Starts and idles great but bogs down on the road getting worse as it warms up...

[dooglex]

My beloved 1.9petrol gearbox ate itself, I replaced with a 'reconditioned i promise' facebook special and a new clutch whilst i was under there.

Now it starts and idles great, and will take throttle on the drive. 

As soon as I get out on the road it starts to bog down more and more, and I have the feather the clutch to get it to go, eventually it wont take throttle at all, but will still idle fine as long as the clutch is engaged.
Gearbox still shifts fine if clutch is down, but as soon as I lift it the engine bogs down again.

Seems like it is OK to idle, but can't give any torque to move the van? 

Totally out of ideas, Bad gearbox? Engine? Clutch? Carb? The whole lot? Any help much appreciated! 

 

[Aidan]

Did the gearbox have oil in ? Did you change it ?

Did you do any work on the engine at all; especially fuel lines, air filter and spark plugs ?

and is the accelerator cable free and operating over full travel ?

[dooglex]

Did the gearbox have oil in ? Did you change it ?

Did you do any work on the engine at all; especially fuel lines, air filter and spark plugs ?

and is the accelerator cable free and operating over full travel ?

Hi Aidan, 

I put new oil in when I got the box, and just double checked, its filled until just under the fill plug as recommended in the book. 

I did change the fuel lines last year to switch to E10, I just fitted a clear filter in the return pipe and ran it and it was full of fuel, so looks like the fuel pump and filter etc are fine from the tank. 
Did spark plugs too last year with brand new, but tried old and new with no change. 

Accelerator is free and no problems, it idles fine and takes revs on the drive. 

Beginning to suspect either clutch is slipping as soon as I give it any throttle, i did replace it when I changed the gearbox, but maybe i messed up the installation? 
or the 'recondition' gearbox, is not in good condition, and needs work/replacement. 

[Robsey]

For me two things come to mind...

1 - Russian spark plug syndrome.
I am sure I read a thread on here a month or two back where Russian made spark plugs were going defective after barely any miles.
You do not suggest a mis-fire, but I am sure a weak spark could make the engine 'feel' sluggish.

2 - If not the plugs, it reminds me of a fuel starvation issue I had many moons ago, where my car would idle merrily all day, but needed a lot of revs (gently increasing throttle) to give my car enough balls to move.
In my issue, it was an incorrect fuel pump running at too low a fuel pressure.
In your case, I wonder if the float level in the carb is too low, or if there is a restriction in the carb fuel inlet pipe.