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I have a 2015 6 with the 6MT transmission. When I accelerate at a normal pace I frequently get hesitation/lagging in the low/mid RPMs. Before this car I had a 2015 with the automatic that I had bought new. Both had a similar issue. Has anyone else had this and found a solution?
 

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You may be running into the ECU pulling timing; these engines run really, really close to the edge of detonation due to the high compression ratio and dynamically tune it out with both ignition timing and valve phasing. In addition the A/C system on this vehicle is a cycling one (not constantly engaged with a dynamic RCV to control load) and that can momentarily feel like this as well when the compressor kicks on, especially under light acceleration. American and Japanese cars typically use cycling A/C systems; European vehicles tend to be RCV-modulated instead (with exceptions in both cases, of course.)

If it's the A/C there isn't a "solution" since it's not the engine per-se. Eliminating potential ECU timing/valve pulls of the compression can be tested by running the fuel nearly empty and putting some 93 octane in there; if it materially lessens the incidence then that's what's going on. It's not harmful but you decide whether the additional price of premium fuel is worth it or not (it isn't for me; you can almost-completely avoid this happening by staying out of the operating regime where it happens, especially in hot weather.)
 

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You may be running into the ECU pulling timing; these engines run really, really close to the edge of detonation due to the high compression ratio and dynamically tune it out with both ignition timing and valve phasing.
The good side of this, to my way of thnking, is that fuel/mixture enrichment is NOT the prevalent or primary way of dealing with this... and so fuel dilution of the motor oil is not often reported on at least the normally aspirated SkyActiv-G 2.5. Compare this to the prbs being experienced with Honda's 1.5T engine.... CRV, Civic, Accord... :| .
 

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What's your mileage? Do you feel the engine idling when you are stopped?

The first culprit would be excessive carbon buildup/deposits on the intake valves. I would also suggest getting the OV ECU tune, which greatly increases low-end torque/ response.

Tickers suggestion to try a tank of 93 is pointless because as many of you should no, the NA Skyactiv is only tuned to run on 87 from the factory. The ECU tune, especially for higher octane helps reduce a lot of the predetonation which occurs at lower RPM.
 

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I have the OV Tune on my vehicle and the original file, so I can swap them at-will.

It pulled timing originally when I bought it, and still does under certain driving conditions with it being more-noticeable in hot weather on 87 octane. The easiest way to not have that happen is to not run the engine in that part of the operating envelope.

Suggesting that the "first" (e.g. most-likely) culprit is a mechanical problem requiring disassembly is ridiculous, especially on two separate vehicles sequentially and immediately. Odds are the is exactly nothing wrong with the engine at all.
 

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I have the OV Tune on my vehicle and the original file, so I can swap them at-will.

It pulled timing originally when I bought it, and still does under certain driving conditions with it being more-noticeable in hot weather on 87 octane. The easiest way to not have that happen is to not run the engine in that part of the operating envelope.

Suggesting that the "first" (e.g. most-likely) culprit is a mechanical problem requiring disassembly is ridiculous, especially on two separate vehicles sequentially and immediately. Odds are the is exactly nothing wrong with the engine at all.
So keeping the RPM's closer to 3000RPM results in better operation?

I'm willing to bet that both engines had some degree of carbon deposits on the intake valves; albeit minor. This without a doubt could be some of the lag you feel before the engine is in the optimal part of the powerband. While Mazda has done a good job of making this issue practically non-existent even with the absurd quality of fuel available in North America, but there have been documented cases on the CX-5 section over at Mazdas247 where our engine had tons of deposits at rather low mileage (city driven)
 

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No, I'm saying that any such "deposits" have nothing to do with the "lag."

There are multiple factors that Mazda addressed. One of them is that the engine doesn't have "traditional" EGR; that is, it does not route exhaust down the intake. Traditional EGR in a direct-injection engine can be trouble because that exhaust + oil vapor from the PCV (which is mandatory on modern vehicles; you cannot exhaust that vapor to the atmosphere) results in material that can form deposits. With port injection and TBI it's less of a factor because the fuel washes the intake tract either in part (for port injection) or whole (for TBI.) But for DI engines it does not and running fuel additives or "cleaners" will do nothing as the fuel never gets into that part of the engine at all.

But Mazda doesn't use traditional EGR; they obtain the same result by manipulating valve timing. Therefore there is no exhaust stream in the intake mixing with PCV oil vapor.

(If you want to see a truly degenerate case of this pull in the intake on a number of DI diesels, such as the ALH engine VWs.... diesel fuel of course produces much more soot than does gas but the issue is the same.)

Second, while the oil vapor IS present Mazda identified the thermal regime that leads to coking of that vapor and appears to have gone a long way toward eliminating it.

But third, even without that mitigation it's only a factor when build-up in the intake results in either hanging valves (which can lead to mechanical damage via piston impact) or compromised sealing. I challenge you to find such an example on the SkyActiv engines, as I've yet to see it documented thus far. These engines have been out there long enough at this point that if it was going to happen there would be reports complete with photographic proof and destroyed cylinder heads by now. And by the way, I have over 180,000 miles on mine. I've seen ONE photographic claim and I'm calling BS on there not being something wrong with that specific engine (or the "evidence" being doctored), as with as many miles as I have, and what was in THAT set of images and claimed mileage I'd long ago had hung up every one of my intake valves and destroyed at least the cylinder head if not the engine as a whole.

The SkyActiv engines are interesting animals in that they attempt to blend Miller/Atkinson/Otto cycle operation. It's how they get both good performance and higher fuel economy. But that higher volumetric efficiency can only be maintained in certain parts of the operating envelope and it is detecting the edges and the cam phase changes that come when the ECU switches between them that results in a slight loss of smoothness during that transition. Remaining in that transition area on purpose is silly, much as is lugging any engine, except that remaining where the ECU is toggling back and forth (unlike lugging) is probably not going to hurt anything -- it just isn't great from a smoothness of operation standpoint -- and the ECU wants to be in that higher volumetric efficiency range of operation if it can because that's how you get the better fuel economy.

Never mind that a cycling A/C compressor, ESPECIALLY when it's hot out and the head pressures are high on a car that requires quite a LOW amount of horsepower to move it at a given speed is going to be VERY noticeable in terms of smoothness.

If you're accelerating moderately and demanding 100HP out of the engine and the A/C clutches in and wants 5HP, you're not going to notice very much. If you're in the low-RPM, low-output part of the operating envelope at 25mph and your net engine output is closer to 10HP (in other words you could use a lawn mower engine to move the car at that speed) that same 5HP is now HALF of the engine's output and the instantaneous load change, until the ECU can compensate for it, is quite noticeable. It's made worse by lighter engine reciprocating and rotating mass because there's less momentum available for the instantaneous demand when the clutch on the compressor engages. All other things being equal a 4-cylinder will show much more of this "hiccup" than will an 8-cylinder simply because the moving parts of the 4 cylinder mass less.

In days of old with carbs when the A/C clutched in there was a solenoid mounted at the throttle lever that was also engaged and cracked the throttle lever slightly off-idle because without that the engine might actually stall. Now with everything being drive-by-wire it's all electronic but the principle is the same -- the ECU has to compensate for the instantaneous load change when the A/C is clutched in, and at low power output levels you definitely can feel it as a slight hesitation. It's normal.

Eliminating A/C as the cause is easy -- turn it off completely and see if the hesitation disappears. If so there's your culprit but there's nothing to do be done about it since the design of the A/C systems on these vehicles, along with most other US and Japanese models, are clutched-compressor systems instead of variable-displacement. Variable-displacement systems (VW/Audi and many other European makes use this design) don't display this behavior.

FWIW I can notice the A/C clutching hesitation during low-RPM loaded operation on my "6". It's normal if the A/C is turned on and since I live in Florida it usually is.
 

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When I got my 08 Mazda 6 it was having a similar problem. You could have a faulty spark plug or coil. When I replaced all 6 plugs and 6 coils that hesitating went away instantly.
 

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I get more jerking in my 3 at low RPM with the AC on, usually right after start up when its cold. What gear/rpm are you in when this happens?
Hi, I have a 2018 6 Touring. Yes I have the same issue and Mechanic plus regional engineering say that the car and codes are all normal and operating as designed. The way I read their response is that all cars are designed with this low speed stutter/hesitation and this is normal. But i read that there is an A/C interaction that may cause the problems. Well, I live in Arizona and the A/C is a constant companion where driving is concerned. Know I hear this is common, and know Mazda is not interested in correcting this anomaly, I have a plan to resolve the issue that does not involve Mazda. BTW; just had the recall PCM update. It did nothing except stop the crazy car slow-down when i accelerate from low speed.
 

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There's nothing you can do unless you intend to retrofit the A/C with a RCV-based compressor, which is not impossible -- but takes some care and engineering, since the car wasn't designed for it.
 

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I don’t recall if you said how many miles the engine has on it, but I was experiencing the same issue with hesitation when accelerating from a stop or while cruising under 2000 rpm. I thought that the issue might be the plugs but whe I checked my air filter it was filthy. I had gone 20,000 miles with the filter.

I replaced it with a new one and the hesitation was gone. No new plugs, no high octane fuel, just regular maintenance.

I would start with the simple things. Air filter first then check the plugs. Plug life and engine mileage are not mutually exclusive.

When you eliminate the impossible, whatever remains, however improbable must be the truth. - Sir Arthur Conan Doyle (Sherlock Holmes)
 
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