Ongoing misfire/stuttering problem after many parts replaced, need help!

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2010 Mazdaspeed3
Hi all. I'm new here. I inherited my husband's 2010 Mazdaspeed3 last year to be my winter driver. It has about 98,xxx miles and he babied it the whole time he drove it. Was his dd for years. He said it's always had a very mild stutter in the acceleration at certain RPMs, and he mentioned it to the dealer when he first bought it but they never found anything wrong. Well, it seems to have gotten worse. We've spent tons at the dealer, they had it three separate times. The last time I was certain it would be fixed (they replaced the EGR) but the misfire came back a few weeks later. We can't spend any more money on this car but I want this fixed. I hope to drive it another 100,000 miles. :) So I'm hoping you guys can help.

I did a bunch of searching and found lots of threads on misfires and stuttering, but each one is a little different and most said the EGR was the issue. Well, not here.

Here's what happens:
At completely random times, when I hit the gas, not crazy hard, but hard enough to push the engine a little, sometimes it will stutter or slip. Sometimes a little, sometimes hard enough to jerk the car a little. I'm pretty sure this always happens before the turbo kicks in. It's almost like I've caught the car off guard and it stumbles before it moves. After one or maybe two slips, full power will kick back in and it's all good. At first it seemed worse on rainy days. I learned to expect a few stutters on my commute. But sometimes it happens on dry days too. It could be my imagination but it also seems worse when the tank is at 3/4 or lower.

Here's what we've had done:
visit 1: computer update
visit 2: replaced spark plugs, coils, fuel injectors
visit 3: EGR

The dealer mentioned that the engine has a lot of carbon build-up. They suggested fuel additives. They said everything passed the final diagnostic they did. The EGR was failing tests which is why they replaced it. Everything else passes now. When they drive it, they never feel the misfire. But every time I brought it in there were misfires logged so they knew I wasn't making it all up. :)

Weeks went by after the EGR was replaced with no misfires. But now they are back.

My husband is going to clean the mass air flow sensor and see what happens. I think we're also going to try some fuel additives but we both think that's such a weird fix for something like this. It can't really be that simple.

What do you guys think?
 
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Speed3
I don't think that it would be the carbon build up. I've had plenty of vehicles that've had carbon buildup and usually it's just overall reduced power. Unless you can get a boreoscope in there, I'd look elsewhere.
 

Preferio

I break stuff.
Contributor
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2003 Mazdaspeed Protege 1660, 2004 Winning Blue RX8, 2005 Mazda6
Do we KNOW it's a misfire?

Are there any DTC's stored?

If so, which ones?

Compression test or leakdown test performed?

View live misfire monitor to identify what cylinder is misfiring?

What test did they perform to determine the EGR was the culprit?

Any freeze-frame data to be had if there are stored DTCs?
 
Its interesting that EGR service corrected the problem for several weeks but the issue has now returned.

A couple thoughts:

What fuel are you using? It must be premium, 91 octane or higher, preferably 93 if available.

Could there be any contamination of fuel - water, etc.? Try a different gas station.

What has changed since the EGR service?
 
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2010 Mazdaspeed3
Do we KNOW it's a misfire?
Are there any DTC's stored?
If so, which ones?
Compression test or leakdown test performed?
View live misfire monitor to identify what cylinder is misfiring?
What test did they perform to determine the EGR was the culprit?
Any freeze-frame data to be had if there are stored DTCs?

Yes, it had logged misfires in the last 10 drives every time I brought it in. There were a ton at first, but less were logged as parts were replaced.
I'm sorry I don't know what DTCs are. No compression or leakdown test as far as I know. They told me they specifically put the EGR through tests and it was failing every one. I don't specifically know what. :/ That's what led us to replace the EGR. And I don't know anything about freeze-frame data. Sorry I know that's not very helpful.


Its interesting that EGR service corrected the problem for several weeks but the issue has now returned.
A couple thoughts:
What fuel are you using? It must be premium, 91 octane or higher, preferably 93 if available.
Could there be any contamination of fuel - water, etc.? Try a different gas station.
What has changed since the EGR service?

This car has always had premium, 93 octane only. I did worry about bad gas and switched gas stations, but there was no change, it was still misfiring. Nothing changed after the EGR was replaced. It drove great for weeks, leading me think it was finally fixed. Then it went back to the same stuttering it was doing before.

Here's something to ponder though. This car has been garaged since it was new. Then my husband got his new car, and with the new car and my 370Z in the garage, the MS3 got kicked out to the driveway. Does it collect moisture more overnight since it's outside? Who knows. The misfires always seemed worse on wet days.

And here's another thing. My husband cleaned out the Mass Air Flow sensor this weekend. I drove it Monday and today. No misfires. And I really pushed it. I'm not getting my hopes up because it's done this before where it improves then goes back to the stuttering. But what if? Would the dealer seriously miss that, and charge us thousands to replace other stuff when it was that all along? That's kind of hard for me to believe...
 

Preferio

I break stuff.
Contributor
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2003 Mazdaspeed Protege 1660, 2004 Winning Blue RX8, 2005 Mazda6
DTC- Diagnostic Trouble Code

Freeze frame will show PIDs like engine speed, temperature, vehicle speed, intake temperature, fuel trims, etc. When the problem occurs. Its information that's stored in addition to a DTC and is the IMPORTANT information.


I ran independent shops for 9 years and have been at a dealership for three years. Dealerships aren't the knowledgeable shrines of OEM repair people think they are. I've been at both. That's why I always recommend people locate an independent shop in their area that specializes.

With that being said, it doesn't surprise me that a dealership service department didn't view FF data, take logs or seek technical assistance from Mazda of North America. MAF issues are easily identified by any decent technician, especially with your complaint. Monitor your concern and report back.

Sent from my LG-E980 using Tapatalk
 

hornsfan10609

Certified Mazda Tech
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2003.5 Mazdaspeed Protege x2
If you live in a decent sized city there should be at least one decent tech at the Mazda dealer. But Preferio is absolutely right, there were some complete morons in the shop when I worked at Mazda and I worked at the third largest dealer in the US. It is more than possible they didn't bother or know how to diagnose the problem. Reading your post my first thoughts were bad gas or a dirty MAF sensor. Does the car have a K&N filter or an aftermarket intake?
 
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2010 Mazdaspeed3
If you live in a decent sized city there should be at least one decent tech at the Mazda dealer. But Preferio is absolutely right, there were some complete morons in the shop when I worked at Mazda and I worked at the third largest dealer in the US. It is more than possible they didn't bother or know how to diagnose the problem. Reading your post my first thoughts were bad gas or a dirty MAF sensor. Does the car have a K&N filter or an aftermarket intake?

We're actually driving to the farther dealer because our close one let us down about something else. There's a third dealer we could try, but sheesh, ya know? They're just making this too hard! And nope, no K&N or aftermarket anything. The whole car is all stock.
 

hornsfan10609

Certified Mazda Tech
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2003.5 Mazdaspeed Protege x2
I think you will be fine with the cleaned MAF sensor, especially if you have already done the plugs, coils, injectors and EGR. As long as the plugs are gapped correctly the car should run fine.
 
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2010 Mazdaspeed3
It's been driving great since my husband cleaned out the mass air sensor. I'm still waiting for the misfires to return, because after every previous fix it went weeks driving great then back to misfires. Maybe they won't return? Maybe we spent all that money when it was that sensor all along? (gah)
 

Preferio

I break stuff.
Contributor
:
2003 Mazdaspeed Protege 1660, 2004 Winning Blue RX8, 2005 Mazda6
It's been driving great since my husband cleaned out the mass air sensor. I'm still waiting for the misfires to return, because after every previous fix it went weeks driving great then back to misfires. Maybe they won't return? Maybe we spent all that money when it was that sensor all along? (gah)

Just as another follow-up? How is the car doing?
 
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2010 Mazdaspeed3
It's doing great. No issues. It still drives like a beast after he cleaned out that mass air flow sensor. But it makes me wonder, what causes a mass air flow sensor to get dirty? Is this a normal maintenance thing we need to have cleaned out regularly? Or is this an indication of something else wrong, like the air filter not doing a good enough job?
 
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