going on. diag​.​net/file/f4u33htei…

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Matthew Mobile Technician
Illinois
Matthew Default
 

The engine RPM sped up from the missing compression on 4, so it effects the intake pull on 1.

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Brian Instructor
Ohio
Brian Default
 

Matt, It makes sense to me that the crank will speed up on the dead hole, I do not understand why the intake pull is less, my logic is if piston travels faster downward the pull would be more than the others? Also the # 4i ntake pull looks very similar to #2 / a little less amplitude. Thanks for your help I will continue to learn the pulse sensor.

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Ray Diagnostician
Ontario
Ray Default
 

When cylinder 4 is on the intake stroke, the piston moving down will pull air into the cylinder thru the missing spark plug hole.

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Brian Instructor
Ohio
Brian Default
 

Hi Ray what you say makes perfect sense, however that is not what I am seeing in this capture. Please be patient with me if I am totally missing it i circled it in this picture I see a pull on#4 intake? when I would expect to see no change in pulse do to the air being drawn through the spark plug hole. Matt had mentioned that the change in engine speed would cause a change in intake pulse and I…

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Jj Technician
Massachusetts
Jj Default
 

I see what you're saying. It's like the intake pulls of cyllinders 1 and 4 are behaving opposite of what you would expect. And I've been racking my brain but can't think of why that would be.

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Dmitriy Analyst
Ontario
Dmitriy Default
 

Hi Brian, you are approaching this question scientifically -- trying to explain ALL parts of the waveform so that they are consistent with physics of the process -- and this is absolutely fantastic. In this case the waveform is super-confusing, so we might need to take a step back and revisit a few questions. What is important is to be completely sure we are measuring what we want to measure…

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Brian Instructor
Ohio
Brian Default
 

Hello Dmitriy, Thank you for asking these questions, information that I should have included originally. 1 .Test set up: 2004 Honda Civic 1.7 Spark plug #4 removed, Autoditex pulse sensor with about 3 inch long hose attached to intake manifold hose for purge valve, I have piece of foam to isolate vibration and contact with fire wall, battery was tested before starting this test and was near…

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Brian Instructor
Ohio
Brian Default
   

Hello every one. I have to swallow my pride and share this due to two errors on my end. In reference to my Honda that I have been experimenting with. I started out last Saturday to practice RC testing, normal (known good)and also with spark plug #4 removed. So testing was conclusive and easy to identify that there was a faulty cylinder looking at the starter current. I am learning the…

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Ray Diagnostician
Ontario
Ray Default
 

Thank you for the waveforms, good work!

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Dmitriy Analyst
Ontario
Dmitriy Default
 

Brian, very glad you got to the bottom of this. Many thanks for sharing the waveforms!

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Anthony Technical Support Specialist
Pennsylvania
Anthony Default
 

Hi Brian: There's no such thing as a failed experiment. If you knew the answer, it wouldn't be an experiment. I'm sure that more than one person will learn something from this thread. Hell, it may even be me. :) Guido

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Mickey Technician
North Carolina
Mickey Default
 

Fuel pressure looks good. Fuel trims should want to go rich because the system reads oxygen and with misfiring cylinders there would be a lot more oxygen. I wouldn't think you have a fuel related problem because you wouldn't have just cylinders effected. You might want to check the distributor sync. Most likely not the problem but it's easy to rule out. I have to say you got a lot of guts to…

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Brian Instructor
Ohio
Brian Default
 

Not so much guts LOL. I work to train techs at shops mainly basic electrical testing, scan tool and basic scope usage. This shop lines up the diagnostic jobs that they have not been able to resolve and I work with the techs one on one. Many times I would not take a job wrong engine / wrong computer as I usually have problems that I am not able to resolve.

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Stephen Technician
Tennessee
Stephen Default
 

I am wondering why the s… kv is so high. And why the burn line(s) are in general rolling down, as in too rich? When there is a shorter s… line the burn time looks better. I have to wonder about the coil wire. On the cranking file I don’t see a pull for cylinder 7 but , it’s compression is highest of all. Intake valve? In the WOT part of the cranking file, the signal from the pressure…

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Brian Instructor
Ohio
Brian Default
 

I failed to mention the connection of the pulse sensor on the Dodge was at the purge port at the throttle body. I am waiting to hear if I can get my hands back on this truck, I will be putting the wsp on it to see what the engine vacuum reads.

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Ray Diagnostician
Ontario
Ray Default
 

This is from an 03 Durango 5.9, so we can compare to your 98 5.9 CH A coil wire secondary CH B is WPS in the purge hose at idle. The engine vacuum measures -18.81 in Hg CH D is a sync probe on cyl 1 plug wire

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Brian Instructor
Ohio
Brian Default
 

Thank you Ray will update you with what I find when I get back to vehicle pending approval. I am want the chance to check this thing out, just have to be inside not going to mess with it outside.

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