Hi there. Can anyone help? I am having probs with my 1999 P38 4.6 auto. I seem to be getting a 'dead-band' in revs (usually between 2500-3000- revs) where there is virtually no power available - or it is delivered in surges resulting in the autobox getting confused and knotching up/ down at the wrong time.
Sometimes you could be forgiven for thinking that the autobox was stuck in gear. (and I could be wrong of course) Yet there are no transmission fault warnings on the console though - and otherwise it seems to function fine.
Engine fires up fine. Symptoms appear to be worse when 1st moving off from cold or accelerating away from a stand still. Although the symptoms are also still evident to some degree even when once warm if you are overtaking on the motorway or having to hit the gas and use 'kickdown' to overtake someone.
When moving off from cold, and when experiencing this drop in power, a dull bang or 'popping' noise (almost sounding like a backfire) can be heard from within the rear exhaust. However, If you ease off the gas though..then the revs and momentum pick up...and then you get back up to speed through the gears etc. (Same if you are already at speed on a motorway).
Strangely, if you suddenly plundge your foot to the floor...either results in...... a) no acceleration or power,....or b) you hearing the engine revs going up........yet still no change in power, nor revs counter, and wondering if the engines going to explode!....and the autobox seemingly lingering into gear. By which time i have usually eased off the gas just in case!
Other info that may be of consequence.(or not?) Exhaust system has a leak somewhere either front-mid ships - and is something I know i have to look at for next MOT anyway. CAM shaft replaced not so long back. Could either of these effect this?
Hope this makes sense to someone? And sorry for being ambiguous and vague about descriptions. Cheers,
John-o.