1985 245 Turbo Intercooler runs poorly when cold - perfect when warm

[245TICSweden]

So, after a long journey, my 1985 245 Turbo Intercooler B21ET has started to run very rough when cold, it shutters/misfires really bad.

It's better under hard(ish) acceleration, but trying to maintain a constant speed at low/medium throttle is almost impossible.

Idle is okay(ish) and the car does not die, the issues starts when applying throttle.

Then when it gets warm after about 5 minutes of driving, it runs perfectly. Same when restarting after stopping for a while.

The car starts each time without issue, cold or warm. Fuel consumption is not affected. No smoke from exhaust during the rough cold running.

I've tried spraying start gas on the distributors during idle when cold, but there is no effect to the idle.

When searching around this and other forums, it seems most have issues with the car being hard to start/dying during ide when cold, this is however not my issue.

I've seen some recommendations to search for vacuum leaks, but has anyone here had a similar problem and what are your tips/experiences?

 

[TheVolbro]

My first guess is running lean due to bad warmup regulator/cold start injector. Sounds like a lean misfire on cold start that improves when the other injectors pick up the slack under increased throttle

 

[245TICSweden]

Here is a video of when I start it cold: https://streamable.com/n2q5df

 

[dl242gt]

In cold weather that is how my turbo starts. It's rough and missing like it's loaded up with fuel. Then if you keep the revs up around 1500-2k rpms it clears out after a little bit. Did you put a cam in your car? Mine started doing this after I put a V15 cam in. I just clear it out and don't worry about it. I would still make sure the control pressure is correct. That can also cause this kind of issue if it's too high or too low from spec.

 

[245TICSweden]

In cold weather that is how my turbo starts. It's rough and missing like it's loaded up with fuel. Then if you keep the revs up around 1500-2k rpms it clears out after a little bit. Did you put a cam in your car? Mine started doing this after I put a V15 cam in. I just clear it out and don't worry about it. I would still make sure the control pressure is correct. That can also cause this kind of issue if it's too high or too low from spec.

I'm not sure this is my issue and unless the previous owner has secretly installed a different cam without documenting it, I'm assuming it's standard.
It sounds mine runs on three cylinders when cold and it's really difficult to get going before it warms up.
Also, this issue has only emerged recently, previously it started really well when cold.

 

[tbrcktch]

Checked injector spray pattern, injector opening pressure, and control pressure?

 

[245TICSweden]

Checked injector spray pattern, injector opening pressure, and control pressure?

I haven't, not got the necessary tools for that.

Adding further to the complexity, today when I had the car in a garage overnight, the car started without a hiccup despite being cold...

Something related to moist sensitive electronics?

 

[bobxyz]

When did you last change your spark plug wires, cap and rotor? As easy tests, clean the inside of the cap and check that the center black spring-loaded post is OK. Next, use a water spray mister in the dark and mist over the coil/disti/plug wires and look for arcing. Bentley or the greenbooks should have resistance specs for the plug wires too.