Uneven start

[mark h]

When i start from cold the tick over is uneven , and a plip on the loud pedal only gives an uneven rev. Also the rev counter does not work. However , after a couple of minutes warming and a good prod on the loud pedal , the rev counter jumps to life and the uneven running disappears. Any ideas?.
I seem to remember that earlier threads advised the disconnection of the ecu for 10 mins to reset any stored faults/errors , would his help?

>>> Edited by mark h on Sunday 21st September 08:48

[suffolkfox]

Firstly the two problems may not be connected. The rev counter may have a dodgy contact that needs to exceed a certain voltage before it comes live. I've got one on my speedo at the moment which jumps to 35mph from zero when I first reach this speed then settles down, so a fiddle is needed. The idling may need further investigation, but could simply need the ECU resetting as you say. However, unplugging the ecu will not reset the maps & fault codes as the unit has a memory. You will need to plug the unit into the software to do all these things. You will have to find someone who has it and knows how to use it or go to a dealer.

[gazzab]

Is it really an uneven rev or is it just the rev counter reading?
The rev counter can be a problem when the 'big fuse' has gone / going or the battery is starting to go.

[markys]

Where is the big fuse ? My rev counter has started to become a bit stuck first thing in the morning, battery is ok.

[gazzab]

The big fuse is for the alternator and is behind the engine. You need to remove the plastic inner bonnet thing and then take a long reach socket (cover it in tape to avoid shorting) to change it. It is worth changing it once a year as it cracks and it could leave you stranded (and generally the AA dont want to help fix or bode it to get you home).

[markys]

Where do you get the 'big fuse' from, how much should i expect to pay.

[gazzab]

From a dealer. I got a couple for free from Fernies and keep them in the car. I cant believe that they are more than a few pence each.
They are 100amp.
You can hard wire it if you wanna just get home.

[markys]

Does anyone have any pic's of the fuse and of the location to aid me in replacing it.

[gazzab]

It is just a flat thin piece of metal - about 2 inches long and 1/2 inch wide. With a 'D' at the top and bottom to allow it to be screwed in place.
On a 4.5 cerbera it is right behind the purple trumpets and about 12 inches down.

[markys]

Does anyone know where it is on a 4.2 ?

[RichardP]

In roughly the same place, behind the engine on top on the bell housing.

[markys]

Can the fuse be purchased anywhere other than TVR, its a bout a 75 mile round trip but Halfords at the end of the road.

[gazzab]

good excuse to go for a drive!?
Not sure if it is the same as a standard fuse.
If you have a good relationship with a dealer then maybe they might drop one in the post or tell you where else you can get one?

[markys]

So far havent needed to goto a dealer.

[mark h]

Sorry for the delay in replying , I have changed the big fuse previously , so that is not the problem. Next step is to get the ecu faults erased. Just a note regarding the big fuse , Halfords had never seen this type of fuse before, however TVR at redhill had and its replacement cost a whole 72 pence.

[markys]

We have a Lucas Electrical store near by worth asking, does anyone know what other car its off ?

[suffolkfox]

mark h your profile has no email, might be worth adding one.

[Mark H]

Email sorted!!