Hi and thanks for reading,
I have an intermittent loss of power which is slowly getting worse.
It can happen at any speed in any gear (manual gearbox) but it doesn't happen while idling.
The loss of power is sudden and often creates a surge that can make the car kind of twist in an anti clockwise direction and sometimes causes me to be pitched forward against the seat belt. The power of the surge is greatest when accelerating and very mild while cruising.
It may not happen for days at a time then suddenly starts.
These surges in power used to last for about a second but are now becoming longer, maybe 4 seconds, enough to slow speed down each time by 4-5 kms an hour when doing 100. The surges can occur every few seconds or over longer periods. There is no pattern of frequency.
The curious thing is that I have noticed during the longer periods of loss of power is that the tacho shows the engine revs as being constant and when I push the clutch in the revs drop and then I can freely rev the engine, I can feel it and see the revs rise and fall on the tacho.
Any clues?
Thanks in advance...Peter

IF EFI
look at the distributor plug in at the dissy
look for broken or corroded conections
the dissy /rotor cap
the coil and the exciter next to it
fuel filter

If carby add to the check list
vaccume lines dissy advance
or second stage dashpot


there is a diagnostic plug near the coil

http://i253.photobucket.com/albums/hh59/magnabuff/tp_diagnostic_plug_161.jpg

http://i253.photobucket.com/albums/hh59/magnabuff/tp_diagnostic_chart_597.jpg

thanks for your reply. haven't looked at the car yet, i'll let you know how it goes. much appreciated

sounds like a dangerous problem this surging
and loss of power at speed
hope you get it sorted
If your caris injected
it may be the air flow meter in the intake filter
:hmm:

the loss of speed isn't too bad, similar or maybe a bit worse than turning the engine off. it never stays 'off' for more than 3-4 secs. it is fuel injected.
i'm pretty clutsy with cars, my first car was an fb holden and could work on it but anything much later and i'm lost.
any clues where the intake filter is and what i might be looking for.
thanks again...peter

this may help

http://i253.photobucket.com/albums/hh59/magnabuff/EFI.jpg

Air intake leak. Check that your air hose is connected properly to the intake plenum and to the air filter box. If there are any leaks un metered air will be getting into the plenum and the MAF sensor will be getting a false reading.

This can cause surges of power or loss of power while driving.