No power under accelartion

[Kings]

Had our 1975 T2 for a while now, and since May, it has not been driving great. 
1. Started reving really high in idle once been driving for a while to the point of having to stop, seemed to get better on its own accord but just comes and goes now.
2. Been driving very sluggish for a while, will sit at 80 but struggles to get there, and surges(think that's the best term) through the gears if foot not right down. Struggling with hills more and more.
3. Today will not drive off unless pumping the accelerator. Cuts out with normal pressure on the accelerator. Starts first time and will idle OK(although a bit rough)  Took it for a drive and completely died on a uphill. Managed to get it started to turn around to head home, but even on the flat in first gear no acceleration. Also when accelerating it is back firing a bit.
New spark plugs and cables fuel filter etc fitted a few months back.
Checked all pipes and connected apart from the vacuum hose of the distributor which a few people have not been able to find a home for it. Normal place has been capped off.
Just looking for any ideas as i am at a lost, hope the above makes sense.

[Barry]

1. Started reving really high in idle once been driving for a while to the point of having to stop, seemed to get better on its own accord but just comes and goes now.
.

That, to me indicates a vacuum leak. 
Leak is closed when cold but quickly opens making a very lean mixture

What motor do you have?
Type 1 or 4

Lots of places they can leak but different between the 2 motors. 

Need more info regarding the vacuum pipe off dizzy. 
You won’t accelerate with that off

[grumble]

Had our 1975 T2 for a while now, and since May, it has not been driving great. 
1. Started reving really high in idle once been driving for a while to the point of having to stop, seemed to get better on its own accord but just comes and goes now.
2. Been driving very sluggish for a while, will sit at 80 but struggles to get there, and surges(think that's the best term) through the gears if foot not right down. Struggling with hills more and more.
3. Today will not drive off unless pumping the accelerator. Cuts out with normal pressure on the accelerator. Starts first time and will idle OK(although a bit rough)  Took it for a drive and completely died on a uphill. Managed to get it started to turn around to head home, but even on the flat in first gear no acceleration. Also when accelerating it is back firing a bit.
New spark plugs and cables fuel filter etc fitted a few months back.
Checked all pipes and connected apart from the vacuum hose of the distributor which a few people have not been able to find a home for it. Normal place has been capped off.
Just looking for any ideas as i am at a lost, hope the above makes sense.

I assume that it is a type 4  engine, a good starting point would be check the balance tube elbows on the manifolds, fuel feed and pressure,float levels in the carburettors, check the accelerator pump discharge. Check the valve clearances, dwell angle and timing, adjust the idle mixture and speed, balance the carburettors with a synchro syn. Refit the vacuum advance tube , some of these run to the R/H carburettor but most run to the L/H carburettor. Carry out the above with a vacuum gauge connected to the balance tube (this also makes it easier when the idle mixture being adjusted.)

[Oldman]

Agree with Barry (and Les), sounds like a vacuum leak but could be a number of other issues piggybacking to give you grief...
If you have a type 4 engine, check that a rubber elbow isn't cracked or hasn't dislodged from air filter box to the idle circuit .
Other common vaccum leaks include a dodgy one way valve between intake manifold and brake booster., in the engine bay...easy enough to check....undo a clamp and check the one-way valve by sucking opposite to the arrow that indicates flow....it should only permit pressure one way (hence the name  )
Brake booster diaphragm may have failed also....causes a vacuum leak as pressure is not maintained within the booster. How are your brakes ?

As with any engine diagnosis, start simple and work up. 
Check all vacuum hoses for integrity and connections, then basic engine setup.....valves set stone cold, points gap (if your running them), carb. mixtures and synch. if you have dual carbs.
A lot of advice will depend on the type of engine you have , so let us know so we can narrow down the potential options.....

[Kings]

I assume that it is a type 4  engine, a good starting point would be check the balance tube elbows on the manifolds, fuel feed and pressure,float levels in the carburettors, check the accelerator pump discharge. Check the valve clearances, dwell angle and timing, adjust the idle mixture and speed, balance the carburettors with a synchro syn. Refit the vacuum advance tube , some of these run to the R/H carburettor but most run to the L/H carburettor. Carry out the above with a vacuum gauge connected to the balance tube (this also makes it easier when the idle mixture being adjusted.)

Yes type 4, all elbows are good and connected.
Vacuum advance hose isn't connected, but not sure it has been for the past 6 months and been drivable ok. The connection on the L/H carb has been sealed.  Checked the fuel filter under the car and the outlet tube has a kink in it, guess whoever fitted it had a bit of a problem.and bent it have ordered a new one. Not sure if this would be the answer but needs sorting. Have also ordered new spark plugs and leads.  Spark plugs where pretty black, although only 4 months old when replaced.
This problem may be above my pay grade I reckon.

[Barry]

.  Spark plugs where pretty black, although only 4 months old when replaced.

Sooty black or oily black?

[DavidH]

Back in '79 my mechanic was changing the fuel filter but the bus used to die on long uphills & pumping the accelerator helped. Long story short there was another fuel filter hidden above the starter motor (what nung would put one there?) that was totally blocked. Worth checking.
Cheers

[Oldman]

This problem may be above my pay grade I reckon.

Worth reading through the Help & Assistance Section :
https://kombiclubaustralia.com/forumdisplay.php?fid=27

Particularly the  Bay Tech Clinic:
https://kombiclubaustralia.com/forumdisplay.php?fid=8
....and "How to & Handy Hints", 

Lots if proven info. in the Important Threads. at the top of each Section.

Above your pay grade ...?
You have a couple of choices 
Diagnose and learn from other's experience,( and there's lots here),  or find a reputable air-cooled mechanic and open your wallet.....wide.
It's the reality of owning a kombi unfortunately....approach it as a learning challenge.

In my opinion, getting  everything set to a reliable base line and maintaining everything in the best possible condition, the way it was originally set up, will provide you with the most reliable vehicle. If you are running the correct dizzy for the engine, the vac. advance line needs to be re-connected to the inlet manifold. The dizzy relies on the vac. advance can to operate the dizzy properly. A vac. advance dizzy without the vac. connected will always give you issues.

As has been said before, more often than not it'll be something relatively simple.....or a combination of simple things piggybacking to cause issue/s.
Good luck and please post up how you go.....it's how we all learn.

[Kings]

Sooty black or oily black?

Sooty black

[grumble]

Yes type 4, all elbows are good and connected.
Vacuum advance hose isn't connected, but not sure it has been for the past 6 months and been drivable ok. The connection on the L/H carb has been sealed.  Checked the fuel filter under the car and the outlet tube has a kink in it, guess whoever fitted it had a bit of a problem.and bent it have ordered a new one. Not sure if this would be the answer but needs sorting. Have also ordered new spark plugs and leads.  Spark plugs where pretty black, although only 4 months old when replaced.
This problem may be above my pay grade I reckon.

OK have you checked the points gap or dwell angle if you have a meter, the fibre block that opens the points wears with use?