Sputtering problem

[rh71]

2002 Mazda MPV minivan @ 120k miles. Maybe sputtering isn't the right word and not sure what a transmission slippage feels like but it feels like either a transmission or fuel delivery issue. Only between 40-55mph while accelerating (not coasting) and around the 1500-2000 rpm mark (but never at exactly the same RPM), we feel the car slightly jolt for half a second before continuing to accelerate. It's not just a lurch forward but more like back and forth gently. Very easy to replicate on a highway while accelerating slowly while in traffic between the above speeds. The transmission shifts or RPM were never very distinct so it's tough to tell if it's trying to shift at that moment.

One thing to add is that it had been happening for weeks and then finally the CEL comes on. Code indicated fuel/air mixture ratio issue and it was brought into the mechanic. They fixed some hose and now the CEL light is gone but they never felt the sputter and so the issue remains. In the past in a Honda Accord we had an O2 sensor issue where giving it gas does nothing for accelerating, but this feels a bit different than that. Don't believe the spark plugs have been looked at recently.

 

[bradly1101]

It could be a few things. I had an older car that sputtered a bit a idle, wasn't a big deal to me until it didn't pass a smog check. The trusted mechanic told me that the EGR system needed "scrubbing." After that all was well. But yours sounds like more of a drivetrain issue, possibly transmission. Have you changed its fluid?

 

[rh71]

It could be a few things. I had an older car that sputtered a bit a idle, wasn't a big deal to me until it didn't pass a smog check. The trusted mechanic told me that the EGR system needed "scrubbing." After that all was well. But yours sounds like more of a drivetrain issue, possibly transmission. Have you changed its fluid?

No don't think the ATF has been touched and the manual doesn't indicate it should be at a certain interval. Reading that it should be left alone unless it smells burned or changes color.

 

[bradly1101]

No don't think the ATF has been touched and the manual doesn't indicate it should be at a certain interval. Reading that it should be left alone unless it smells burned or changes color.

Remote diagnoses are so difficult...

 

[mindless1]

Once upon a time ago I had a (different vehicle entirely) doing this sort of lurching gear change when a vac line had popped off the transmission housing. That may not be it but it seems like a tranny issue to me.

However you could hook up an OBDII dongle to stream live data to a phone or tablet to see the engine operation parameters, if nothing else to see if the fuel trim (rich/lean mix) is within the right values or it's trying to overcompensate for a vac leak still.

However if you're inclined to get a mechanic to fix it and it's very easy to replicate, just tell him what you told us. Is it possible the engine has to be warmed up for it to happen and the mechanic was driving it cold?

 

[C1]

What is being described sounds like a slightly sticking lock-up torque converter (not unlocking smoothly). Typically the lock up is around 40-45 mph.

Check to see if it happens when the auto lock-up is "off".

And BTW, get a full professional service on your transmission. You've probably already fouled the tranny by not getting regular fluid & filter changes. (Where do you think band/clutch material and particles go when you dont regularly replace the fluid ? That's right, it ends up clogging the valve body and oil channels resulting in rough/erratic shifting and ultimate transmission failure which probably what is happening now. 100K to 120K life is just about what I would expect from a tranny that was never properly serviced/maintained.)

 

[mindless1]

^ 100K+ is now the proper service interval for trans fluid, unless it's a defective design like some still use. We could debate the new era "sealed for life" no service ever trend, which is obviously false, but it's generally untrue to claim a tranny wasn't properly serviced or maintained once vehicles shifted to using HQ synthetic fluid meant to last 100K mi or more. It's a design problem not an owner fault if one fails in this mileage range with original fluid.

 

[C1]

That's right, 100K is the new service interval for a tranny. As West Auto Group will attest to you, with the new standard, around 100K you will get new oil - with your "new transmission" !

https://westautomotivegroup.com/5-tips-tricks-to-keep-your-cars-transmission-healthy

The whole synthetic thing (WS or World Standard specification) oils is part of Agenda 21/2013 and is environmentally driven/based.

 

[mindless1]

^ I was really referring to older vehicles, 100K mi was the service interval 20 years ago, now many use a "lifetime" fluid change interval. This tells us that past 100K mi they saw few enough failures to do away with that limit. Most vehicles find their way to a junkyard without ever having a tranny replacement, are worth so little at that point to make it not cost effective if it did fail, meaning well past 100K, usually 200K mi.

Granted that does not mean some don't need it more often which is why the owners manual usually stipulates this interval, and some are driven harder, used to tow or carry more of a load, higher ambient temperatures and hills, etc.

Synthetic increases lifespan by increasing the thermal breakdown temperature as well as better cold flow.

There is no question in my mind that a shop that does transmission flushes will recommend one as often as they can make the customer believe it's "needed". Find an owners forum and see what their tranny failure rates are like. If it is prone to failure, sure there's a special case where I would change the fluid more often.