RPM drops, occasional DSC light on (2014 Mazda5)

[Lazy2.5]

Is there anything wildly abnormal, that should further be investigated?

No.

 

[Silentnoise713]

I will also look into installing the inline filter. Doesn't look too hard so far.

Not hard but IIRC you need to remove TB, air filter box, battery box to have full working access if you want to intercept it before the cooler. BUT I think you can just work from the bottom IF you intercept the flow AFTER it comes out of the cooler. TIP, buy a foot or two of transmission hose from auto store (its cheap). Save the OEM 'pre-bent' hose b/c they cost an asinine amount, in case you want to reuse it.

From what I observed over a brief drive monitoring session, it does engage/disengage as supposed to - see the OSS graph (orange). The big flat space between 100 and 128 is idling at a stop.

Is there anything wildly abnormal, that should further be investigated in your opinion?
I would greatly appreciate any advice on which parameters to group on this graph that would help to understand what is going on.

Also, I tried feeding this data into chatgpt4o and, to my surprise, it outputs something that now actually makes sense, although, the recommendations are very generic, i.e., "note whether a change in LPSA LPSB correlates with gear shift, look for random spikes on OSS, etc".

Million dollar question: does FORScan have a TCC override function to lock or unlock the clutch on demand? The idea is to see when RPM drops, does clutch slippage occur? At stop (when low idle occurs), can you manually override the clutch to lock it?

Does this occur for you when the car is cold? Assuming you are experiencing the situation I suspect, it does not b/c the clutch stays locked (no vibration) to help warm it up (IIRC for emission). What I'd like to know is, when the car is warm/hot, does locking the clutch make it go away?

See vid below for ref. Different issue but monitoring use case would be very similar.

FORD ESCAPE RPM SURGE

2017 Ford Escape has rpm fluctuation while driving steady between 25-40mph on flat or slightly inclined road. This vehicle was fixed & surge is now gone.

www.youtube.com

 

[hleboklop]

Seems like some control of the transmission solenoids is available. Buttons are inactive because currently the car is not connected.
For the record, this is an activated version of FORSCan on PC with vLinker OBD2 cable.

I'm now doing the research on which one controls the clutch.

And when I figure this out, the plan is:
1. drive until warmed up, monitor the TCM
2. stop in D, wait till RPM drops below 600 (~590..605 in my case) and vibration occurs
3. activate the clutch solenoid and see if the vibration goes away

If the vibration goes away - the torque converter is to blame,
if not - then something else.

Am I getting this right?

 

[Silentnoise713]

Seems like some control of the transmission solenoids is available. Buttons are inactive because currently the car is not connected.
For the record, this is an activated version of FORSCan on PC with vLinker OBD2 cable.

I'm now doing the research on which one controls the clutch.

And when I figure this out, the plan is:
1. drive until warmed up, monitor the TCM
2. stop in D, wait till RPM drops below 600 (~590..605 in my case) and vibration occurs
3. activate the clutch solenoid and see if the vibration goes away

If the vibration goes away - the torque converter is to blame,
if not - then something else.

Am I getting this right?

That is the idea!

Pic of solenoids that match up to the FORScan menu/options.
I didn't realized there's a secondary valve body with a different "Pressure control solenoid B"!

Mazda FS5A-EL Valve Body 2005-UP

worldwidespecialtyparts.com

 

[Lazy2.5]

If the vibration goes away - the torque converter is to blame,
if not - then something else.

With all due respect sir, I do believe you are overthinking, whatever is going on with your vehicle.

As I've mentioned, the first step is to ensure the bottom of your pan, magnet, filter is all clean.

This should significantly help with the torque converter drag and vibration you are experiencing.

If you are still unhappy with your transmissions performance, next step would be to refresh your valve body and solenoids.

So, very excessive and high vibration in drive is not a good sign of transmission health, it's probably the torque converter, although not necessarily.

The original 6 speed auto in my car (under my username) has more than 300,000km on it. Aside from 4 pan drops and one drain/fill, nothing else has ever been done to it. It shifts flawlessly across the entire rev range. Vibration is of course existent, but minimal.

Under most scenarios, I'd expect your transmission to also last a long and healthy life - as long as you are regularly dropping the pan for servicing. At 80k miles, just a drain and fill is not enough.

 

[hleboklop]

UPDATE

Earlier:
I had some issue with RPM drop and stay low when rolling -- to address this, I cleaned the throttle body and MAF sensor. This fixed this issue.

Later, I started noticing vibration in D when stopped. I decided to not follow the advice posted in this thread, and I didn't play with clutch engage via obd2.

Recently, I went to dealership, and paid $300 for diagnostics.
At the dealership, the technician found stored code P0661. According to the logs/freeze frame, this code appeared right after I decided to give up trying to figure out what was wrong with that vibration. This code didn't trigger the check engine light or other lights.
As per technician report, one solenoid was stuck in open position, and I guess, the other one was kind of failing.

So, I replaced the solenoid valve LF82-18-740 and cleared the code.
Here's a great video guide on this fix:

The vibration in D when stopped is gone, well, almost gone.
Now, if I stop in D, the rpm might occasionally drop to 600 and below, the vibration happens, but then the engine adjusts the rpm to 620-660, where there's no vibration.
Previously, it would just drop flat to 600 and vibrate.
I guess, it will take some more time for ECM to relearn. Normal RPM idle when no abnormal vibration is noticeable is around 650, I think.

I'll update this thread with MPG observation later, but overall, I consider this issue as resolved.