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Model specific boards => Golf mk2 => Topic started by: TomSan on 28 June 2014, 10:06
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Hello fellow GTI fans. I've got a MK2 8V Digifant, 1990 reg with a 92k on the clock. It's been kept in good condition and passes it's MOT every year - but I have a problem I cant solve. Any help with this would be appreciated.
When starting from cold, the idle will struggle to get above 800rpm. During the winter, it was much worse and the idle would sit around 400rpm. Cut out's would ensue and so I barely drove it all winter (not good). During the warmer months, after the engine has got nice and hot, it tends to sit comfortably around 850rpm.
I have purchased a new blue temperature sensor and that made no difference. Pulling the sensor out while idling makes it sound like a tractor, so I will assume that it is doing it's job. Last year it was in the garage and they said it was probably the cold start device, but showed no interest in actually fixing it.
What else I know is that they said the CO adjuster is not working, so they had to open the unit up and manually adjust it (not so happy about that either). It did just pass the MOT with very good CO readings (but I did enhance that by having the foam filter out of the air box).
OK, I think that's about it. Hopefully someone can make sense of my ramblings and will use their mechanical super powers to help.
Thanks again
Tom
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What happens when you unplug the idle control unit? When mine went it could barely idle without stalling till warm. This might be your culprit.
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The idle was fractionally worse. Plugging the electrical cable back in made next to no difference.
Should I clean it out? Test the resistance (not sure how to)? I've heard hitting it with a rubber hammer can work :-)
Am I right in thinking this is a reasonable price to get anew one if I have to? http://www.eurocarparts.com/ecp/c/Volkswagen_Golf_1.8_1990/p/car-parts/engine-parts/fuel-and-engine-management/car-engine-management-parts/?436440160&1&fb3b7b1ab8a92997209b443e1cfd7da4eea1529a&000502
Thanks for the response Sgt!
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Does it buzz with ignition on? If so, clean it out with carb cleaner before you buy another.
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Indeed it does buzz when the engine is on, a lot louder than I ever remember it doing so. I've never taken one apart before so this should be fun - I'll update the thread when done.
Appreciate the responses!
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You could try cleaning it first, take it off and swish it out with some carb cleaner.
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With the car idling, do the revs dip/drop if you put some heavy electrical loads on? e.g full-beam headlights plus rear screen demister plus putting an electric window up (if you have these).
The idle should stay steady as a rock if the ISV is working. If you do recognise this load-dependent idle symptom, don't jump to the conclusion that the ISV itself is the problem, it more than likely isn't working because the ECU isn't getting the message that it should be in idling mode, so isn't telling it to work. It can't hurt to give yours a clean, but I doubt it's at fault unless it's really gunged up. I think you'll soon discover that it can't be taken apart in any reversible way.
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I have the same issue i am looking into. Def try cleaning the idle control first as they are very expensive. I have read somewhere that this could be an issue with the throttle control switch on the throttle body, but not sure what/where this is, im still investigating.
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With the car idling, do the revs dip/drop if you put some heavy electrical loads on? e.g full-beam headlights plus rear screen demister plus putting an electric window up (if you have these).
The idle should stay steady as a rock if the ISV is working. If you do recognise this load-dependent idle symptom, don't jump to the conclusion that the ISV itself is the problem, it more than likely isn't working because the ECU isn't getting the message that it should be in idling mode, so isn't telling it to work. It can't hurt to give yours a clean, but I doubt it's at fault unless it's really gunged up. I think you'll soon discover that it can't be taken apart in any reversible way.
Dang, full beams on really highlights that it isn't doing its job. I've taken the isv off and it looks quite clean from what I can tell from the 2 open areas. I'll spray it full of carb cleaners next.
I have read on the forums that because the isv is buzzing when idle, it is doing its job? So something seems amiss here as the thing buzzes like a... Well a buzzing thing. It will be interesting to see what borax, to see if there is other things I can check.
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Try pulling your throttle switch, that may have broken wires so the car doesn't know it's idling. The wires sit just above the manifold so are prone to cracking and throw up symptoms like this.
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As above. Throttle switch.
hold the revs just above idle by hand, press the switch in.
.revs should drop. That indicates its working.
also check the oil breather bung under the oil breather. If bad condition...can would likes its running on 3.5
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Yep, looking like a cheap fix.
With engine warm and idling, unplug the two-way connector from the top rear of the throttle body. Any change?
If not, now try shorting the two connections on the loom plug with a bit of wire/paperclip etc. Any change?
If there's no change with either of these actions, you need to continuity-check the wires between that loom connector and the ECU connector (pins number 6 and 11 here I think).
If the first action doesn't make any difference but the second does, you need to check the wiring from the connector on the throttle body to each of the microswitches, and make sure that the idle one (underneath) clicks when the throttle is closed.
Let me know if a photo or two would help.
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I shall try and give that a go, much appreciated. Isv is well cleaned out now!
If you could provide the odd pic Santiago, and it's not too much trouble, that would be great.
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Here you go. Two way connector location:
(http://i219.photobucket.com/albums/cc138/EZ_Pete/20140701_082146_zps91768056.jpg)
The contacts to try shorting together:
(http://i219.photobucket.com/albums/cc138/EZ_Pete/20140701_082216_zpse8a13a5f.jpg)
A visual inspection of the wiring coming to that connector may reveal the problem if you do find that neither unplugging nor shorting changes anything. If you still can't see anything, time to continuity-check up to the ECU connector.
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OK, so my ISV was not buzzing at all. So last night took it off and gave it a good clean. Started buzzing. Reconnected it all now the idle constantly goes between 850 rpm - 2000rpm11. I have disconnected ISV. I am suspecting blocked throttle body/butterfly?? Next job is to take off throttle body and give a good clean.
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OK, so my ISV was not buzzing at all. So last night took it off and gave it a good clean. Started buzzing. Reconnected it all now the idle constantly goes between 850 rpm - 2000rpm11. I have disconnected ISV. I am suspecting blocked throttle body/butterfly?? Next job is to take off throttle body and give a good clean.
Try what I've suggested above, in post #11, first. It's easy, it's quick, and it's free.
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So I unplugged the top connector and the engine revs to about 3000 what does this mean?
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So I unplugged the top connector and the engine revs to about 3000 what does this mean?
This means that your ECU is seeing the idle switch correctly I think.
Sorry, it was a waste of time for you, but not much time.
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I am new to water cooled engines, so it is all fun poking around. I did have a quick look in the throttle body and it is full of grit and oil, I will strip this down soon and see if it helps.
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So I unplugged the top connector and the engine revs to about 3000 what does this mean?
This means that your ECU is seeing the idle switch correctly I think.
Sorry, it was a waste of time for you, but not much time.
I did not get the same response. I got a small increase in revs after disconnecting the plug, for about a second, then they settled back down to 800 rpm. Annoyingly I searched around for ages for a paper clip - nothing suitable. I'm away for a week now so won't be able do what you said properly.
Something I did try, was turning the idle screw anti clockwise, 1 whole turn. This brought the revs up to around 875 when the engine was warm and it sounded just sweet. Also the isv stopped buzzing when the revs came up.
Really appreciate the help. I think you've got me onto a likely solution. Also just noticed I didn't follow Mr Blues suggestion properly, so I will check that again also.
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I suspect that any change at all as you disconnect the plug means the idle switch and wiring must be OK. On mine it was only when I disconnected, then shorted out the connector and nothing changed at all, that I knew there must be a problem with the wiring back to the ECU, so the ECU wasn't getting the idea of what it was meant to be doing.
Found a broken wire about 6 inches back from the loom plug.
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A little update on this issue.
I figured that due to Santiagao's advice, that ECU must be getting the message through. I did give the idle screw a full turn (anti-clockwise I think).
Now when starting from cold, the engine sits comfortably at 850rpm. After 20-30 seconds it drops down to 800rpm and sounds rough again. After driving it for a while (15 minutes), the idle get's higher and higher and sits around 925-950.
Interestingly enough, on a hot day, turn the engine off for a few minutes and back on and the rev's are right back down at 800rpm. They very quickly recover, but I thought that was rather odd. Either something is not working right or the last place that I had set up the idle/mixture got it badly wrong.
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I would imagine the time of year the car was set up would have an effect on the mix and idle as the air temp and density is different.