Handling during throttle lift-off

Hi all New hear so be gentle. Im trying to buy a C4s convertible and took one for a test drive today. Nice tight gearbox - barely any movement of the gear stick (yeah, OK shifter) once in gear. This car has 65k. One I took out with 48k had about 25.4mm lateral movement once in gear - hmmm, Anyhoo, this isn't actually my query but comments welcome. When accelerating hard during test drive and taking foot off the throttle there was an awkward shift in the balance of the car - seemed like pulling (or pushing) in one direction - I think towards nearside of road, but this could be my imagination. The man point was that it felt unbalanced and was not a neutral response to throttling off from hard acceleration. Any thoughts why this might be? Many thanks in advance.

Tires, alignment, loose suspension components, lot's of possibilities.

We you going straight when you lifted?

Edited. Mods please delete. My idea didn�t make sense for car going in a straight line.

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Yep. Didnt feel anything odd when accelerating, even if not foot down. No wheel wobble and no pulling to near side from affect of road camber - until lifting off after hard acceleration. BTW it was not huge, but certainly noticeable. Also, didn�t notice this on different c4s test drives. Cheers G

Bad motor mounts? There's 600 lbs sitting back behind the wheels - when the mounts are bad, you get that weight shift feeling when lifting off the gas. It feels even stranger in turns...

First thing that comes to mind is checking tire pressure. My car felt awful when I first pulled it out of the garage this spring, set the pressures that afternoon at the shop and it made a world of difference. If this car has been sitting for a while I would certainly start there.

^^^^^ this ^^^^^ My 2004 C4S behaved this way when I had one nearly flat rear tire. It was like the car would �yaw� left or right under hard acceleration, or when lifting off the throttle. That was 10yrs ago. Car has 92k mikes now and recently I am also feeling just a bit of this. I know my front strut bearings are bad (I can hear them) and maybe front strut mounts too. So I�m hoping to see a change when I replace those parts.

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Interesting suggestion. Is that a complicated/expensive fix? Are these mounts susceptible against age or mileage or even the way the car is stored? G

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To be fair, I presumed the dealer had tyre pressures sorted... so could be a factor. As for strut mounts - no knocking heard and nothing noticed when turning lock to lock in a car park, nor over typically bumpy UK road surface; but, certainly something to consider. Thanks for reply G

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No, very easy and inexpensive to address, especially if you DIY. Primarily they wear out with age and start sagging a bit. That could be what's going on here but I'm skeptical...seems more suspension related to me.

Many thanks G

Look at the tail pipes, they should be tucked under the bumper tightly, if there is a large gap that doesn't look right, it's the motor mounts. It causes the engine and hence the tail pipes to sag. When you replace them, it's amazing the difference it makes. Takes about an hour or so to do it yourself.

$1 says you need to check your suspension. Worn b ushings, etc. can allow the drive wheel angle to change under acceleration; unloading the drivetrain changes all of that geometry when there is slop. Don't ignore any issue where the car makes funny noises and feels wrong. I was cruising along on a surface street at approx. 35MPH when I heard a POP from the rear and the handling immediately felt wrong. Three of five wheel aftermarket studs failed catastrophically at the same time (that was the pop), and the slop was from the flex introduced by the wheel only being held on the hub by the 2 remaining (adjoining) studs. I don't run studs any more.

I had an instance once on a customers car where one of the rear toe control arms was not sufficiently torqued. It would cause a shift in rear toe on one side during hard acceleration or deceleration. An alignment with proper torque cured it.

My car came with mis-matched front and rear tires. The car felt like it wanted to kill me every time I got aggressive driving curvy roads. The front wanted to do one thing and the rear another. I swapped a new set of front tires that matched the rear, and my car finally felt like a 911 should. So, how are your tires?