Good morning all, I've got a problem with my idling on my 86 GTI and I've tried and tested a lot of things without success. Unfortunately, it has a habit of drastically dropping the idle (to around 300-500) when the clutch is pressed in or touching the throttle when sat in traffic, once it dips down it'll start to fluctuate between actual set idle speed and 300-500. It only seems to do this when the car is coming up to temperature, especially when it is either cold or wet outside. Occasionally, it'll drop so harshly and low the car will stall. It will only do this when it's chucking it down with rain or its very cold out. It's definitely less noticeable when we have hot weather; regardless of 'engine' temp. What has been done so far: Earths Checked & replaced where necessary. Fuel pressures checked and WUR adjusted (It has a 16v adjustable WUR). AAV tested, apparently this works as intended. Plug replaced due to corrosion. Leak-down and compression test. Rolling road test carried out post engine rebuild showed no issues with fueling, car makes 140bhp. Worth noting it was an awful lot worse before this tune-up took place. Timing checked and adjusted. The engine is running a Newman 268 cam, high compression pistons and has a mild port/polish. Any help or pointers would be appreciated!
Idles fine at around 1000 if not a smidge more, I've had this set up a few times so it should be okay.