V8V Throttle body

[Gmw76]

I have read various posts on this but some explanation for a relative newbie please. Last week my car apparently lost all power for just a split second on acceleration. It was extremely quick and came back to full power straight away. I don't thinks it was a misfire on one cylinder as the result was more power loss even though overwith in a blink. Does this sound like the oily throttle body and butterfly valve?

I know this may sound obvious but can I assume the throttle on the car is 'remote' from the pedal. I.e. no cable? As if there was a cable and spring I would have thought cable pull would overcome any sticky substance.

If remote. What is the mechanism which cannot just pull past and oily residue. Is it some form of servo with little power or a more finely balanced affair.

Sorry for so many questions but it was a bit heart stopping so looking for help on what it was and if you guys think it may be throttle body, then secondly looking to understand the failure mode.

Thanks
Mark

[Impasse]

You're not the only one to have suffered this and blame seems to directed towards the throttle pedal assembly rather than the throttle body.

[JohnG1]

Details of car - which model year?

Had you recently filled the petrol tank?

Had you been taking a series of corners or been round roundabouts before?

What was the weather like?

I had a similar problem with my V8, so these questions are all directly relevant...

[BravoV8V]

I used to get this problem very occasionally with my '07 V8V coupe.

However, since getting the exhaust manifolds and cats changed at BR, the problem hasn't returned. This might be a coincidence or it might point to the issue being 'downstream' (rather than 'upstream') of the engine.

Then again, BR might well have cleaned the throttle bodies when they did the work. I don't know about that detail though, I'm afraid.

[mjk1]

Also used to get this momentary loss of power on my 06 V8V. Can't see how it can be a sticking throttle valve though. A momentary loss of power would require the valve to flick shut and then open again. Hence the opposite to what a sticking valve would tend to do. Stratstones Derby updated the ecu software which appears to have cured mine.

[Gmw76]

Thanks so far guys.
V8V 2008 coupe. Tank was full, but filled the day before. I had just taken left hand 90 deg bend on a junction so 15-20mph 2nd gear and it was on the acceleration up from that. Recently had service inc 2 new o2 sensors. Any clues there?
Weather was dry and quite warm but 8am in the morning so say 19 deg
Mark

Edited by Gmw76 on Wednesday 20th August 18:38

[W1111AM]

There's a fuel pick up pump issue known that causes this intermittent issue on the older V8V, it's in the tank. AM changed it for later models. I believe it will only happen occasionally. The problem is you cannot show a mechanic because you can't simulate the fault. If it becomes regular then take action.
John was also right about tank level and bends, there is also a know issue with fuel slop in the tanks.

[JohnG1]

Gmw76 said:

Thanks so far guys.
V8V 2008 coupe. Tank was full, but filled the day before. I had just taken left hand 90 deg bend on a junction so 15-20mph 2nd gear and it was on the acceleration up from that. Recently had service inc 2 new o2 sensors. Any clues there?
Weather was dry and quite warm but 8am in the morning so say 19 deg
Mark

Edited by Gmw76 on Wednesday 20th August 18:38

Hmmm. The issue I encountered was caused by the fuel tank air purge valve dumping fuel into the inlet manifold. This causes the ECU to stop the spark and therefore engine power is reduced to zero. Once the excess fuel is out of the engine then the spark starts again and the engine will revert to normal.

This failure of design is generally discovered with a full petrol tank and a left turn.

AML after-sales engineering know all about this issue - the dealer network not so much. I had a guy from Gaydon come out for a drive with me with a laptop plugged into the OBD2 ports. That trapped the issue.

To fix this the petrol tank had to be removed. Which means disconnecting to torque tube from the engine block, removing the rear suspension sub-frame and transaxle and then removing and replacing the tank. I didn't pay, but I was told it's £3000-£4000 or so (this was in 2009).

You can try a main dealer but it may be very hard to get them to assist (I only managed it due to bloodyminded stubborness and the fact that the car I bought had been owned by the father-in-law of the salesman. Hence they knew the track record.

Due to the age of this car, my suggestion would be to get a decent independent like Bamford Rose to look at the car. If they agree with my analysis then pay a main dealer to do a 140 point check and take out a warranty. Then wait a little while and claim on the warranty.

[Gmw76]

Wow

Thanks for that. Yep full tank just having done a left turn. My car is still under dealer warranty. I guess I could tolerate if I new it didn't happen on less than full tank. Are we aware of many people having this issue diagnosed and addressed?

Mark

[JohnG1]

There are a handful of folks on here (I've spoken with a few of them) and I've been told that there are more people who hit this problem.

Since it's under warranty, happy days.

It's not that it's only a full tank. It can be less than full but on a very hot day where the fuel vapours in the tank are dumped into the inlet manifold. I had both types of failure...

[huggy1]

I had this a lot (3 years ago) but not so much now, once every 3 months or so, it was happening and within a day or two the car would suddenly go into limp mode. I had under warranty at Works Service-

1 Throttle body cleaned
2 Throttle body changed
3 ECU re mapped
4 ECU changed
5 Tecchies from Gaydon playing with it.
6 Everyone just gave up

I was told by the AA warranty technician, that apparently it's a sensor in the boot area, don't know if this relates to comments about the fuel tank.

[SL500UK]

This has happened to my V8V (07 model) probably half a dozen times in the past 4 years. Very much doubt if it has anything to with the weather/road conditions or when the fuel tank was last filled up etc, it just tends to happen when I depress the accelerator heavily. A bit of a shock when you want a lot of power but get the complete opposite for half a second or so. I've not looked into it any further because a) it doesn't happen very often and b) I can't replicate the problem no matter how much I try.

[huggy1]

So it's a 'They all do that sir' fix.