2l engine auto gearbox woes help/advice please

My son bought a project T25 during lockdown with a 2l air cooled CU engine and auto gearbox. I think the auto box is the same late bay version, maybe 010 code.

Anyway there is a serious issue in that while the engine revs well when stationary, when in drive and on the road it runs very very slowly at no more than 20mph with pedal to the floor and the engine seems to be revving slowly and its a struggle to get up hills even when in first gear.

The auto box has clean red fluid up to the mark but we haven't changed the oil or filter yet, its as it was when bought.

The engine starts and runs now after a struggle to get it started but maintaining idle speed is erratic but better than it was.

Out on the road when stopping at traffic lights the revs die and only recover when taken out of drive.

The solex pdsit carbs seem to have an idle adjustment screw on the left hand side carb looking down on the engine, which we have tweaked with not much success, used the Haynes manual, it idles quite well until we put the auto box in drive which lowers the revs and need to use the pedal to prevent the engine dying.

We would appreciate any help and advice.

 

Is there a vacuum hose associated with the autobox that may have come off?

 

There is a setup procedure for the idle mixture as you found - basically making sure the engine is idling on the idle circuit then setting the idle up.

It looks like for some vehicles the throttle linkage should be connected via the gearbox, not straight to the pedal at the front. Maybe somebody has bodged it because of unobtanium parts.

Lacking power - as usual look for leaks in hoses - idle circuit hose.
Do the pulling spark plug leads one at a time test - check the revs drop for each cylinder by the same amount.
Do a compression test, check all the cylinders have about the same compression .

 

The Pdsit carbs are fine when set up correctly but need to be adjusted by strictly following the correct procedure, random fiddling is almost certainly doomed to failure. However there's no point in looking at them until every thing else has been checked such as timing, tappets, air leaks, etc., the carbs should be the last thing in the list. To get them properly synchronised you will need an airflow meter too

 

The attached may give some help. If it's an 010, there's no vacuum involved. It all works on engine speed. On the T2 there's a cable coming from the pedal to the box then a solid metal crank to the carbs.
I can't tell you much about how to fix it, but my auto got progressively worse until there was no drive. I had to get it professionally serviced at considerable expense. But first of all have you checked the fuel solenoids are working especially the larger idling cut off on the left hand carb?

 

You might have a problem in your torque convertor

 

When driving up the hill, the engine revs were low even though the pedal was fully floored. I am trying to understand what is controlling the revs, I am assuming its the torque converter doing that. We tinkered with the pdsits just to keep the idle up so the engine wouldn't keep stalling. We are familiar with the pdsits and have a carb balancer and compression tester. We did remove one spark plug which was very sooty.

Both chokes are working correctly. My son did buy the van as a project Devon Moonraker to replace his other aircooled hightop with rotten body but good engine and manual gearbox.

The auto gearbox is new to us and we are needing to understand how it works and what the faults are and how to fix them. So any ideas or suggestions are most welcome.

 

There is a stator in the torque convertor (the other bits are impeller-Engine, and turbine-transmission)
The stator locks up against a one way clutch when you accelerate to give you an hydraulic advantage (cause the transmission ratios are high)
It freewheels when you're up there cruising.
Maybe that's where your problem is if your engine is doing what it's supposed to at idle and rev air/fuel ratios are ok.
I don't know, you are thousands of miles away (I would have said kms but I don't think you guys like them)

 

The gears ( sort of ) control engine speed , are you sure it’s not stuck a high gear , have you tried doing the gears manually?

the idle needs setting correctly first , best method ideally is start with the carbs off the engine and set them to the book , adjustable the idle speed only using the screw on the left carb, have you got the factory air filter etc ?

 

..it also sounds like torque convertor issue to me..it does things like that when its on the way out..


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Stock pdsit carbs with stock factory air filter and vacuum lines. Re bypassing the auto gears and selecting manually, how is that done please.

 

just put it 1st instead of D and then 2nd etc

 

Have either of you dropped the pan and checked the filter and oil for residue yet?
From what little I know, some tiny black deposits are normal, but big chunks of clutch in the filter may indicate other issues.

 

Is the engine running on three cylinders? It would rev with no load but wouldn’t have much power.

 

So best to identify if it’s an engine lack of power or a transmission issue first. Does the engine rev up freely when in park or neutral ? Is it firing on all cylinders & running smoothly? If not have you done a compression test?
If you lock it in 1st gear.rather than D & floor it on the flat, does it accelerate ok up to 30mph or so? Even if the torque converter is locked up it should pull ok in 1st gear once it’s rolling & above 10-15mph.

 

I know a very helpful auto transmission repair specialist in Barnsley who would take a look at it for you.

 

No problem. Let me know I’m sure they will be able to diagnose it for you from a quick test drive. They have been in the auto box repair business a long time & know there stuff