Kangarooing uphill under acceleration

Hi, I've had a 1974 S3 88 station wagon for about a year - still sorting her out slowly. She runs well most of the time, but recently when starting to go uphill from level in 4th, and well before the point where I'd expect to change down, she starts kangarooing violently. Lifting off the accelerator slightly stops the kangarooing. Change down to 3rd, apply reasonable amount of accelerator (not foot flat on floor), same thing, cured by lifting off slightly. This is on a piece of road I travel regularly, and she's only just started doing this. Previously she would make steady progress uphill under firm acceleration, going down through the gears, as you'd expect. Nothing else significant has changed (e.g. vehicle load pretty constant). Grateful for any thoughts please!

Jerry

bar operated accellerator linkages ??

broken engine mount and the engine rocking badly in the engine bay

those two combined will create that kind of thing

fuel starvation,check your filters and fuel pick up pipe

petrol or diesel?

Sorry, should have said, 2.25 petrol.

fuel starvation as already posted above.
could be caused by a number of things, but to be going on with-
fuel vapourisation in the lift pump. does it kangaroo when cold? is the lift pump hot when it kangaroos?
fuel vapourisation in the delivery pipe from lift pump to carb.
stuck float in carb.
crap in carb.
blocked jet(s) in carb. (likely, do yo know what type of carb you have? weber or zenith?)
can you get it to kangaroo on demand or is it always the same place?

Mine did this when it was hot - was fuel starvation caused by fule boiling in the lines and mech pump. Firstly I re-routed fuel pipe radiator shroud to keep it cool which helped, next replaced mech pump with electric for complete cure.

Thanks for thoughts.

It's a Weber carb. Haven't had it apart yet.

The problem happens on a regular journey (to where we keep our hives - I'm a beekeeper). The problem starts as we start to go up a long, fairly steep hill about 5 mins from home, so the engine won't be that hot. I don't think the problem is connected to vehicle attitude - the latter part of the journey is up an even steeper dirt track, in 1st or 2nd, which is problem-free. Doesn't seem to happen on the level or downhill.

I swapped the lift pump earlier this year as the old one was leaking, but the problem didn't appear until several months after the swap.

Given the circs, I'm inclined to think carb problem more likely than vaporisation? But I'll also check the engine mounts this week.

Could be a problem with float bowl fuel level! You will need to remove the air filter and the screws that hold the top of the carb on, disconnect the choke flap housed in the top part of the throttle body and lift off the complete top !! Inside you will see the float bowl with fuel inside and the float hopefully floating in the middle !! The level of fuel is possibly high or low , this level is controlled by the float which operates a small needle valve ! The float allowing a certain amount of fuel to fill the bowl and then restrict flow until your engines fuel demand rises , the needle then allows more fuel in etc !! A high level will result in a rich mixture, a low level gives a lean mixture! Sometimes a good clean can be all that's needed but a new needle and seat is best !! Also blow out the two small jets you can see them in the middle of the carb !! Ones the pilot jet ones the main jet !! Slow speed faults are usually pilot jet related !! Always check the carb for leaks etc after completing any work ! We don't want to be wasting that now do we. !!!! Good luck

While you're at it check the filter in the carburettor held in by large brass nut near fuel inlet. They can get clogged, even if you have an inline filter.

Had a similar problem with my 2A zillions of years ago, and it turned out that the timing was fractionally too far advanced.

Once it had been backed off a couple of degrees, it was fine again!

is the weber a twin choke or single choke?

To answer a couple of previous questions/suggestions:

- the carb is a Weber 34 ICH
- I've checked the engine mounts and they all seem sound and tight.

Next step is to look in the fuel filters and carb.