Cold Start / Running Issue (with video)

[3xvanagon]

1985 vanagon 1.9

Hello, I have been chasing down a cold start / running condition. It's a odd one, if you start it and don't touch the throttle, it will idle fine. When you blip the throttle while cold it begins running very rough and often stalls. I have went through the Bentley and tested all sensors with multimeter, everything looks fine, see below... Runs completely fine and idles well once warm.

Video - https://drive.google.com/file/d/1m7URbKpq6pGzBq1CkTyOCAH0BLQeTAiZ/view?usp=drivesdk

A) 1 and 7 - (battery voltage)
B) didn't complete - couldn't get the connector off the hall sender
C) 1500 ohms @ 15 deg
D) tps acted correctly
E) oxs acted correctly
F) intake air sensor acted correctly - 560 ohms
G) ground connection acted correctly - 0 ohms
H) inj 2 acted correctly 16 ohms
I) inj 1 acted correctly 16 ohms
J) battery voltage - relay appears to be working
K) temp sensor 1 - 2400 ohms at 15 deg - seems to be working correctly
L) intake air sensor - 578 ohms, unsure of how to move sensor plate?
M) fuel pump fires when 20-25 bridged
N) voltage present on cranking
O) inj 4 acted correctly 16 ohms
P) inj 3 acted correctly 16 ohms
Q) ground acted correctly 0 ohms

Recent replaced items:

Temp 2 sensor
Fuel system tank to injectors all new
Oxygen senor
Fuel pressure regulator
Many more, can't think of the rest at the moment.

I did also take the cap of the afm and probe the connections on the back, seems to be steady when moving the arm.

[zimflux]

What year van/engine? Add it to your signature so we always know.

Check throttle switches.
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84 Westy w/ 2.1 MV

[3xvanagon]

Updated original post, thank you.

Throttle switches work as they should tested and adjusted with multimeter. Also returns to idle perfectly warm so I don't believe that's it.

[3xvanagon]

Will also note that it has a new cap and rotor, plugs and wires.

[Mckinleyvillian]

hows your fuel pump looking? the pump itself, not the wires?
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so many roads i know
all i want is one to take me home

85 Vanagon GL 1.9 stick

[xflyer]

Check the auxiliary air regulator and its hoses. Page 24.28 in the Bentley. If the "hose pinch" test fails you may be able to fix yours. Remove from engine and look through hose connection. There's a shutter inside with a V notch in it. The shutter moves on a bi metal spring so it is more open when cold and closes when warm. Heat comes from internal electric heater (and engine heat), hence the test for 12 V at the connector. Check the connections in the valve with an ohm meter. Should have some low resistance. If open circuit will have to be replaced as it will take a long time to close and you will likely have a high idle as the engine warms. There is an adjustment nut on a stud so the shutter can be moved to calibrate it. Sometimes you can make the adjustment and have it open when cold. Just need to check that it closes when warm. If the hoses are cracked the need replacing. https://www.busdepot.com/049133453-56
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C

[3xvanagon]

Thanks for the suggestion, forgot to mention, I did test the AUX AIR REG... pulled it out, cleaned it with brake clean confirmed it opens and closes with freezer and oven. i do have voltage to the heating element as well, and all vacuum lines have been replaced and/or inspected.

I have also went through the entire engine compartment with starter fluid and propane to try and sniff any vacuum leaks and did not discover any at all.

A DEVELOPMENT though - I avoided until now, but I have made some minor adjustments to the idle mixture on the AFM. I went to check the reference point on the idle mixture on the AFM and noted it was turned all the way in, I backed it out three turns and the engine does idle now when cold, though it still appears to be running rough.

I think next steps for me are to take the van in to get a valve adjustment, timing, and set the AFM correctly using a gas analyzer. I read about a method to set the AFM mixture using the O2 sensor and a multimeter, however, that seems to only work for Digifant where the O2 sensor is heated/powered. In my digijet (1.9) it is a single O2 sensor, so the only way I can get voltage is by leaving the ECU plugged in, however, in that state the ECU is adjusting the mixture on the fly which makes it very challenging to set the mixture using the AFM.

If anybody has ideas of how to set AFM DIY on a Digijet please let me know!

[xflyer]

You can adjust the Air Flow Meter without an exhaust analyzer. It is a bit tedious.
Drive enough to be fully warmed up. Check idle speed with a tach. Most auto type multimeters have this function. You can use an in dash tach, but they are often not very accurate at idle. Set idle speed per manual.
Unplug leadwire to O2 sensor. See if idle speed/smoothness (or lack of) changes.
If idle is much different when O2 sensor is plugged/unplugged try adjusting the AFM screw. See 24.29-30 in the Bentley. Since you don't have the exhaust analyzer, set the AFM screw for a good idle. BTW you don't need that box on 24.29, a regular timing light works fine. Then reconnect the O2 sensor. If the idle changes a lot. Keep going back and forth; disconnect sensor, adjust AFM, reconnect sensor. Until it does not change much either connected or disconnected.
Then test drive for overall performance. On some vans you need to shut the ignition/motor off to make adjustments as there is a memory in the ECU for the idle. This is mostly the DIgifant 2.1, but it might apply to some of the DIgijet 1.9.
You may need to fiddle with the AFM adjustment. Say, move the screw 1/4 turn and then test drive. Then when it seems OK warmed up need to check when cold. The ECU ignores the O2 sensor until the engine coolant reaches a certain temp (150 F IIRC) so the "cold" performance is controlled by the AFM screw and the map in the ECU.
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C