I have a 2007 Ford escape hybrid with 110,000 (original owner) And I am getting sudden shudder/jerk/cut out moments under acceleration… Not hard acceleration but medium throttle at about the time a normal car car would shift gears I experience I experience a sharp jolt... cut out... shudder... it's fairly violent.... and it seems to happen mainly when the vehicle is cold? It somehow feels transmission related? but honestly could be anything?I was wondering if anyone had a similar experience or thoughts on what I could be? appreciate any and all help... its been regularly serviced.. although I believe the trans fluid is original?

 

I was just about to post about a similar issue I’m having, also in a 2007 FEH:

While driving on moderate uphill grades at high speed (60MPH-ish), my Escape occasionally hesitates/jerks in a disconcerting way (I don’t know that I would call it violent, but it definitely doesn’t feel right). When it does this, the engine RPM’s drop slightly and the charge/assist gauge fluctuates wildly, sometimes going deep into the charge zone for a moment. Easing off on the accelerator usually stops this behavior and then after a few minutes it’s fine. I’ve also noticed that this tends to happen when cold although after the warm-up cycle has completed, and more likely to happen after the vehicle hasn’t been driven in a few days.

I’m wondering if this a symptom of typical ICE issues (spark plugs, fuel flow, throttle body, air mass flow sensor, etc.) It’s hard to get a feel for what the ICE is doing behind the eCVT. There are no error codes thrown from these events. Are you getting any error codes?

 

Thanks for your reply… It sounds similar to what I am experiencing… Although mine is a jerk or almost like the engine is cutting out… It's different than when the engine RPMs are changing when I'm going up a hil... Like I can feel the bands in the transmission slipping? I haven't thrown any error codes… Still not sure what it is? Please keep me posted if you find a solution for yours…

 

There are no "bands" or clutches in these transaxles (well, there is ONE..on the first gen. 2005-2008 see below!) No solenoids or valve bodies, either.

This is an eCVT with two electric motors, a planetary gearset, and the final drive. There is nothing to "slip." If there is any jerkiness or shuddering, it is because the power output of the gas engine or the traction and/or generator motor is being interrupted or violently changed for some reason or perhaps - you have a bearing in there that might be seizing up?

The computer controls the output of all three parts - two electric, one gas, to achieve "power balance" with what the driver and conditions are demanding. If you are perceiving a "jerky or shuddering" response, you should be able to track it down to the gas engine or the electric motors using a combination of RPM, watching the gauges, using different power demand, and then something like watching the system carefully in real time with scanning software like FORScan.


Let's begin somewhere: Have you ever changed the fluid in the transaxle? Watch the video to find out why, but:

"Believe me that fluid is breaking down over time with all the heat cycles and is not protecting all those wear areas inside the transmission. In CVT transmissions the most common concern is bearing noise from breaking down because no one changes the fluid in them."


I note something special here: in the video from Prof. Kelly: when he's almost done discussing the HD-10 First Gen., he notes that are a couple of strange things: both a semi-mysterious undocumented one-way sprag (7:00 in the video) AND (much later on in the video) also a mysterious *hydraulic clutch* inside the 1st Gen (2005-2008) at 27:45 which has no apparent oil passages leading to it. Even he does not know why it is there, at one of the final drive output shafts to a wheel! It is not in Gen II (2009-2012) and Gen III (2013-2019).

It is conceivable to me, though, that if you've never changed your fluid and it breaks down or begins to sludge up, that clutch could start dragging and or partially engaging and binding, which might lead to "jerkiness" or "shuddering." Worth a thought if you've never changed the fluid.

 

Finally, finally: Is your car a 4WD model?

 

Let's think about this for a second given the roles of the motor(s) in the transaxle: the regenerative braking ("charge zone" on the dash gauge) feature of this car happens when the smaller of the two motors is commanded by the computer to "pull" rotational and kinetic energy out of the drivetrain and vehicle to pump that energy into the HV battery. It is a GENERATOR that acts like an INTERNAL BRAKE and the gauge needle moves to the LEFT into "CHARGE" in response. What you're saying is that for some reason, your generator motor is going into "regenerative braking mode" in a very harsh way, without you touching the brakes and quasi-randomly, but mostly after the car hasn't been driven in a few days, which means that the HV battery has sat for a couple of days and may not have a steady state of charge yet (or maybe it is developing issues of its own, with some cells "on the brink.")

The smaller motor/generator can also be powered directly by the gas engine even if the vehicle is accelerating, to tend the battery!

Quite often, in fact, you have a stable powertrain situation (and I know this from watching the "marching ants" on my SYNC/NAV Information screen) like:

1) Gas engine is supplying torque to turn the wheels and propel the car down the road
2) Traction motor (big electric motor) is supplying torque ALSO to help propel the car down the road which means:
a) It is REMOVING energy FROM the HV battery.
3) SOME of the Gas engine's torque is being "diverted" to the Generator to maintain the battery SOC which means:
a) It is SUPPLYING energy TO the HV battery.
4) You are listening to AC/DC's "Live Wire" on the stereo with
5) The electric air conditioning compressor ON to keep you cool in the summer (my '10 has electric A/C.)

Meanwhile the car is in cruise at a constant speed of 70 MPH on flat ground. It is neither perceptibly accelerating nor decelerating, but there's a whole lot of electromechanical conversion and computing action going on behind the scenes. High tech stuff. The computer is doing its best at all times to maximize the efficiency of the drivetrain while providing the power the driver is asking for to move the vehicle - by combining the various parts and balancing them. It evaluates and updates its strategy many times per second.

If you have an HV battery that is telling the computer: "Help! I'm waaaaay below where I should be! Refill me!" In a transient fashion, that could be triggering the computer to activate the generator motor and attempt to supply some charge. Then all of a sudden it straightens out and all is well again...until the next time.

I think the only good way to diagnose this better would be to really fire up FORScan and monitor some appropriate PIDs in real time as you drive, and in particular try to catch it when it happens. It definitely sounds weird, because to you the driver it will feel like you've hit the brakes or "stabbed" at the brakes - but it's taking place from inside the transaxle with no input from you! Maybe SKeith has some experience tracking down something like this?

The transition into and out of "charge" on that gauge should be SMOOTH. It's definitely alarming to hear your description, because it sounds to me like the generator is coming on STRONG, acting like a BRAKE, and then the computer decides: "Whoops! Nope. Nothing to see here!" and the system returns to normal.

 

Thanks AlexK for the thoughts. In my case, I watched the charge/assist gauge more closely when it happened again. It first goes high into the assist range before bouncing back to either zero or deep into charge. It seesaws like this for a bit while the vehicle bucks before going back to normal. My current theory is that the engine is hesitating somehow and the motor/generator initially assists to make up for the missing torque, but then the engine is back and suddenly there is too much torque and the motor/generator (or traction motor?) tries to absorb it through charging.

I don’t think the HV battery is the issue, I have to drive 15-20 minutes on city streets before even getting to the freeway. Sometimes I get into EV mode before hitting the freeway. It’s that next 20-60 minutes of high-speed driving (but still sort-of cold) when the bucking is likely.

I have an AWD, I had the PTU fluid checked a while back and it was good. Transmission fluid replaced about a year ago. I visually inspected the throttle body and airflow sensor; both looked clean. I’m thinking the next thing might be replacing the spark plugs; I don’t know if/when that was last done.

Good idea about monitoring on Forscan. I have been wanting to do that during one of these events. Problem is it’s fairly infrequent, although I’m starting to recognize a pattern and can probably catch one soon. What PIDs should I check besides BSOC? I was thinking maybe fuel rail pressure to rule out any fuel delivery issues. Traction Amps from the battery might be useful although I think the charge/assist gauge just mirrors that. Anything else?

 

Check out fuel trim. Instant and long term. If its adding then you have a fuel issue. Timing advance might be helpful to see what the ignition system is doing. Leave it logging so you can make nice graphs and see what happened vs RPM and engine load.

 

Thanks for your help... Yes... mine is a 4wheel drive model... 2007...

 

Update on this: I had the spark plugs changed out in late April along with an oil change and engine air filter replacement, and the jerking problem hasn’t happened at all since then. Although it’s also getting warmer out so possible this is a coincidence, but that’s my observation as it stands currently. I’ll post another update if this changes.