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Surging/bucking at 51k

Hey everyone I need some help. Ive got a 2015 Mazda CX-5 touring with tech package, it has just under 51k.

A few months back I started to notice my revs were off and keeping me in a lower gear for longer times before finally shifting. Shortly after that I was crawling through a drive thru and my car started bogging like I was killing it. I was going maybe 5 with the throttle open slightly to continue moving forward.

I tried to do research and thought my plugs were dead. Owner’s manual recommended changing them at 75k. That night I took my boyfriend for a drive (completely unfamiliar with how my car drives yet knew something was wrong, he has a 2013 maz 3) and he was like ‘wtf is that?!’ He so easily manipulated the problem at every speed with just bearly being on the gas. We tried multiple speeds 15, 20, 30, 45 and 60 all did it. Only thing we could think was to do a diagnostic. Off to Mazda we went, diagnostics done and boom they said fouled sparkplugs yet never drove my car... ok we replaced them all was good for about 3 weeks then symptoms came back, diagnostic again same answer as before... This time I MADE them go for a drive with me and the tech asked if I had any enemies because it felt like someone put sugar in my tank and his tests said nothing. No codes no lights no answers! Here I am now at just under 51k reaching the end of my powertrain warranty with new oem plugs, new ignition coils, a “recommended” fuel injector cleaner and still no 🤬 clue what is wrong with my car.

Can ANYONE please help me out???? I neeeeeed my baby and I have no idea what else to look at.
 
:
2014 & 2019 CX-5 Touring(s)
With other cars (note: not sure about Skyactive), symptoms like this can occur from a dirty/sticking throttle body butterfly, or dirty MAF sensor. Both should be fairly easy DIY cleaning jobs.

But again, not much experience with this on Mazda engines, so could be wrong and surprised the tech didn't suggest this. See if others comment.

UPDATE: I googled for how-to's:

Throttle body: https://www.mazdas247.com/forum/ind...hrottle-body-mazda-cx-5-skyactiv-g.123855592/

MAF Sensor:
 

AVC

:
'17 CX-5 Select
Many dealers don't want to spend the time to do a deeper diagnostic dive, especially when it's a drivability issue WITHOUT a check engine light. IF you had a cheaper Bluetooth OBD scan tool, the MAF, MAP and fuel trims might better tease out the issue, and you could go better informed to the dealer. My own '17 CX-5 has some light throttle surging, which *seems* to be related to under-reporting MAF at lower engine speeds. I've bought a $30 used but guaranteed unit off of Ebay, from reputable salvage yard. Will see if it fixes it or changes the symptoms at all. I figured it was less hassle than going to the dealer, having them keep it for a day only to tell me "no trouble found"
 
Last edited:

erhayes

Contributor
:
Mazda CX-5 FWD Touring
I wonder if you got a bad batch of gas. You mentioned fouled spark plugs which is unusual at such low mileage. Was it oil or water or something you put in the gas that fouled the plugs?
 

AVC

:
'17 CX-5 Select
Also, in my experience and many others, cleaning hot film MAF sensors, like those on the recent 2.5L Mazdas, does *not* improve the sensor performance. The chemicals in carb/throttle/brake cleaner apparently distorts the very thin sensing membrane and makes the sensor slightly to severely inaccurate at lower air velocities (under 1500 RPM). I've not tried "MAF safe" cleaner, or traditional contact cleaner. If the $30 used sensor fixes my issue, I'll experiment with the original sensor.
 

AVC

:
'17 CX-5 Select
I'd guess the plugs she pulled were not "bad". New plugs may have performed a bit better at lean mixture (the usual reason for surginng) until they got the normal combustion deposits on them.
 

AVC

:
'17 CX-5 Select
BTW, the sensor values that make me suspect the MAF (enough to order a used part to eliminate it):

Fully to temp, idling, 600 RPM, in Park, all acc off:

MAF 1.8g/s (should be 2.4 ~ 2.7 g/s according another member)
MAP 21/22 in Hg (normal according to another member)
Long Term Fuel Trim: +6.
Short Term Fuel Trim: -2.

Graphing MAF sensor output over RPM and under load, I saw some odd spikes and non-linear output. It seems odd, but then not having data from a known good Skyactiv 2.5L, I'm guessing a bit here.

A vacuum leak, purge leak, etc would cause the MAP reading to be lower than normal, AND a low MAF reading.
 
Thank you all for the help!!

I did have the fear of a bad batch of fuel considering I moved from CO to CA almost 2 years ago, I always put mid grade Shell in my car but now it’s $1 more a gallon at every station here and so is Techron. That leaves me with Loves or the little mom and pop stations trying to survive and ever changing prices so I’ve switched to mid Loves. (My boyfriend uses Loves also, his ‘12 Mazda 3 2.0 skyactive has no problems and he’s at 98k. No plug issues and he didn’t even replace his till mine was having problems)

Never did the dealer suggest MAF. I have looked into reputable junk yards myself for a CX-5 to get parts from incase anything was needed. We have an OBD but it’s got a program for the bike not cars. I will mention ordering a reader and see if he says we can just find a program for it and then watch the video on how to clean the MAF in the mean time to see if that helps. I will keep an eye out for the MAP and fuel levels to when checking because that reminded me that I’m slowly but steadily declining on my tank. When I purchased the car in summer of ‘14 I was getting 330-345 on mid gas now I’m hitting 280-290. I figured it was age. I knew vehicles could decline.

Your tips are very helpful thank you all. I enjoy this forum :)
 

AVC

:
'17 CX-5 Select
A $20 ELM 327 compliant Bluetooth adapter + $5 for the app Torque (Android and iOS) can tell you lots.

I found a lot of dealer techs have poor diagnostics skills, especially when there is no OBD error code to point them in the right direction. They are not encouraged to spend a lot of time diagnosing, so they get little deep dive practice. And for some dealerships, reaplcecing an $$ part like MAF without the documentable code, may be more discouraged.
 
:
Pueblo county CO
:
CX-5 Sport 16.5 6M
Have you tried a bottle of Techron injector cleaner? It worked for me once. I had a little stumble sometimes. Stalled at lights a few times.
 

Chris_Top_Her

Banned
Moderator
Contributor
:
San Antonio, Texas
:
'15 CX-5 Miata AWD
Have you serviced your vacuum system with a head cleaner ever? And have you checked for a vacuum line leak?
 

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