Skyactiv 2.5L NA Low speed sluggishness SOLVED

[AVC]

DELETED

 

[clownshoes2]

This is why I love the internet.

 

[HyFlyer]

Thanks for taking the time to type it all up for the forum. I appreciate your report.

 

[181962]

@AVC I think it's time for you to upgrade to a spanking new CX-5 with cylinder deactivation...so you can diagnose that one with similar annoyances.

 

[cz5gt]

have you ever had a pcm and tcm version update?
pretty much the soft update for 2.5na fixes that issues in about 95% of the time.
There was a mess up with the control logic in certain 2017-2019 years which is fixed in the later yrs

 

[AVC]

@AVC I think it's time for you to upgrade to a spanking new CX-5 with cylinder deactivation...so you can diagnose that one with similar annoyances.

The first thing I'd do is determine if there was a way to disable cylinder management. Is some cases, like the Honda j-series V6, you just fool the PCM that the coolant temp never gets to 167F, where the PCM then keeps VCM disabled. My '12 and '20 Pilots have those defeat devices.

 

[dunhillmc]

Not sure what "update" you are referring to, but neither dealer knew of any updates for that issue, when I asked then directly. I also scanned all the published TSB's, periodically checking avery 6 months or so. There is a known PCM update to address drivability in high altitude, high temperature, but that didn't apply to my issues which had symptoms at all ambient temps (getting worse at high ambient temps) and my 600 ft altitude.

Pretty sure when I pull the valve cover, I'll find a physical issue with the cam chain sprocket or pulse wheel, that was likely there from the factory.

[EDIT]

I calculated the timing shift for one tooth on the cam chain sprocket; 8.6 cam degrees. So that rules out the chain jumping or installed a tooth off. That leaves the pulse wheel.

PCM and TCM calibrations are regularly updated both for performance improvements and for fixing bugs that pop up over the years. Part of the certification process for CPO Mazdas is to update the PCM/TCM/Connect software to the latest versions. I just had the PCM software on my 2017 Mazda6 updated and it feels like a whole new car now

 

[Buzzman12]

Ok, you'll have to excuse my ignorance here, but is updating the PCM the same as updating the info system, or are we talking apples and oranges?
Is there a way to tell what version is in the PCM?

 

[Jack Rabbit]

All i gotta say is that's a hell of a piece of expensive equipment to play around with. One thing to experiment on a 15 year old project car. Quite another to play with a 5 year old transport.

 

[cz5gt]

Ok, you'll have to excuse my ignorance here, but is updating the PCM the same as updating the info system, or are we talking apples and oranges?
Is there a way to tell what version is in the PCM?

its different than the infotainment.
pcm controls the engine, tcm the gearbox, simply said

 

[AVC]

I just had the PCM software on my 2017 Mazda6 updated and it feels like a whole new car now

Specifically to what version or TSB #? Would say on the service order.

 

[dunhillmc]

Specifically to what version or TSB #? Would say on the service order.

That's never listed. Whatever the most recent version is, is what's installed. The update comes through the Mazda system when they hook the vehicle up to the computer. Most dealers will charge an hour's worth of labor to do an update unless it's something under warranty (ie, a PCM and TCM update would be charged for 2 hours of labor, even though they actually take about 20 min each. That's why I only did the PMC)

 

[AVC]

Never? Maybe for your dealer...

 

[dunhillmc]

Never? Maybe for your dealer...

Unless the tech manually writes down, "updated PCM per customer request. version xxxx-xx-xxxx"

The Mazda system only installs the latest versions

 

[ADS-B]

I had been for the last year using manual shift mode to keep RPM's up where it was more responsive around town.

I've been using manual shift mode since my first CX-5 just because of the sluggishness that your were talking about. In my opinion, the manual mode is the way to go with Mazda CX-5.

 

[madar]

A bit long..

So, ever since i bought my '17 CX-5 in 2019, I've been really frustrated by

1. a launch, tip-in hesitation that gets REALLY annoying in hot weather,
2. very sluggish throttle response at slower speeds and 87 octane fuel,
3. along with some slight but noticeable surging in acceleration in city driving.

By the time it got to 40 mph or faster, and running 89 or higher octane, throttle response was decent, but not urgent. 91 octane was by far the best overall drivability. Yet, the around town drivability has been distracting.

In almost 3 yrs time I had carefully measured, and eliminated as root causes;

1. MAF curves for 4 or 5 sensors (there are tangible variations among sensors),
2. careful measurements of primary and secondary ignition (virtually perfect waveforms and very rare single count misfires)
3. careful measurements of upstream and downstream sensors. Virtually perfect and good as compared to other skyactivs
4. careful tracking of fuel trims, ignition timing and other ODB data. Pretty much spot as compared to other skyactivs
5. on-rail cleaning of injectors.
6. after making my own in-cylinder pressure transducer, compared crank sensor (CKP) timing to TDC. Perfect; 20 crank pulses = TDC.
7. I previously measured both cam sensors (CMP-I, CMP-E), but didn't find any known good waveforms that referenced cams to CKP pulses on the various "free" waveform sites. Until the last two weeks...

A tech on Rotkee published a scope capture with CKP, CMP-E and CMP-I together, for the conditions of idling with the intake cam VVTI motor power disconnected and the exhaust cam VVTI control solenoid disconnected.

I measured my CX-5 in same fashion and discovered that the exhaust cam signal was spot on at 20 pulses of the CKP wheel (same as Rotkee waveform), however the intake cam signal was at 37.2 CKP pulses, as compared to the Rotkee waveform intake cam signal , where it occurs at 35 CKP pulses (exactly 90 degrees different than exhaust cam under those conditions). I double and triple checked the measurement. The intake cam was indeed 2.2 CKP pulses late (retarded), which is about 13 CKP degrees or 6.5 CMP degrees retarded. See attached image.

The next questions were why? How does the PCM *not* set a code for this?

After studying the service manual and internet photos of the valve train and closeups of the camshaft pulse wheel, there seems only two possibilities; the timing chain was off a tooth for the intake cam, or the intake cam pulse wheel was pressed onto the cam incorrectly, or the pulse wheel had shifted. As for why the PCM didn't flag this, unknown; maybe within some operational tolerance?

I any case, the PCM is able to command a certain cam position (in degrees) and the VVTI system complies perfectly. What the PCM apparently doesn't know, is that the cam pulse wheel is lying about the physical location of the lifter lobes.

So, after noodling on this a while, it seemed that I could either pop the valve cover, check the pulse wheel position on the cam (not sure if there are alignment marks), and then attempt o move the pulse wheel. OR I could fiddle with the cam sensor and shift its position to detect the pulse wheel EARLIER. I chose the latter.

I calculated needing to shift the nose of the sensor about 3mm UP, which meant about a 1.8mm gap at the top of the sensor mounting flange. I loosed the bottom sensor bolt and wedged in a small horseshoe shaped piece of circuit board (~ 1.7mm), and applied a dab of adhesive caulking to keep it in place.

So...a SHOCKING change in overall throttle response; most dramatically at low speeds, but definitely noticeable at freeway speeds. I wont have a chance to measure the CKP/CMP-I waveform for possibly 10 days to see how close to 35 CKP teeth the CMP reference pulse is.

My long term plan is to remove the valve cover and see whether it is a wrong pulse wheel position or if the timing chain is off a tooth. Then decide what (if anything) I want to do about it. Depends on how close to nominal my DIY intake cam sensor shim is working, I think.

Anyway, for anyone else who has a skyactiv vehicle that seems much more sluggish than an another CX-5 or Mazda they've driven, this might be worth looking into. I will note two different Mazda dealerships looked into this specific complaint and claimed all was normal. No codes, fuel trims normal, cam timing PIDs all normal, no misifres, etc.





View attachment 313453

Yep, pretty much my past experience with other dealer brands...if there's no code thrown then there's no problem.

 

[AVC]

I've been using manual shift mode since my first CX-5 just because of the sluggishness that your were talking about. In my opinion, the manual mode is the way to go with Mazda CX-5.

Let me be clear; my issues aren't related to the somewhat MPG oriented transmission programming of the CX-5, but rather to lower engine output (torque) and sluggish throttle response, most exacerbated at lower speeds and for the intake/exhaust valve strategy which, because the intake cam is not physically where it reports to be, causing significant ADDITIONAL drivability aggravations.

 

[cz5gt]

isnt the intake cam advance/retard controlled electronically?

 

[clownshoes2]

So, for the laymen here...what can we do if anything to fix this problem? Is there a certain TSB we can ask for at the dealer or some other fix?

 

[ColoradoDriver]

A bit long..

So, ever since i bought my '17 CX-5 in 2019, I've been really frustrated by

1. a launch, tip-in hesitation that gets REALLY annoying in hot weather,
2. very sluggish throttle response at slower speeds and 87 octane fuel,
3. along with some slight but noticeable surging in acceleration in city driving.

I feel like every Gen 2 CX-5 loaner I have ever driven was significantly and noticeably worse than my 2014 in all of these points you mentioned. Last time I had one I was extremely bothered by the lack of acceleration from a stop behavior it exhibited versus my own 2014.

It may be "the same engine" as my car (CD and other changes aside), but whatever they did to the Gen 2's with the NA engine, they messed it up in my opinion.