In cylinder analysis help

Matt Owner Roxboro, North Carolina Posted   Latest  
Unsolved
Driveability
2017 Jeep Patriot Latitude 2.0L (A ECN) 5-spd (T355)
Reduced Power
Poor Idle

I am hoping to get some input on some in cylinder waveforms. I have enough experience to know when something is NOT good but still need some help with the WHAT it is. This vehicle came in with a low power complaint about 8 weeks ago. After test drive and some basics, I wanted to rule out CATS and timing so I decided to brake the scope out. The jpeg image shows the in cylinder on #1 with cam and crank that I took on the original visit. After reviewing the capture there is some interesting repeatable bumps in the CKP waveform but all of my timing marks seemed to line up perfect. I thought maybe play in a pulley somewhere? The customer had to pick the vehicle up that day and I did not get a chance to see the vehicle again until today. I retraced some of my original steps but wanted to add in the exhaust and intake and do some cranking versus running. I did cranking cylinder test on #1 with exhaust, intake, and an RC test. The RC test showed low compression on #1 compared to the other cylinders and it also showed leaning towers during cranking. I did a running test at idle and added a primary ignition sync to #1 to replace the current clamp. Knowing that #3 was the companion cylinder I repeated the same test on # 3. I took my bore scope while I was there and looked at the piston and valves on both 1 and 3. There was a lot of carbon but I could not see an obvious sealing problem. My questions are mainly how to analyze the exhaust and intake to determine whether the problem is mechanical or valve timing. If mechanical how to pin it down to a specific valve or action on a specific cylinder I see some things that stand out in the two waveforms both in cranking and running, but I dont know how to interpret a "cause" for them. I would love some input from everyone to see what I am missing and learn how to analyze these better. 

0
Helpful
Michael Business Development Manager
Las Vegas, Nevada
Michael Default
 

engineangel​.​com enginepolygraph​.​com

-4
Default Ð Bounty Awarded
Chris Diagnostician
Commack, New York
Chris Default
   

I believe you are seeing a small voltage drop on the voltage traces. I would check your ground

+1
Default Ð Bounty Awarded
Chris Diagnostician
Commack, New York
Chris Default
 

Also this

0
Default Ð Bounty Awarded
Chris Diagnostician
Commack, New York
Chris Default
 

And this

0
Default Ð Bounty Awarded
Chris Diagnostician
Commack, New York
Chris Default
 

I see you also have leaning towers, meaning the same volume of air is not in the cylinder from compression to expansion. this coupled with noise in the exhaust, and not in the intake, would have me look at leaking exhaust valves. Yes I said valves. I would like to see a few more in cylinder captures. Maybe perform a leak down to confirm

0
Default Ð Bounty Awarded
Ray Diagnostician
North York, Ontario
Ray Default
   

Chris, the pressure transducer hose is in cyl 3. The cyl 3 COP is connected to a spark tester.

+2
Default Ð Bounty Awarded
Chris Diagnostician
Commack, New York
Chris Default
 

well, nevermind than...

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Chris. Thanks for the input. That was the conclusion I was leaning toward based on the asymmetrical towers and the high pressure durring the exhaust plateau. I also did a pressure test with the gauge at the 02 sensor just to rule out back pressure from the exhaust even though it didnt look like a plugged exhaust in the snap throttle sections. I just want to clarify my capture and ask some other…

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

I assume you are talking about the primary ignition?

0
Default Ð Bounty Awarded
Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...What program is best for looking at your attachments?...I can't view them...Dan H.

0
Default Ð Bounty Awarded
Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...That was for Matt's pix...Dan H.

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

They are Pico Data Files. You can download the software from PicoAuto for free. If you would like I can share a few image files. Let me know

0
Default Ð Bounty Awarded
Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...Tanks Matt...I'll look to see if I haven't already downloaded it...thought I had...Dan H. ...South Texas...

0
Default Ð Bounty Awarded
Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

Have to download the PICO software to view the files. Its free.

0
Default Ð Bounty Awarded
Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

Tanks Caleb...I'll do that...thought I had already...Dan H. ...South Texas...

0
Default Ð Bounty Awarded
Ray Diagnostician
North York, Ontario
Ray Default
   

Matt, the interesting repeatable bumps at the bottom and at the top of the CKP and cmp wave forms are normal and are caused by the COP primary winding current draws.

+3
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Ray. Im just trying to clarify my question and make sure we are talking about the same thing. In the image file in the first batch of uploads I have it labeled as "What's this" That ripple upward is the ignition?

0
Default Ð Bounty Awarded
Ray Diagnostician
North York, Ontario
Ray Default
   

Matt, we are talking about the same thing. The "What's this". The ripple upward is the voltage drops caused by the loads of the COP primary winding current ramps. You can also see the same ripple upward at the bottom of the ckp and on the cmp signals

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Thanks Ray. That has been bothering me for 8 weeks. I would not have thought that. I have seen the show up as noise in the ground but not a ripple like that. I was thinking it had something like a pulley causing an air gap change.

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

The companion for #1 is #4. FO-1342. The valve timing in both cylinders looks appears normal. The intake waveform looks symetrical but does not line up with the cylinder TDC's like usual. I'm wondering if the waveform is inverted? That way looks more normal. The exhaust waveform looks symetrical on the cranking capture but has large high spot and is very distorted on the running capture. It…

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Here it is marked up. How would the waveform become inverted? Not questioning you just asking how they could get that way in the set up? Thanks for clarifying companion cylinder for me. I guess that is the wrong verbiage. I was thinking of when #1 was on the intake stroke that #3 would be the cylinder on the exhaust stroke. Thanks for the thoughts.

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
   

Attached segment of a cyl1 tower has vertical cursors crossing the upper horizontal cursor. The horizontal cursor is at a place, near the base of the tower but above effects of valve actions. The vertical cursors are placed, one on each side TDC mark, where the horizontal cursor crosses it. This sets a point of equal pressure in the cylinder, one before TDC, the other after TDC. The vertical…

0
Default Ð Bounty Awarded
Ray Diagnostician
North York, Ontario
Ray Default
 

Stephen, it looks like the WPS AC coupled in the intake inverts the pressure. In my first capture, CH C is the FLS in the intake and a FLS pulse is pulled down when the intake valve opens during the intake stroke. In the second capture, the Math channel is the WPS in the pcv hose inverted. Again, the WPS pulse is pulled down when the intake valve opens, during the intake stroke

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Thanks Ray

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Ray, Is that something that should be inverted with every intake capture with the WPS or is it just when it looks off? I also marked my cylinders for the intake and exhaust and inverted the intake capture to show correct direction as you pointed out. Can you confirm that I have them labeled correctly. Also are both the negative and positive pressure changes used for analysis in both waveforms?…

0
Default Ð Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Hmmmm, WPS500 is not known to invert any signals in any of its modes. However, I have seen people using banana jacks extension leads with both WPS500 and FLS, and flipping wires is totally possible with that setup. It's better to test the equipment. Just like with touching battery positive with a test light before starting testing... blow into your pressure sensor and observe the trace going…

+1
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I wondered about reversal, but assumed the connections were BNC and discounted it. I don’t think that the original is reversed but was at a loss for how to explain it.

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Stephen thanks for sharing. The waveform you marked is one of the running captures. The one that appeared leaning to me was the cranking captures. I used your method to mark up and measure here is what I came up with. Let me know if I applied this method correctly.

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Your mark up is correct. I had seen that but used the running since it didn’t show as much loss. I checked the cam spec and the valve timing is symmetrical so it would appear that the cylinder is leaking. I would expect that to show a bigger exhaust pocket though. Whether that is a concern is another question. Leakdown test allows for 15% or more before calling it significant. I don’t think it…

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Stephen I had the same question on the exhaust pocket. Even the running vacuum in the exhaust pocket seemed low to me. I took this as another sign of a sealing issue. Thanks for your thoughts on the intake capture. A BNC to BNC was used for the hookup. I will test the WPS that was used just to verify there are no issues with the sensor. As for where I chose to connect to the intake, the intake…

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Here is a link to Utube video. He discusses why compression changes at different speeds with examples. The compression spec is what the engine should do cranking,WOT. Values below that are abnormal. So is 20 pounds less significant? Although as pointed out, the length of the compression hose connection, or the hose itself, can cause readings to be lower than actual. Checking with a mechanical…

0
Default Ð Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Stephen, here is an interesting experiment: check the exhaust pulses in running captures for cylinder 1 and cylinder 3. Do they stay in the same place (relative to cylinder 4) or move with the cylinder under test?

0
Default Ð Bounty Awarded
Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Of course, I knew the answer before I checked, but I did check. The “pulses” do move. So the anomaly is something in the test setup.

0
Default Ð Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Matt, thanks for clearing up about the BNC-BNC setup. Now, with high running compression numbers, you are on to something. Carbon build-up can be a contributing issue (would love to see the borescope picture). Also, your idling running compression values are higher in the first half of the capture due to higher intake manifold pressure (where the cylinder starts its compression), just -6psi. At…

0
Default Ð Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

“I did cranking cylinder test on #1 with exhaust, intake, and an RC test. The RC test showed low compression on #1 compared to the other cylinders...” You have a pressure transducer in cylinder #1. Because of that the RC test would show it lower than others even if all of them have equal compression. Always start with the RC test without any alterations to the engine.

0
Default Ð Bounty Awarded
Matt Owner
Roxboro, North Carolina
Matt Default
 

Thanks Dimitriy, I did wonder about that. Thanks for verifying it. I should have grabbed that first.

0
Default Ð Bounty Awarded