Mk2 1.8 idle drop

Author
Discussion

Joeigglypuff

Original Poster:

77 posts

108 months

Monday 14th November 2016
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Some may have seen me post before about this but I haven't been getting anywhere. Been driving the car with this problem for 6 months or so now and it's no massive issue, mechanic says the car looks just as solid still - but it's annoying. I have a problem where when slowing and revs falling (i.e. not in gear basically) the rpm drops to around 400/500rpm before boosting up again to where it should be around 800 (give or take 50 either side). Almost like it's about to stall, although it never does.

I've had it in the garage and checked all the hoses but doesn't seem to be an air leak anywhere. Also replaced knock, cam, crank and MAF sensors.

Final thing I've done is followed this guide to set the base idle.

It seemed to be a little low, so I upped it - but the idle kept dropping down to around 500rpm for a second then back up to where I set it at about 800rpm for 7 or 8 seconds, then back again for a second and so on. No idea what could be causing this but it seems the idle drops even when trying to set it's base setting. Any further ideas of what this could be?

Beati Dogu

9,193 posts

146 months

Monday 21st November 2016
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You could try cleaning the Mass Air Flow sensor.

Just give it a quick spray with some Air Sensor Cleaner. You can get a can of that for less than £5.

E.g.

http://www.motoelectrical.co.uk/crc-shop/crc-air-s...

Warry25

33 posts

88 months

Wednesday 4th April 2018
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Just out curiosity did you ever manage to fix this issue? In a similar situation myself and thought that changing the base idle would fix it, but maybe not.

FUBAR

17,064 posts

245 months

Tuesday 15th May 2018
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Just bought a Mk2 1.8 for some summer fun (and a couple of track days). Different issue but idle related....

Cold start idles at 2k revs. After a run or go near the throttle car idles at 1600rpm. If I leave throttle alone for 20 seconds it'll drop and sit at circa 900rpm. Car pulls cleanly. Doesn't chunter in town, hasn't yet stalled. Just annoying as I roll to a stop and it sounds like Ive still got my foot on the accelerator. Any easy solutions?