What are we missing?

Kyle Diagnostician Philadelphia, Pennsylvania Posted   Latest   Edited  
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Driveability
2008 Mercury Mariner 3.0L (1) 4-spd (CD4E) — 4M2CU81138KJ51240

This vehicle bogs down/loses power on acceleration intermittently. When it happens you can kind of “power through it” and then it’ll start behaving normally until you shut the vehicle off, at which point it starts doing it again. Fuel pressure is 39 psi at idle when viewed through the scanner and 29 psi with a gauge. 

This is the link to the saved PID data: drive​.​google​.​com/open?id=1OoeOG…

The data PIDs in the above link can be viewed with Snap-On‘s Shopstream Connect software available here: snapon​.​com/diagnostics/us…

There are no relevant codes (it had -P2270 Bank 1 ­ Sensor 2 O2 Signal Stuck Lean- due to a broken wire). We’ve performed a back pressure test at the front cat, replaced the fuel and fuel filter, the boss even through a MAF at it with little to no change. I’m hoping someone can see something in the data that I’m missing.

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Chad Mobile Technician
Winter park, Florida
Chad Default
   

I'm unable to view the pids loaded and the link is the application for shopstream. I have it but would need the file​.​ This is a basic question but have you checked global obd2?

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Here’s a link to the PID capture while acting up. drive​.​google​.​com/file/d/1OoeOGl…

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Kevin Technician
Torrington, Connecticut
Kevin Default
 

Do you have data from when it's acting up? Did you check backpressure when it's acting up? Sounds like restricted exhaust or running lean for some reason.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

For any power complaint, start your testing with a FRTD,,,, fuel trim, oxygen sensor voltage, engine load, now take it on a test drive and capture data from idle, WOT up to 60 MPH,,,, if that doesn't nail the problem, you will have a good direction on the next place to test.

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Hey Albin, I’m catching hell for not responding to ya. I meant no disrespect by not doing so, just kinda lost your post in the middle of the rest. I did a WOT test drive, it’s the shopstream file I posted. Unfortunately during that test drive I don’t believe I could get up to 60mph. Plus I‘m pretty sure that the Philadelphia police department would frown on it if I did �.� As an FYI all the…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Hi Kyle, I'm sorry I missed your data capture. Once the silver bullets start flying, most times I keep my head down so I don't get hit. I have taken your capture and edited out the information that is needed to get you a direction to your problem. Over the years, I have used this system for all driveability problems, and I must say, it has made me more money than any other diagnostic approach…

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David Mechanic
Stockport, United Kingdom
David Default
 

Thank you Albin ! You have just put a light on for me. Kind regards Dave T...

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default
 

Albin, I had to Google "FRTD" and stumbled on your article in Motor Age. Great info that I want to implement in my shop.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...Is that gauge reading in NEGATIVE back pressure???...It sure looks like it...left side of ZERO ...opposite where the poundages are marked...what's up with that ?...My BP gauge just shows zero and above. (0 to 8) ...Dan H. ...South Texas...

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Good spot, Dan. We kinda fixated on it being in the green, Doh! Don’t I feel stupid.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

......But,but....WHAT would CAUSE negative BP ??? ...Iv'e never seen negative BP before...must be something NEW. ...Dan H. ...again...

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Gauge is shifted negative. Here’s new BP test front and rear cat at idle and 2500 rpm.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...That makes sense...a simple gauge adjustment...If you had shown it with engine OFF and THEN started it , and razzed it , I would have picked up on what was happening....those are excellent readings...a new gauge might be in your future. ...Dan H. ...again...

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Most definitel.....no adjustment on the Chinese made guage......so a new one is on order. Thank you for catching that. Texans gotta stick together. ...Kyle W.

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Scott Owner/Technician
Brantford, Ontario
Scott Default
 

Fuel pressure during event is?

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David Mechanic
Stockport, United Kingdom
David Default
 

Hi Kyle, could the EGR valve be faulty ?

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Hey Dave I thought it might be an issue, but it’s vacuum operated and I disabled the vacuum to it. The problem persisted. As to the EGR having a mechanical fault I can’t say, but I’d think it very unlikely to exhibit an intermittent condition. I‘m also adding a vacuum test that was done.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

...Get one that goes zero to eight...I never trusted the color band style...I wanna know PSI ...I'll make the decision on a pass or fail based on and accurate gauge...mine is an OTC 0-8 (Ashcroft)...stainless sheathed and oxy fitting permanently attached...nice unit...Had it for YEARS...still works great...you're right about Texas boys sticking together...Dan H ...South Texas...

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David Mechanic
Stockport, United Kingdom
David Default
 

Hi Kyle, I have just read Albins post about FRTD and his analysis of the captured pids. I would like to say thank you because between you both you have enlightened me to the FRTD method . Thanks for sharing kind regards Dave T...

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

That David is exactly why we as techs should participate in this type of discussion. We all can learn just a bit more than we knew yesterday. I’m very grateful for all of y’all’s help.

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LaMont Owner/Technician
Smithville, Ohio
LaMont Default
 

If you trust your mechanical gauge I would wonder if the fuel rail pressure sensor might be over reporting fuel pressure, and if that’s the case, could the PCM be shortening the injector pulse width because it thinks the fuel pressure is higher than it actually is? Just a thought.

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Just for kicks I unplugged the upstream O2 sensors and captured some data. Check out this screen capture.

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Dennis Owner/Technician
Danielsville, Pennsylvania
Dennis Default
 

No other codes in any modules? Another shop that I know, had one that had a bad wheel bearing and false ABS activation. It acted similarly.

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

No ABS activation when the condition occurs.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

What did you gain by that test? When you unplug the o2 sensor, the PCM goes to open loop and your trim data is not reliable. The fuel; trim data is very important, as long as the system is in closed loop.

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Greg Technician
University Place, Washington
Greg Default
 

KOEO. Open throttle slowly and watch TPS voltage and listen to t-body motor. See if they go up smoothly. Had one with bad spot at about 1/3 opening. Caused lack of power and trans to shift fast. There was no codes.

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

Not drive by wire. Has a cable for throttle.

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Greg Technician
University Place, Washington
Greg Default
 

Sorry mine was 2007 Ford Five Hundred 3.0. figured it would be the same.

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Paul Mechanic
Harvey, Illinois
Paul Default
 

I'm seconding Albin, you need to perform a VE Test and add your O2 pids and load. Did you check mode 6 for misfire counts? Sounds like you have confirmed exhaust restriction is not cause and the iat reading when you perform VE Test should confirm by staying the same throughout or possibly dropping a degree or two. How rigid is air filter element as in it isn't collapsing during aggressive…

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Keith Owner/Technician
Etna, Wyoming
Keith Default
 

Also if your mechanical gauge is correct our low on fuel pressure, i trust my gauges before i trust the pcm. As paul stated you kneed to know ve. if you dont have a calculator do a quick search for one or plug the numbers here and we can do it. i am realy interested in the fuel pressure discrepency

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Paul Mechanic
Harvey, Illinois
Paul Default
 

I believe his fuel pressure from pcm is correct-the pcm deducts atmospheric pressure effects or in other words, it's the absolute pressure- I learned that long ago after wasting a lot of time chasing that symptom.

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
 

The gauge is correct as are the values. Based on the info I’ve found as long as the gauge is within 10psi or so of the pie you’re good.

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Daniel Owner/Technician
Ingleside, Texas
Daniel Default
 

…I experiences one that sounded and acted JUST like stopped up exhaust...gave same readings as his on back pressure...so I looked at the air INTAKE...it had sucked UP a plastic grocery sack on the freeway...only difference is that the condition/symptoms were NOT intermittent...this sack was PLASTERED on the air filter medium and made the filter look like the Jolly Green Giant had trounced up…

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

Hey Kyle. I decided not to get involved in this post. However you asked what you are missing. Albin has given you excellent direction. But you don't seem to be responding to him. He's trying to help you. If you could do a flat rate test drive along with a VE test like he said we could help you a lot better than going down all these tangents this post has been. Please understand I'm not trying to…

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Kyle Diagnostician
Philadelphia, Pennsylvania
Kyle Default
   

Hey Caleb, I’m not taking it as a reprimand or in any other way than one tech trying to help another tech. Albin is a great guy and I’ve read many posts from him. As to not responding there is only so much time in the day, I work 6-7 days a week and still try to find the time to spend a bit with my kiddos and the misses. I have posted a test drive where I believe the information asked for is…

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