auto box I think
 

Hi, Molly (diesel auto) is being an utter pain in the backside lately.

She was hesitating like air was getting in the system not going above certain revs.

Looked at under bonnet pump, was making noises so replaced that aswell as the the intank one with items from DMGRS.

Was ok for a short while but its back.

It feels like when its trying to change from 2nd to 3rd under load its getting if that makes sense, dropping power and just not wanting to change.
I do find pulling the shifter to 2 then back to D makes her change to 3rd.

Would this be the 2/4 duty solenoid? I have done the resistance test and its giving the values in the how-to on here.

She's on 136k, plenums never been flooded since I've owned here and there is no signs of corrosion on the wiring loom at the ecu or on the twist plugs to the box.

Money is tight at the moment so don't want to have to keep throwing parts at her that she don't need.

One thing I did notice, but I was putting it down to an el cheapo elm327 was sometimes the rev readout on my phone would go nuts into the 10-13k rpm but the rev counter on the dash would be normal so probably the elm as my toaf unit don't do it.

I've just changed the 2/4 duty solenoid on my dad's 75 auto as it had failed. Done the resistance tests with a multimeter and the reading for all the other solenoids was fine but the 2/4 duty solenoid showed no reading at all.

The symptoms was very hard gear changes like as if it was banging into each gear. Even when stationary and switching to D or R it was banging into the gear and jolting the car. It still went into all gears, but very harshly.

To me your issue sounds like a possible maf issue. Try disconnecting the maf. When the maf needed replacing on my dad's 75 a few years back the car really struggled to rev in gears. Would get to about 2k and really struggle to rev higher when driving, so was also refusing to change up gears. Was surprised as usually the maf reduces power at low revs below about 2k when needing replacing. Could be worth a try just unplugging the maf.

Thanks when I'm out of isolation (7 days left unless testing ok on 6 and 7) I'll give that a go.