Low power when cold 05 Golf BEW

The car I have had starting on 3 winters. When it gets close to below zero outside it starts to lack power. To the point driving at 55 can be a chore and my 81 rabbit truck with the 1.6 na engine seems to have more power. Doesn't matter where I fill up. Doesn't mater what I do with the fuel filter. I have changed the MAF and swapped to my Jetta's MAF just to investigate and the Jetta doesn't have issues but the Golf does. No codes other then intermittent glow plugs which I am guessing is the harness since it doesn't always trip the GP codes (2 cylinders).

Should I hook up VCDS when it is cold enough and run some checks and if so what ones?

It had a Rocket chip tune from previous owner and since I needed to tune out the turbo sensor wires that commonly break I put a Kerma tune in and it has the same issue. Great power above zero, no power below. 3 years into it and several things changed. I did bandaid it by wiring open the air box flapper and removing the plastic behind the headlight for the cold air intake factory parts and have the grill blocked off. That seemed to help last year so I may do it again of I can't find something. Warmer air from the engine bay helped.

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Well it was a cold drive home 4 hours. No passing power but thankfully at the time of day not much traffic. I was able to maintain speed most of they way.

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Lift pump functioning?
Have you done a diesel purge for your injectors? (Asking because it helped my smokey cold starts)
Did the 04-05 lift pumps /sending units have the check valves that may need drilled out?

Lift pump works. Fills the fuel fuel filter and can hear it run. Only issue is when the outside temps are cold. Car can be operating temp and plugged in and it will still do this.

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You said you removed the plastic intake piece and wired open the flapper. The snow screen is in that plastic piece have you cleaned or removed it?

Have you checked your turbo?

Any black smoke on acceleration?

Have you checked the lower intercooler hoses and replaced the O rings or are they in good shape?

Reseated the cam and crank sensor connectors? (Beside the oil filter housing)

Have you checked your cam for wear?

The upper hose that connects to the egr is it tight or do you need a dog collar?

Tdijarhead said:

You said you removed the plastic intake piece and wired open the flapper. The snow screen is in that plastic piece have you cleaned or removed it?

Have you checked your turbo?

Any black smoke on acceleration?

Have you checked the lower intercooler hoses and replaced the O rings or are they in good shape?

Reseated the cam and crank sensor connectors? (Beside the oil filter housing)

Have you checked your cam for wear?

The upper hose that connects to the egr is it tight or do you need a dog collar?

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This doesn't have a snow screen, looked but I don't think the BEW has it. And snow doesn't affect only temp.

Turbo works fine and the car has plenty of boost whether cold or hot out. The boost range stays the same.

Black smoke some when warm and full of power. Can't really see when really cold but I think the typical white smoke cars running in very cold weather is all I get when cold. Don't think it would be black when cold in my case since it has boost but lack of power would point more on the fuel or something controlling the fuel. Like a sensor. But only thing that would do that is the MAF and I have replaced that and swapped with a none good from the jetta.

Don't think the o-rings are an issue as I still have boost same as when warm.

I have the dog collar. A must on the BEW.

Cam - I already replaced when I bought it and it had the issue the whole time. The previous cam wasn't bad but just starting to show scratch marks.

Egr is capped and removed and tuned out. Has been since I owned both under rocket chip and kerma tune.

I haven't done the cam and crank sensor plugs. Would this happen during cold? I can as I plan on working on it Sunday some.

Is there something on the vcds I should look at? Cam timing maybe towards the end of range? Can't remember where that was at after the cam and tb replacement. Any numbers to look at when running and cold vs warm?

Thank you.

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Still in need of help.

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Black smoke on a Pd is a likely indication of some kind of small boost leak, or maybe a failing MAF.

The cam timing is called torsion on the Pd and should be in group 4 (I think). It should be set somewhere around 0.0, mine is currently at +.05. Different cars have different sweet spots on the torsion. Anywhere between -1.0 and +1.0 is usually a safe bet.

One word of caution if your torsion timing is waaay off it defaults to 0.0 so it’s possible to see what you think is perfect and be so far off the car has a difficult time starting.

What does your intake air temp read? Have you pressure tested your charge air piping? Are your cam and crank sensors reading? I also agree that if your torsion value reads 0.0, it's out of spec.

Check all the temp sensor values, make sure they are all very close after sitting on an ambient cold engine. Fuel, air, and coolant. If the car is an automatic, check the ATF temp value as well.

Make sure the brake pedal switch is not coming active when it shouldn't be, although that would make it completely undriveable.

I see no mention of the MAP sensor. Could be something weird like moisture freezing on it and screwing up the reading, or it just reads incorrectly when cold. So it looks like the boost is correct, but it isn't. Kind of a long shot.

The ASV is worth checking. Maybe it sticks partially closed when cold?

When the torsion value is far out of spec, the car will run badly regardless of temperature. I've played with adjusting that a lot. So I doubt it's that.

It sounds like the engine lacks power when the weather is cold, even when the engine is fully warmed up, right? So it has nothing to do with engine temperature, it's more about the air temperature that's coming in.

If nothing else seems to fix this, I'd consider doing a compression check. If engine compression was very poor, maybe fuel doesn't burn well when the air is cold. Low compression would mean the air doesn't heat up as much when the piston compresses it. Warm air might heat up enough. Cold air might not.

It does not sound like a low compression issue to me.