V8 vantage throttle sick but not throttle body

[michael-o1z5e]

Would appreciate any input. The vantage has developed a problem, I've cleaned the throttle body but with no avail. The problem persists, the higher the revs the more likely it is to start self revving in and out of gear.

Any advice or diagnosis ? I'm south east kent so nearest garage is 1 1/2 drive

Edited by michael-o1z5e on Wednesday 20th May 14:29

[simonpa]

Does the idle stay steady?
I think it also helps with keeping revs high between gears (granny function) to help gear changes.

You can try cleaning the contacts on the plug to the butterfly stepper motor, plus the idle control valve.

[michael-o1z5e]

Yes idle is steady, sorry I should have made more sense, after driving and revs reach over 3000 the car starts lunging forward, so I'll take it out of gear and coast, the revs then fluctuate before maybe revving up to around 4500-6000.

[simonpa]

I doubt the IACV could let it go that high.

I'd try cleaning the throttle electrics - if that doesn't help, ECU reset may do it.

[krisdelta]

Could be an ABS / speed sensor on one of the hubs, an AM diagnostic machine will pick it up. I had this - the car surging with no warning. Was a hub swap (part @£300 iirc). This is how I ended up writing the throttle body cleaning guide as this is where I started too

[simonpa]

Interesting.

I would have thought that would have thrown a code, as all sensors should be showing similar outputs.
The system is quick to alert if it thinks a wheel is spinning or locks up..

[krisdelta]

It throws a code - but nothing that ends up on the display in the car or a plug-in code reader. It needs the AM diagnostic software I believe.

[BamfordMike]

krisdelta said:

It throws a code - but nothing that ends up on the display in the car or a plug-in code reader. It needs the AM diagnostic software I believe.

everything you say about wheel speed sensor is correct, the symptom the OP states could well be this issue. If not then sounds symptom to a throttle pedal fault. The fully closed flag doesn't trigger when no demand is requested. Strange enough too, this problem also tends not to set a MIL even though a positive torque mode is in progress which has not been requested by driver. Either case, this problem needs the diagnostic kit

[michael-o1z5e]

Since last posting I've not had the time to send in to AM, I have however taken it around the block to see if it was drivable to reach Sevenoaks, and issues as follows.

It's not over self revving at all now, it drives like it use to all but. I've had a few lights come up as follows

Pictures
Traction control
ABS
Hand brake
Red triangle warning

Display
Traction control temporary off
ABS / DSC service required
Emergency brake assist failure

Has this happened to you / especially krisdelta ?

Will it be ok to drive hour or so to drop in and what's your recommendations ?

[Manwhoneverwas]

I had ALL the warning lights on my dash you describe (but NOT the over revving)
The AM dealer replaced the speed sensor on the front offside hub and it cured the problem for a day then the lights came on again.
It turned out to be water inside the two wire harness to the speed sensor, they replaced the wiring and that cured the problem.

The car was drivable, but it is very unnerving driving with all the warning lights and in the case of my Sportshift gearbox the fault prohibited down shifts which makes for a very interesting drive home in peak hour traffic.
I got the AA to flatbed the car to the dealer

There is a kit for sale here which replaces the sensor wiring

http://astonmartinbits.com/models/5-V8-Vantage/par...

Is you car a manual or Sportshift?

Edited by Manwhoneverwas on Wednesday 27th May 15:41

[michael-o1z5e]

Thanks, yes it's a manual. The lights arnt on all the time they've only come on twice but when on ot doesn't over rev.

I've changed the abs/ speed sensors, I assumed it wouldn't need resetting each time as I only brought one and frog leaped them to the next each te I test drove it, still no avail.

[michael-o1z5e]

I'm guessing the speed sensors pick up spaced magnets in the hub which give the reading, do these magnets deteriorate or become un-aligned ? * above especially did aston Martin tell you what happened to your hub when they replaced it ?

I did have a little bump on a curb maybe 7-8 months ago and had to change the alloy, do you think that may have something to do with the problem.

Regards

[Manwhoneverwas]

Sorry, but my technical knowledge is limited to my own personal experience (offside front speed sensor wiring and connector replaced only)
I have also heard of a rusty hub also being a potential issue, but as these parts are circa £300/pair it would be an expensive trial & possible non solution to the issue.

I would doubt the change in alloy wheel would cause an issue, in my case I have replaced all my alloys with a newer AM style alloys with no issues.

You could try cleaning the hubs with a wire brush to remove surface corrosion.

[Fronkle]

Mike,

I am having the exact same symptoms re the lights and then the runaway over rev.

Did you ever manage to identify the problem?

[Fronkle]

Vantage V8 back from SevenOaks.
Diagnosis: wheel bearing starting to fail generates faulty signals to wheel sensor.
Remedy: new wheel bearing; £800 all in.

[TopT]

Hi,
I have a similar but not quite the same problem with an AM Vantage V8 2015 model. It loses throttle control, slips into idle, but resets once i switch the engine on and off.
No dashboard error codes and 6 trips to AM garage where the can’t find anything wrong!
Any ideas? It’s driving me bonkers and i think it’s unsafe, but the garage seem to be fed up looking at it.

[Riddochg]

Try calling James at David Appleby. He’s highly likely to have some ideas. Top bloke!

[TopT]

Nice one - thank you!