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Discussion Starter · #1 ·
Hi there. Just bought a 2014 ampera 80,000miles and full history. It has developed an intermittent loss of drive and only seems to happen at very slow speeds and on slight left hand turns. No warning lights come on and dash stays illuminated as usual. Anyone ever had any issues like this? the car drives excellent besides this.
 

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Very strange! This car just loves to illuminate the engine warning light (EML) at the slightest provocation! When you say "loss of drive", what happens, does it just slow gently as if you'd feathered the throttle? And if so, does pressing the throttle more recover back to normal? Does it behave the same in Sport mode? that needs less pedal press to get the same speed, maybe there's a dodgy resistance in the floor pedal that only shows up at a particular pedal height & when your foot is being pushed to teh right by conering acceleration? (grabbing at straws here tbh...)
Or is it a bit jerky like a petrol misfire might be?

Might be worth taking a careful look at the tyres, esp the front? I'm wondering if the left is worn a lot more/less than the right, maybe there's a rather larger speed differential for the turning angle than the car expects, so maybe it thinks the wheel is skiddng & the traction control/ABS is doing something funny? There's a traction-control switch above your hed in the centre, might be worth playing with that & see if it makes a difference.
 
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Discussion Starter · #3 ·
Hi Andy, it feels like a faulty pedal sensor. The just looses all throttle response and then just takes of again in a few seconds. Happened 3 days in a row now and always in normal driving mode. Just curious if there is a common problem. I'm a trained technician myself and know how hard these intermittent faults can be to find. Thanks.
 

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Do you have the Volt Service Manual? Appx 75 Mbyte PDF? This has diagrams of where the bits are located, how to swap them out etc. I have no idea if it's resistive (could wear out thx to friction), inductive, capacitative, Hall-effect, or what. But it might be worth finding the connectors and giving them a dose of switch-cleaner fluid & re-seating them. and dosing the pedal as well, if you think it's safe to! Msg me if you want the pdf, I can put it up on dropbox for you.
 

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This sounds a little bit like what I had with my car a few years back.

I would be travelling on cruise control at about 60 and a gentle left hander bend would knock it off. Entirely reproducible on a particular bend.

Have you recently had tyres replaced, or are back much newer than front, or vice versa?

I think it was @donald who suggested this, it being due to slightly different circumference of the new tyres v. the old, and triggering traction control albeit momentarily and virtually imperceptibly.

If so get them swapped over. This fixed it for me (to my surprise, though if @donald says it there's a good chance he's not wrong!!). From my post here, the newer ones being on the front fixed it.

Hope that helps!

EDIT: This post also discusses this issue
 

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It is not a 'suggestion' from me, I would grade the comment much higher than that.

I am making statement of absolute technical issue/requirement that needs to be ensured one meets.

I did extensive laborious tests to prove this out.

The front tyres need to have a larger rolling circumference than the rears.

Now, whether there is a secondary issue is a different matter, but one must fit tyres of equal or greater rolling radius to the front, particularly to the right side.

If you have a range of tyre rolling radius (due to wear*), fit the largest to the right front, next to right rear, then left front and smallest to left rear.

*If they are different because they are different brands/types, junk them and buy matching tyres (at least across the same axle).

Tyre pressures equal all around, I recommend 40psi for all tyres.
 

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Also note that if you have more tread on the front tyres than the rears you must ensure your rear tyres are in VERY good condition. It is best practice in ice cars to put the new tyres on the rear and move the old tyres to the front. NEVER fit new tyres to the front of a car and have old tyres at the back - that makes the car wildly unstable in very wet conditions, or at the limit of grip. Sometimes it cannot be avoided - some cars have different sized tyres front to rear for example, but then you often have to replace the rears well before they need it.
 

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Several you tube videos about it here....



All major tyre manufacturers say the same. Only KwikFit say different, they clearly haven’t a clue what they are talking about, given the quality of staff I’ve seen and experienced in there!
 

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Discussion Starter · #9 ·
It happened when I bought the car and had 4 very good matching tyres and it also happened again with 4 new tyres fitted. I would be quite confident that it's not a tyre issue on my car. The best way to describe the fault is as if the throttle pedal has a bad track in the potentiometer,loss of drive then just comes back again. Very dangerous when pulling away from a junction.
 

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Discussion Starter · #10 ·
Do you have the Volt Service Manual? Appx 75 Mbyte PDF? This has diagrams of where the bits are located, how to swap them out etc. I have no idea if it's resistive (could wear out thx to friction), inductive, capacitative, Hall-effect, or what. But it might be worth finding the connectors and giving them a dose of switch-cleaner fluid & re-seating them. and dosing the pedal as well, if you think it's safe to! Msg me if you want the pdf, I can put it up on dropbox for you.
Hi Andy, that volt service manual would be great to have. If you could send me a copy would be much appreciated.
07921760250 or [email protected]
 

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I can find no other record of a fault with this description here or on the Volt forum.

I'd appreciate a little more detail on the the failure mode, so here are some questions:
  1. Does it happen equally on light, medium or full throttle?
  2. Are the effects noted in (1) the same in D and L?
  3. Does it happen in Reverse?
  4. Does it happen with the Traction control turned off?
  5. Does it ever happen in a straight line?
  6. Is it only left hand turns?
  7. Is it repeatable?
 

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Discussion Starter · #12 ·
1- it happens on different mid light and full throttle.
2-only seems to happen in D mode as this is my preferred mode to use.
3-never happened in reverse (yet)
4- never tried traction control off, but never have any warning lights come on.
5-happpens in a straight line occasionally but mainly on slight left hand turn. And at a variety of speeds.
6- can't get it to replicate it just happens randomly.
I have since noticed that the D light goes out on the shift lever and the dash display so possibly a shift lever fault??
 

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Thanks for quick reply. From what you say I am inclined to rule out the throttle pedal because it happens a different levels of power demand. My question on L & D was aimed in that direction also because the throttle will be at a different position for any given power demand.

You last comment on the shift position indicator is interesting. That could be a loose connection somewhere, but might simply be the display reacting to the computer taking control. Need access to a skid pan really to fully understand what the behaviour of the display should be.

For my money, TC taking control has to remain favourite for now. The reason is not completely clear though - it could be a wheel speed sensor fault if not the tyres - so disabling TC for a while would be a useful additional test. A faulty yaw sensor is another outside possibility, again turning off TC would eliminate that. Some systems do not completely turn off TC even when the switch is off, so it may not be conclusive, but it will be interesting to see if there is any effect.
 

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Discussion Starter · #14 ·
There are also 4 new tyre fitted so I can rule that out also, and it was doing it before they where changed. Had it on a scan tool and no faults at all in any module. I've been a mechanic for the last 24 years and was a vauxhall tech for 8 of those and I know how difficult an intermittent fault can be to find. I'll try it TC off and see what happens. Thanks.
 

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1- it happens on different mid light and full throttle.
2-only seems to happen in D mode as this is my preferred mode to use.
3-never happened in reverse (yet)
4- never tried traction control off, but never have any warning lights come on.
5-happpens in a straight line occasionally but mainly on slight left hand turn. And at a variety of speeds.
6- can't get it to replicate it just happens randomly.
I have since noticed that the D light goes out on the shift lever and the dash display so possibly a shift lever fault??
Sounds very much like the shifter switch based on the above. Having a look at some shifters on eBay it looks as though the shifter moves a cable - so the actual switch is probably not in the shifter itself. Could be the cable is slightly stretched so in 'D' position it's not quite aligned properly - might be possible to adjust the cable tension?
 
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