Cerbera 4.2 V8 fuelling

[macgtech]

Someone I know owns a Cerbera and recently it has been running slightly 'rough' at trailing throttle. Driving the car at constant speed, the car won't run smoothly, and jerks slightly, (not aggressively) like it is choked up. It is also using excessive amounts of fuel and smells rich when running - all of which points to over fuelling.

Now, I suspect it is down to the fuel regulator. On the photo below, you can (just) see the fuel regulator between and just under the fuel rails, but it has no vacuum hose connected to it. Should it have a hose attached? If it should, it would be running the fuel pressure 1 bar too high, and thus would over fuel, but I do not know whether or not it should have one connected, and if so, where the other end goes.



Link here for a bigger version: http://twitpic.com/8atx1u

There is no obvious hose that is not connected, but I didn't look very hard as there is a lot of wiring/leads hoses etc around. Any information would be appreciated.

Thanks

[gruffalo]

Most common cause of this sort of problem is either throttle pots or a Lambda has gone south for the winter.

[Cooky]

Firstly get rid of the cats, that will render the Lambdas useless, then set it up again. Most 4.2 cats unless recently changed will be spent by now.

[Tanguero]

No, the fuel regulator on a 4.2 does not have a vacuum hose attached. The vacuum nipple should be unconnected.

Throttle pots or lambda sensors or their wiring would be prime suspects as mentioned above.

[macgtech]

Thanks for the information - what do you refer to by throttle pots? For some reason I thought the Cerb had a throttle cable not DBW?

[macgtech]

Cooky said:

Firstly get rid of the cats, that will render the Lambdas useless, then set it up again. Most 4.2 cats unless recently changed will be spent by now.

Hi Cooky, the cat's were changed reasonably recently IIRC.

[tejr]

macgtech said:

Thanks for the information - what do you refer to by throttle pots? For some reason I thought the Cerb had a throttle cable not DBW?

Cable is connected to the butterflys which in turn are connected to the throttle pots which feed the signal to the ECU

[macgtech]

tejr said:

Cable is connected to the butterflys which in turn are connected to the throttle pots which feed the signal to the ECU

Ah - Throttle position sensor!

[Tanguero]

If it is only rough running then it probably just needs the throttles set up properly using the diagnostic software and an airflow meter. There are step by step instructions in the Engine section of the workshop manual. Both can be downloaded from here http://www.tvr-cerbera.co.uk/

[Hawkeye1922]

Another fiver on a dead lambda.

plug in with a laptop and check the adaptives - if there's a large area of the map up at 37.5% it's pretty conclusive