Strange 2.5T Engine misfire problem w/multiple choice answer game. Come play.

[Tchman2016]

I eventually started getting codes but it took several months. Codes usually happened in parking lots when I was backing in/out of a spot or other slow maneuvers.

Mazda and my dealer were helpful through the process.

I believe it was only a single cylinder misfiring. Not all of them.

Basically if car was in gear and I’d put the ebrake on and let off the foot brake so there was some load on the engine. You could feel it was running rough and idle would dip down below 500rpm.

Daily driving on the highway you’d never know..it was slow speeds or at a stop where it felt off.

Ahhh! Yes exactly it, you'd never know during normal driving which is crazy. Only doing the standstill idling in drive with foot on brake or slow maneuvers is when it strikes and those exact symptoms show.

I just don't want to drive the car around hoping a code will store or cel pop on dash and do more damage to the cats.

The flip side is the dealer may say well there isnt a code and the money light is not on so come back when it does, all the while having a horrible running engine that they can see but wanting me to go away and do more damage, rather than investigating on their dime. It's ridiculous and manufacturers just hate paying for stuff.

 

[GTEyes]

Ahhh! Yes exactly it, you'd never know during normal driving which is crazy. Only doing the standstill idling in drive with foot on brake or slow maneuvers is when it strikes and those exact symptoms show.

I just don't want to drive the car around hoping a code will store or cel pop on dash and do more damage to the cats.

The flip side is the dealer may say well there isnt a code and the money light is not on so come back when it does, all the while having a horrible running engine that they can see but wanting me to go away and do more damage, rather than investigating on their dime. It's ridiculous and manufacturers just hate paying for stuff.

You could simply pay them to do a compression test. if that is indeed the culprit, that will identify it and give them what they need to open a case with Mazda.

 

[Tchman2016]

You raaang?

I've actually been watching this thread to see what the solution was and to offer help where possible. Unfortunately I've never run into this problem, and I've never seen any other reports on the forum about this. I was planning to try checking idle RPMs in Drive to check for idle changes on and off the brakes, but it looks like that's already been tested and confirmed by others as normal (outside of the misfiring).

@Tchman2016 I'd check the fine print of your extended warranty to make sure you follow the process outlined in making a warranty claim. Sometimes there are disclaimers saying you need to have a diagnosis performed by "X" dealer before the claim can proceed, so it would be a waste to take it to "Y" shop, have it diagnosed there, and then try to file a claim and have it rejected just because you didn't go to the "X" dealer for diagnosis.

If it were me, I'd put the original plugs back in (in the same cylinders if possible) before taking it to the dealer for diagnosis. When they run through their troubleshooting, the plug condition would likely help them figure out the underlying cause.

Haha the all knowledgeable sm1ke has entered the chat! You're a good man thank you.(Actually everyone here is)

Yes, i'm going to do exactly that, put the original plugs back in the same cylinders ( I kept them in order) and make a dealer appt.

The warranty is Mazda OEM Platinum exclusionary with no deductible. So that's a huge plus if they come through.

I'm wondering if I should suggest to the dealer that they boroscope and run a compression test on all cylinders as well as a leakdown test and offer to pay for those services out of pocket as a gesture of faith they will want to try hard to find the issue and not have to depend on warranty diagnostic and rush. What do you suggest?

 

[Silly Wabbit]

If you want I can send you my old set of oem plugs w/ 35k miles. That way you have oem equipment when you bring it in.

 

[Tchman2016]

If you want I can send you my old set of oem plugs w/ 35k miles. That way you have oem equipment when you bring it in.

No way!!!! That is so incredibly generous of you my jaw dropped i'm speechless.

That would so awesome and I can feel so much easier knowing they can't try to blame something on my own plugs. I've played that game before and it's so much aggrevation.

Really, THANK YOU and I will be happy to pay you something for them and of course shipping.

You all rock and I'm so happy to be a part of this community to help when I can as well and feel good that we've all got each other.

I'll send you my address and send me your PayPal or zelle email!

 

[sm1ke]

Haha the all knowledgeable sm1ke has entered the chat! You're a good man thank you.(Actually everyone here is)

Yes, i'm going to do exactly that, put the original plugs back in the same cylinders ( I kept them in order) and make a dealer appt.

The warranty is Mazda OEM Platinum exclusionary with no deductible. So that's a huge plus if they come through.

I'm wondering if I should suggest to the dealer that they boroscope and run a compression test on all cylinders as well as a leakdown test and offer to pay for those services out of pocket as a gesture of faith they will want to try hard to find the issue and not have to depend on warranty diagnostic and rush. What do you suggest?

Lol I'm only as knowledgeable as the community, everything I learned comes from you guys

I think I would trust the process and raise your concerns with the dealer. Have them verify the symptoms and see what they do next. If they try to send you away, explain your concerns about potentially causing additional damage and the uncertainty of having to drive the car in that state, not knowing what could happen and how badly it could damage the car by continuing to drive it. Maybe loop the service manager in at some point in the convo so they're aware of your concerns. Hopefully that's good enough to give you a loaner so they can do a deep dive on the car. And if it's not, and they insist on waiting for things to get worse, consider running it up the chain to Mazda Corporate.

It's hard to say what the best course of action is.. In my experience, the service reps at the desk are service salespeople - they don't actually service the cars, they act as middle men between the customer and the mechanics doing the diagnosis. Which means that talking to them about what you've done and potential further testing could be wasted breath, especially if they simply want to follow their internal policies and wait for check engine lights or whatever.

On the other hand, there are some service reps that have a mechanical background and would be able to discuss the troubleshooting path and diagnosis with you. Those reps are usually more sympathetic and are more open to running those tests, especially if you're offering to pay for them to speed up the repair process and get your car back to 100%.

 

[Z31]

Wonder if it would be worth having a look at the cylinder and valves with a boroscope while changing the plugs. I think you can get them fairly cheap now on Amazon.

Might not be worth it if you can go back to dealer and still in warranty, etc.

 

[Tchman2016]

Hey guys,

Just an update. I received the plugs that Silly Wabbit graciously sent. @ SillyWabbit Thank you again that was incredibly nice of you!

It's been raining and I haven't had time to install them but i'm going to asap.

In the meantime, I ordered a higher end scantool that graphs live data and to see if there would be any difference between what I have already and received it today. I hooked it up and noticed an anomaly on the o2 sensor data. There are two o2 sensors and I noticed one very erratic and the other one doing almost nothing. I don't think that's right, however there are zero codes for anything wrong. Here's a pic taken with the engine at operating temp in closed loop.

Anyone know what to nake of this?

Also, the engine misfire counts are all over the place for each cylinder, meaning sometimes is only a handful for only 1 cylinder during a trip and other times its a handful for each cylinder during a trip or just a couple cylinders. Its so bizarre.

Anyway, I'm wondering if there is an oxygen sensor issue now. I'd like to do my own cylinder compression test when I have the plugs out again so i'm going to order one from Amazon for like $35. Some innova one I saw in advance auto. I believe a good pressure should be between 140 and 160 PSI per cylinder with no more than 10 percent variance between cylinders. Someone correct me if i'm wrong.

Thanks all

 

[GTEyes]

Hey guys,

Just an update. I received the plugs that Silly Wabbit graciously sent. @ SillyWabbit Thank you again that was incredibly nice of you!

It's been raining and I haven't had time to install them but i'm going to asap.

In the meantime, I ordered a higher end scantool that graphs live data and to see if there would be any difference between what I have already and received it today. I hooked it up and noticed an anomaly on the o2 sensor data. There are two o2 sensors and I noticed one very erratic and the other one doing almost nothing. I don't think that's right, however there are zero codes for anything wrong. Here's a pic taken with the engine at operating temp in closed loop.

Anyone know what to nake of this?

Also, the engine misfire counts are all over the place for each cylinder, meaning sometimes is only a handful for only 1 cylinder during a trip and other times its a handful for each cylinder during a trip or just a couple cylinders. Its so bizarre.

Anyway, I'm wondering if there is an oxygen sensor issue now. I'd like to do my own cylinder compression test when I have the plugs out again so i'm going to order one from Amazon for like $35. Some innova one I saw in advance auto. I believe a good pressure should be between 140 and 160 PSI per cylinder with no more than 10 percent variance between cylinders. Someone correct me if i'm wrong.

Thanks all

I think you're slowly uncovering some clues but it might be the best to get the car to a professional to look at it. You don't want to do more damage here.

 

[roundle1979]

Following with interest.

Erratic O2 sensor readings could also be due to an erratic 'up stream' issue as well.

 

[mpilon]

Oh I forgot to mention that I measured the plug gap on all 4 plugs today after pulling them out and I found the gap to be .27 on all of them which I though was unusual because the spec for the engine is .30.

So, the fact that the plug smells like gas and looks sooted up would mean its not firing correctly right? Injector leaking into the cylinder or bad coil? Coolant intrusion dilution causing a no ignition?

I'm wondering if I should buy some new plugs at the dealer and check the gap and install and see what happens misfire wise but I need to pressure test the cooling system first. 2 parts stores gave me loaner tester and both did not have the correct adapters for the radiator neck. So frustrating.

Fuel injector?
Since all cylinders are showing misfires I'd consider a more global issue; in no particular order :

1) fuel pump, pressure regulator?
2) try a can of BG-44K in a fresh tank of gas - if that changes things for the better, go down the fuel rabbit hole.
3) check ECU wire harnesses, connectors only partially plugged... Injector and coil connectors esp.
4) since plug #3 was wet, try a new fuel injector; if you don't want to buy a new one for the test, swap #3 with another and see if the #3 is dry, the other wet...

I'd do #4 first.

mmmv,
M.

 

[SparkYellow]

Following to learn.

With the new device do your ambient/intake temps appear normal?