Mazda 6 Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Ah crap. My transmission is doing something hard to explain. At least, I feel like it's the trans.

2014 6 touring with AT and 120,000.
trans filter/fluid change at 75,000 (planned on keeping it for another 5+ years)
I'm not a grandpa driver. A lot of stop and go in Chicago and I have a semi-serious road rage condition. Self diagnosed, of course...

symptoms:
When I accelerate, and the car downshifts automatically and it jerks/thumps. It's very sporadic and if I baby it, no problem. By baby, I mean take 20-30 seconds to get up to 60 MPH and no heavy acceleration. Sometimes I can accelerate WOT from a stop and it's no problem. Other times WOT acceleration results in the thump/clunk and then the car goes into low power mode and the check engine and traction control lights come on. The dummy lights stay on until I stop the car and turn it off. At which time I start the car and resume driving as normal, albeit much more gently.

I'm carrying my fault code reader with me in hopes that i get a convenient opportunity to pull the trouble codes but the few times they have come on, I haven't been in a situation where it was safe to stop for a period time and fumble with the code reader. Even though I changed my fluid and filter at 75k, I'm going to do it again Saturday. I'll also change plugs, air and oil/filters, etc. if I'm working on the car, I'll do everything. If, after I change everything, it still continues, I'll force it into giving the code. The symptoms are getting more frequent so if filter/fluid change doesn't work, reading the codes shouldn't be a problem. I did check the fluid level and it was spot on.

I hope I'm missing something easy here and someone reads this and the light bulb goes off but if that's not the case, has anyone replaced their transmission by themselves? Have you done it by pulling the engine out of the top? I have the equipment to do that, but I don't have a hoist so I can't lift the car up off the engine. If it is a bad trans, I would want to buy a used one off ebay and swap.

As always, I appreciate all of your input. i don't post often but i do get a lot of valuable from the community so thanks in advance.
 

·
Registered
Joined
·
2,987 Posts
In virtually every case you want to drop the gearbox SEPARATE from the engine, and out the bottom.

You don't need a hoist -- some good jackstands with enough height will do, plus an engine support bar (you have to disconnect the driver-side mount, so the bar is to hold the engine up while the gearbox is being R&Rd) and transmission jack (or another floor jack, but that's somewhat of a high-wire act balance-wise.)

Same deal with a MTX clutch job, basically. The fun part is that clearances are usually not plentiful by any stretch of the imagination. Note the "must replace" bolts involved (typically the mounts and sometimes the half-shaft flange bolts.)

Pretty good odds this is a sensor or valve body problem, and may be fixable in the car. Not sure. But if it keeps doing it you'll eventually destroy the clutches and then it's gearbox time.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #3
Thanks Ticker.
I wonder if it would be worth it to throw an extra 75$ and put a refurb valve body in since I'll have the pan off anyway.

ebay refurb valve body

Personally, I think it's a small price to pay given I'll have the cover off anyway...
 

·
Registered
Joined
·
2,987 Posts
I hate throwing parts at things; replacing perfectly good parts is both expensive and brings about quite a bit of risk of you screwing something up while doing it.
 

·
Registered
2015 Mazda 6 Sport
Joined
·
602 Posts
I hate throwing parts at things; replacing perfectly good parts is both expensive and brings about quite a bit of risk of you screwing something up while doing it.
Also, changing multiple parts at once makes it way harder to figure out what the problem was. I think it's best to go one step at a time when it comes to doing repairs, but that's personal preference.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #6
Agreed. I'm not going to throw parts at it. There's too many unknowns.

24hr update:
Ride to work this morning was no problem. Babied it the whole way.
Ride home i manually shifted the whole ride and had a couple opportunities for testing. Manually shifting, I had no problems. Interestingly enough, cruising at 65 in 6th gear, I went WOT and I felt what seemed like a slip or a missfire. It was a quick small hesitation. Lots of directions this could go.

I have to work a half day tomorrow and then will drive it until I can get the error code to pop up. It's my only hope at this point. I really can't not drive it as it's my only vehicle and I'm not interested in taking it to the stealership at this point. I've got a call in to the local independent mechanic who carries a pretty good reputation.

I'll keep posting updates in hopes that this helps someone down the road.

Thanks,
 

·
Registered
2015 Mazda 6 Sport
Joined
·
602 Posts
Agreed. I'm not going to throw parts at it. There's too many unknowns.

24hr update:
Ride to work this morning was no problem. Babied it the whole way.
Ride home i manually shifted the whole ride and had a couple opportunities for testing. Manually shifting, I had no problems. Interestingly enough, cruising at 65 in 6th gear, I went WOT and I felt what seemed like a slip or a missfire. It was a quick small hesitation. Lots of directions this could go.

I have to work a half day tomorrow and then will drive it until I can get the error code to pop up. It's my only hope at this point. I really can't not drive it as it's my only vehicle and I'm not interested in taking it to the stealership at this point. I've got a call in to the local independent mechanic who carries a pretty good reputation.

I'll keep posting updates in hopes that this helps someone down the road.

Thanks,
I hope the best for your findings and I'm curious to know what the problem is so keep us update :)
 

·
Registered
Joined
·
2,987 Posts
I'd bet on an intermittent sensor or solenoid... probably not all that hard to fix once you know where the problem lies. The difficulty is in figuring that out before critical damage is done to internal parts.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #10
Yes. Over the last couple days, I've been driving the car up shifting manually. I will now classify this as a hesitation and it will happen in any gear and anytime I'm accelerating with the throttle beyond 1/2. +/-.

I invested in a bluedriver OBD scan tool and I'm glad I did. I have an Autel but bluedriver is so much more. I wasn't ever able to pull up pending codes with the Autel.

bluedriver pulled a pending transmission code: u0442-00 - Invalid data received from ecm/pcm 'b'. although there isn't a lot of info in regards to this specific code, I have an idea and will be digging into it tomorrow.

Earlier this summer, my battery had started leaking. I don't know how long it was leaking. not long. A week or two at most because I check under the hood each time I get gas. It leaked enough that it corroded the hold down strap. i pulled the battery, sprinkled plenty of baking soda and thoroughly washed the engine compartment.

However, I never thoroughly inspected everything underneath the battery compartment so perhaps there's a corrosion issue there.

We will see.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
Normal driving the last two days with some heavy acceleration on the way home today. No issues. I haven't done anything but clear the codes that were there when I installed the bluedriver and (this is a potentially big one) fill my tank.

I have never had the pleasure of getting a bad tank of gas so I don't know that it could cause this kind of problem.

I'll give it a couple more days.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #12
Driving a bit aggressively today and got the whole christmas tree....finally.

All of these were pending codes which means if they don't come up again in the next driving cycle, they get erased.
U0401 - ABS code - invalid data received from ECM/PCM
P0303 - Powertrain code - misfire detected cylinder 3
U0442 - transmission code - invalid data received from ECM/PCM
focusing on P0303 because I could feel the car hesitating and misfiring a little before this and after I cleared the codes as well. Even stopped at a red light. I confirmed the same code without the U codes in the parking lot of O'reilly. Picked up a set of spark plugs since the originals had 120k+ on them. Inspected the coil packs, as much wiring as I could access from the top of the engine, and I installed the coil packs in the opposite cylinders to see if I get an error on another cylinder down the road.

Ran the Mazda test which is to heavily accelerate in 3rd gear from 25-35 and back down to 25. Did that a few times and everything felt fine but I can by no means rule this as solved yet. I'll know more tomorrow but the problem is so intermittent now that I have to wait for the idiot lights to come on and pull the codes without shutting the car off or the pending codes disappear.

if the problem stays on cylinder 3, I'll move on to testing the injectors.

Lastly, which cylinder is #3? I've done a couple searches but haven't been able to quickly find out.

Thanks,
 

·
Registered
Joined
·
858 Posts
Cylinder 3 will be the third-one back from the front-pulley. The "front pulley" is of course on the right-most side of the (transverse-mounted) engine. Right Side and Left Side of the car is, as seen by the driver sitting in the car.
 

·
Registered
Joined
·
2,987 Posts
IMHO with all of that I'd be checking VERY CAREFULLY for electrical (e.g. ground) problems..... the odds of disparate things breaking at the same time is very, very low but electrical gremlins will hose all sorts of "unrelated" things at once.
 

·
Registered
Joined
·
182 Posts
This is an electrical problem, I think. Maybe battery, maybe connection(s). First thing to do is clean and re-tighten battery terminal clamps. Go to grounds from there, then connectors (unless you find an issue somewhere).
 

·
Registered
Joined
·
91 Posts
That herky jerky symptoms you described sound like it could be a bad air flow sensor, I had that problem when upshifting/downshift. My car would randomly stall at idle. I had mine replaced last week when it threw all types of code one being p0300. start by replacing the cheapest parts first : spark plugs, coil packs, then air flow sensor.


Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
10 Posts
Discussion Starter #17
This may be the last post to this thread. The problem hasn't occurred since replacing the spark plugs. Thank you for all of the input and if something comes up again, I'll post here. Unfortunately, I won't ever know if it was a loose connection or a bad plug. All of the plugs ohmed out correctly per the shop manual. Reinstalling the coilpacks after changing the plugs may have solved a loose connection.
 
1 - 17 of 17 Posts
Top