Occasional 'surge/clunk' when switching from ICE to HVB

[snwbrdngtr]

So I've been driving my '13 for a week now, mostly short trips and errands (where else am I gonna go right now?) and I'm in love with the car! I think I have my driving pretty well adjusted now (thanks to all the wonderful help from this forum!). A few times when the car switches from ICE to HVB or HVB to ICE I feel a small surge or clunk from the engine bay. Reading about the high incidence of tranny failures I immediately got a little nervous... Is this something that the car is known for or should I be concerned? I'll also mention that the temp has been in the high 80's/low 90's this week so may be temp related?

Thanks for any thoughts on the matter!

[plus 3 golfer]

There should be no clunk when switching from EV mode to ICE and back to EV.  But, I doubt it is the transmission.  It's more likely engine / transmission mounts or something in the front end suspension / cv joints / maybe steering.  What are the inputs to the car when it happens? accelerating, decelerating, braking, uphill, downhill, coasting, cruising, low speed, high speed and so forth?  How many miles on car?  It sounds perhaps that when there is a change in torque requirements (whether in EV or ICE), you sometimes get a clunk (like one does when a CV joint has failed).  Have you had the car serviced recently?  If so what did they do?

[SnowStorm]

By any chance, are you driving in 'L' instead of 'D' or using the hill assist function (button on left side of shifter)?  I remember some nasty clunks when using these modes - especially 'L'.  I never use 'L' anymore - better to just use the brakes!

[C-MaxA2]

I have some shaking sometimes when I stop - as if ICE continues to run a bit when it tries to go off at a light.  Starts up again fine when the stop light changes and ICE engages.  Doesn't throw a code so I hesitate to take it to the dealer but it's still under warranty til Oct. so I'd like to have it on the record before the warranty runs out.  Esp. when the car has sat for a while (overnight).  

[kyledamron1]

Have you changed your spark plugs?

[C-MaxA2]

My C-Max is a 2017 (Hybrid) with 17,700 miles... should I have changed the plugs already?  Seems very early.  It's been to the dealer twice since we bought it in March this year and they've never suggested replacing the plugs and they're 'dealers' who never miss an opportunity to sell something.

 

We also have a 2016 with 12,500 and it's never done this. 

[snwbrdngtr]

7 hours ago, C-MaxA2 said:

I have some shaking sometimes when I stop - as if ICE continues to run a bit when it tries to go off at a light.  Starts up again fine when the stop light changes and ICE engages.  Doesn't throw a code so I hesitate to take it to the dealer but it's still under warranty til Oct. so I'd like to have it on the record before the warranty runs out.  Esp. when the car has sat for a while (overnight).  

This describes the feeling pretty well... I just bought the car so I haven't done plugs yet, been working too much to really dig into those areas. I did read another (older post) about issues with the motor mounts, it could certainly be something related to that!

Thanks for easing my mind about the tranny!

[plus 3 golfer]

On 6/3/2020 at 1:02 PM, C-MaxA2 said:

I have some shaking sometimes when I stop - as if ICE continues to run a bit when it tries to go off at a light.  Starts up again fine when the stop light changes and ICE engages.  Doesn't throw a code so I hesitate to take it to the dealer but it's still under warranty til Oct. so I'd like to have it on the record before the warranty runs out.  Esp. when the car has sat for a while (overnight).  

1) If ECT is above a threshold (around 130 F maybe lower down to 100F), ICE shuts down when you take your foot off accelerator (no spark or fuel to engine).  With foot off accelerator, the traction motor provides regeneration to simulate engine braking of a normal car.  Once speed is under around 5 mph, regeneration stops and friction braking takes over to stop car.  Any clunking / shaking at this time is not ICE.  The clunking / shaking is more likely associated with stuff like loose caliper bolt, worn suspension and the like (something moving / rubbing) but maybe an ABS sensor (but there are checks to detect whether sensors are working and within limits). 

 

2)  I don't know the algorithm used but if ECT is below a threshold, ICE will continue to run until virtually stopped or at least until rpm is under say around 900 -1200 rpm (ICE spinning and can supply torque to generator while coming to stop).  So, it's likely ICE could cause a slight shake as it shuts down at a complete stop and it may be dependent on torque supplied to generator (goal is to run ICE as much as practicable to get ICE up to temperature for closed loop operation).  It's also likely that if HVB needs charged (below a minimum SOC threshold), ICE torque could change as car is slowing down especially under 5 mph when regeneration stops to continue charging HVB.  This might result in a greater amount of "shaking'" when ICE shuts down at stop.  I have noticed what I believed to be normal shuttering of ICE when I lived in eastern TN for a few years when ECT was well threshold and ambient temperatures were cooler (don't recall what temps maybe under 40F). I attributed this to all parts, mounts and bushings were stiff due to cold temps.  In Phoenix where lowest temps in garage might be 50-55F, I don't recall ever noticing this shuddering.

 

3)  Put the Engage display up.  Watch the display to see when ICE is supplying power and when EV is supplying power.  You should see that once ECT is up to temperature, ICE shuts down, if on, when you back off the accelerator.  If you are not up to temp and ICE is on when you first start car, you might see at the first stop, that ICE will stay on when you release accelerator, then when you reach around 5 mph, ICE power might increase and not go to zero until stopped.  So, does the shaking happen no matter what the ECT and ambient temperature is?  I just came back from a trip to the gym.  Both going and coming back, ambient was about 90-95 F.  ECT was under 130 F.  Both times ICE ran until the first stop just maybe 300 feet. After that ECT was well above 130F, ICE never ran coming to a stop.  Also, your plugs should be good for over 100k ICE miles.  If plugs were an issue (or other ignition components), you would likely have misfires, DTCs, and maybe CEL.

 

  

Edited June 4, 2020 by Plus 3 Golfer

[plus 3 golfer]

The following are reasons ICE may be on while you are coming to a stop and then perhaps suddenly shut down because the reason causing ICE to be on was no longer present.   Could this cause a shudder (shaking) as ICE kicks off and back on on startup?  Also, when applying brake ICE is turned off but for the ICE on conditions below.  

  

• The engine will be off unless it needs to be on for reasons other than tractive power (Max A/C, vacuum,
catalyst temp, heat, purge, low SOC)

 

I see ICE on in AZ upon startup due to Max A/C virtually all the time when car is left out in sun and temps over 100F.  It might be several minutes before Max A/C is reduced.  What happens is that ICE runs generator to both charge HVB if needed and to supply power to the A/C compressor directly.  When stopped, ICE turns off and power comes from the HVB to run compressor.   But, I've never experienced any shudder during this ICE on (moving), ICE off (stopped), ICE on moving.  I'm struggling to find any rationale for the shaking when coming to a stop and starting up again other than mechanical.

 

 

 

 

Edited June 4, 2020 by Plus 3 Golfer

[snwbrdngtr]

Well, now I feel like 'that guy'... I think I did have the A/C running when this happened but I honestly don't remember! It has been a little cooler here the last few days so I've been driving with the windows down rather than running the A/C and I haven't noticed it. I'll pay closer attention going forward.

Thanks for all the replies everyone, I've only been here a week and I've already learned a lot!

[plus 3 golfer]

8 hours ago, snwbrdngtr said:

Well, now I feel like 'that guy'... I think I did have the A/C running when this happened but I honestly don't remember! It has been a little cooler here the last few days so I've been driving with the windows down rather than running the A/C and I haven't noticed it. I'll pay closer attention going forward.

Thanks for all the replies everyone, I've only been here a week and I've already learned a lot!

In the left hand display, go to MY VIEW and set it up to monitor accessory power.  I don’t know what  the algorithm considers “max A/C load”.  But I have seen up to around 5 kW of climate load and ICE is on. I never monitored to determine what climate load turns ICE off.  Once the cabin reaches set point temp the climate load will generally be less than 500 Watts.  So, now you should be able to determine if climate load is causing ICE on and whether you get the clunk.  

Edited June 5, 2020 by Plus 3 Golfer

[C-MaxA2]

I've set up an appointment to have the Ford dealer look at the issue.  I may end up leaving it overnight so they can start it up cold the next day and see what happens.  I almost always have the AV (and Heat) off when I start the car.  It's curious because our 2016 has never done this.  Same distance, same cold start, same stoplight so I feel it's not right.  It's not a showstopper but not a good sign and I don't want to let it get to the stage where it's the 'new norm'.