Help: loss of power on 4.5 cerb

[glennmoore]

I was driving down the motorway when the car developed a dead spot at around 5000 revs, it could hold the current speed but had lost all acceleration (like trying to accelerate in fifth gear). It passed so I assumed that it was a blockage that had cleared.

I have driven it since and the same problem is occurring at all speeds and revs, even if I dump the clutch and flick the throttle it sounds odd however at idle it seems fine.

Often the problem will pass and the car is back to normal.

Has anybody else had this problem? Is it electrical or fuel? How much could this cost at a garage? Can anybody recommend a good yet relatively cheap garage?

[monkeyjunky]

When were the leads last changed, they'd be my first point of call follwed by throttle pots.

[glennmoore]

It recently had a full 24k service although only 19k on the clock. I believe the leads were changed then. Sorry to sound dumb but what are the throttle pots?

[mike_e]

Sounds like throttle pots. Leads and plugs should be replaced at the 24000 service.

The throttle pots tell the ECU how much throttle is being applied so it can map the correct fuel/air mixture. They are located on the front ends of the two throttle banks, small black plastic modules with wires coming out. Not expensive to replace or adjust and one of the more common problems.

Try working the throttle (ignition off) over its full travel a few times, Sometimes clears the problem.

[glennmoore]

Are the throttle pots just a case of replacing or will the car require tuning?

[dannylt]

It will need the laptop to get the pot position correctly, so back to dealer/specialist I'm afraid.

[neilv]

Just to back Danny up, my 4.5 had exactly these symptoms during an early stage of ownership, this was down to a bad throttle pot on one of the banks, this was replaced and calibrated in a matter of minutes and the problem was solved.

Neil