VW Golf Mk2 Owners Club

Rough cold starts

August 11, 2025, 07:16:33 PM

Hey,

Got a digifant 8v. Car was fine but in the past couple months has started to struggle to start. Often it starts and it's super rough, sounding almost like it's cammed, sometimes it's even so lumpy that it cuts out. Once it cuts, it really struggles to start again. Once it is running and has had a few moments for the revs to settle, it runs perfectly fine, and once it's hot will start again no problem.

There's nothing obvious. I'm going to clean the ISV out and see if that helps (checked and it's definitely still working), but if it doesn't i'm not sure where to start looking next. If anybody's got any ideas, i'd love to hear them.


TIA!

Re: Rough cold starts

Reply #1 – August 12, 2025, 06:54:12 AM

Could be the blue temp sender.
It lets the car know when it's cold, to enrich the fuel etc.
Next time, try unplugging it when you're having issues.
If it does turn out to be it, don't buy a cheap one, there's a lot of dodgy pattern ones floating about on ebay.

Re: Rough cold starts

Reply #2 – August 12, 2025, 04:46:05 PM

Blue temp sensor is a good starting point. I would get one made by hella. Failing that check all the vacuum lines for cracks and the hoses from isv to the manifold and the crankcase breather including the rocker box bung to the inlet manifold.

Re: Rough cold starts

Reply #3 – August 14, 2025, 10:49:21 AM

Thanks for the advice. I haven’t had time to clean out the ISV yet but I did quickly check the blue temp sender.

The car is turning over a lot not too before eventually starting and running rough for a few minutes. I unplugged the sender to see what the start was like and it started pretty quickly but the idle was very erratic. Plugged it back in and I’ll settled immediately. Does this suggest a functional sender?

I guess my next steps will be CTS and O2 sensor?