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1990 GTI stalls when hot

2K views 3 replies 3 participants last post by  Butcher 
#1 · (Edited)
1990 GTI Digi2 stalls when hot (solved)

Hello everyone. I picked up a 1990 GTI 1.8 8v Digi2a few months ago. It would not start when I bought it. With the help of the Bentley manual I have replaced a few bad parts. The list of parts I have tested and replaced:
Distributor
Knock sensor
Ignition coil
Ignition switch
In tank fuel pump
Replaced the factory ground with 0gauge cable.


Everything else seems up to specs. With all these new parts the GTI was running like a champ. I test drove it a few times about a 20min drive. The problem I am encountering is the car will start after reaching operating temps, but will die out within a few seconds. It doesn't matter if I rev the engine up, it will always die. The car will not stall if its a cold start, and will stay running as long as I don't turn it off.

I took the ISV and discovered it had oily residue inside and in the hoses. I cleaned it out, but still stalls when hot. I have not measured fuel pressure yet, but that is my next stop.

I have also noticed that the ECU relay #32, Load reduction #18 and fuel pump #167 get extremely hot. I can't hold on to it for more than a few seconds. Is this normal?

I hope this video works:
https://drive.google.com/open?id=1-ffVrY_UsRMnj67SmAzNiBzrEXNJogIs


Using the Bently section 7.4 electrical test, I have tested all except the hall sender, knock sensor and o2 sensor. Everything was within specs expect the intake air temperature sensor. It was showing a higher resistance than the diagram. I doubt that would be causing my stalling issue.
 
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#2 ·
I finally figured it out.
It was a mix of a bad CTS and ISV. I had replaced the blue sensor with a cheap Meyle sensor. Bad idea. I swapped it out with a used OEM VW sensor and so much better. I plan to buy a new OEM soon. I figured the ISV is bad because my car would surge at idle and the RPM's would drop rapidly when letting off the throttle. They would drop to 400-500 and suddenly rev up to stabilize. It would make the car shut off at idle at times and when the engine was hot all the time. I simply unplugged it and the car has not stalled once. I will replace it eventually but for now I'm good.

I hope this helps someone with a similar issue.
 
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