Help with a modified B230FT stalling

[yambox142]

Okay folks, I don't usually ask for help here but I have reached the limit of my knowledge.
I have a 1971 142E (not important) with a 2.3 liter B230FT (from a 1993 940) M46 trans swap.
Modifications:
- iPD turbo cam
- TD04-19T ← this is new (still need to truly break it in, boost is set super low)
- Larger intercooler
- Upgraded fuel injectors (newer Bosch design for improved atomization) and fuel pump (high flowing).
- Tuning chip (not the stage 3 chip, where you need the “big greens” and 3 inch MAF)
- Cone filter (brand new)
- 3'' down pipe (running a straight pipe at the moment, haven't gotten to the exhaust yet).
Replaced/Cleaned:
- Distributor cap and rotor
- New oil separation box and all associated hoses.
- MAF cleaned
- New plugs
- Replaced almost every hose in the car
- Throttle body cleaned
- Reset the ECU, more times than I can count.
Diagnostics:
- Smoke test (smoke leak from the throttle body spring and base of dipstick)
- Boost leak test (I only get air from the dip stick, when I pull the dipstick and plug the hole I don't hear air leaking form any other location. When I release my finger from the dipstick a whoosh of air comes out.

My car starts without any issues, idles fine (wideband reads 14.1- 14.5), and feels great when accelerating, BUT when I abruptly take my foot off the gas from acceleration the engine almost stalls, or completely stalls. The car idles fine, it drives so strong I just cannot figure out why it keeps stalling. The next part to be replaced is the “idle air valve.” I feel like I keep replacing parts but I get no closer to solving the problem. My love for this car is starting to turn into resentment.

Any suggestions would be appreciated.

[Laird Scooby]

Are you still using the original analogue speedo? Is there any speed sensor for the ECU to read road speed?

[Rversteeg]

Did you check the setting and function of the Throttle Position Switch? If the ECU is not aware that you have taken your foot off the gas it might be too slow in responding / anticipating by opening the idle air valve. The engine speed then drops below 800 rpm (to around 500 tpm if the throttle has been set correctly) before opening the idle air valve.

[TonyS9]

Thats exactly the fault you get when the dump valve isn't working.

What have you done regards dumping?

[mhuk]

I had the same.

Car does not like dome filter

Recirc valve has split? One vac line from recirc valve to inlet only.
Having had the same as you before I then went recently and attempted to tidy my vac hoses. What a mistake. I need up stalling .

[yambox142]

Update.
First off, I want to say thanks for all the suggestions. I did everything that was suggested here and I am happy to announce that the stall is no longer. I dialed in the throttle body (it blows my mind how precise this engine needs the throttle body to be, and the task of getting the throttle plate / switch just right was not hard, once I read the convoluted instruction ten times). After the throttle plate / switch adjustment the stall mostly went away.
When I took apart my CBV (I believe it was referred to as a dump valve) cleaned/lubed, things got even better. Finally I received my new Idle Air Control Valve (and associated hoses) and the beast was alive. Thanks again for all the help.

Yam

[Clan]

Originally Posted by yambox142

Okay folks, I don't usually ask for help here but I have reached the limit of my knowledge.
I have a 1971 142E (not important) with a 2.3 liter B230FT (from a 1993 940) M46 trans swap.
Modifications:
- iPD turbo cam
- TD04-19T ← this is new (still need to truly break it in, boost is set super low)
- Larger intercooler
- Upgraded fuel injectors (newer Bosch design for improved atomization) and fuel pump (high flowing).
- Tuning chip (not the stage 3 chip, where you need the “big greens” and 3 inch MAF)
- Cone filter (brand new)
- 3'' down pipe (running a straight pipe at the moment, haven't gotten to the exhaust yet).
Replaced/Cleaned:
- Distributor cap and rotor
- New oil separation box and all associated hoses.
- MAF cleaned
- New plugs
- Replaced almost every hose in the car
- Throttle body cleaned
- Reset the ECU, more times than I can count.
Diagnostics:
- Smoke test (smoke leak from the throttle body spring and base of dipstick)
- Boost leak test (I only get air from the dip stick, when I pull the dipstick and plug the hole I don't hear air leaking form any other location. When I release my finger from the dipstick a whoosh of air comes out.

My car starts without any issues, idles fine (wideband reads 14.1- 14.5), and feels great when accelerating, BUT when I abruptly take my foot off the gas from acceleration the engine almost stalls, or completely stalls. The car idles fine, it drives so strong I just cannot figure out why it keeps stalling. The next part to be replaced is the “idle air valve.” I feel like I keep replacing parts but I get no closer to solving the problem. My love for this car is starting to turn into resentment.

Any suggestions would be appreciated.

I assume the turbocharger still has the By-Pass valve?