GolfGTIforum.co.uk
Model specific boards => Golf mk2 => Topic started by: pullafacial on 04 December 2013, 20:58
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Hi guys, hoping someone may be able to help me with a problem I've got with my '90 mk2 gti 16v.
Basically, it runs and starts fine when cold.
As soon as it warms up however, it idles really lumpy to the point where it will even cut out at junctions etc.
The hotter it gets, the worse it gets.
It's almost as if the engine doesn't realise it's warm and is running as if it was on choke?
It's also using loads of fuel which would back that up.
Is there a sensor or something that I could check?
Any help greatly appreciated as I'm pulling my hair out!
Steve
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there are 3 sensors on the g/box end of head, 1 is for coolant temp guage, 1 for isv control circuit and a n other i cant remember, if coolant gauge is ok [which is red/yellow wire to one of sensors] then put that wire to the other sensors and if it stops working then that your duff sensor.
but.... first make sure timing,plugs, dizzy ok
other stuff to check are warm up regulator [wur] but you need test guage to check that
oops forgot the usual culprit of idling probs the isv[idle stabiliser valve] do this first
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Thank you, that's a big help.
I just wonder if any of the above could be ruled out due to the problem only occurring when the engine is warm?
Thanks again
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Ok, quick update.
I have worked out which sensor is for the temp gauge and used the wire from that to check the other 2 sensors. All 3 sensors make the gauge work so presumably confirms they're ok.
I've also checked the isv to make sure it buzzes with ignition on which it does.
Just to be sure, I removed it anyway and filled it with petrol a few time shaking it to empty.
Still not working! Grrrrr!
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have you checked your air filter? could be clogged solid.
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Yeah replaced that a couple of weeks ago.
I did notice a flap in the airbox that was broken.
Looked like it should be controlled by an air pipe.
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yeah that will be for the warm air feed from exhaust manifold. shouldn't affect engine running much though. well not to the extent your describing.
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Proper scratching my head now!
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try unplugging the fifth injector when engine is warm and see if that helps.
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Thanks, I'll give that a try tomorow.
What does the fifth injector look like and where will I find it?
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its on the right side of the inlet manifold near front of engine. it has a pipe and an electrical connector going to it. just un plug it when engine warmed up and see if it improves things.
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Also, bearing in mind she runs lovely when cold, is there anything else I should be checking?
Just to clarify symptoms:
Rough idle when warm (sometimes cuts out)
Bad mpg
When warm, revs seem to "hang on" a bit before dropping.
I'm no mechanic but I'm convinced it's running on choke (or equivalent) all the time.
How does the engine know when it's warmed up to adjust fuelling etc?
Thanks again
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it goes by the coolant temperature. but try unplugging fifth injector first then it will give you an idea where to look next. it might not be cutting out when it should and pumping fuel in even after engine warm up.
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Ok thanks,
I'll have a try tomorrow and let you know how I get on
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5th injector only runs on cold startup so wont be your issue. You need to get the CO% setup.
Also when fully warmed up and idling. Spray wd40 down round injectors if engine note changes your seals are shagged and its drawing in unmetered air
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5th injector only runs on cold startup so wont be your issue. You need to get the CO% setup.
Also when fully warmed up and idling. Spray wd40 down round injectors if engine note changes your seals are shagged and its drawing in unmetered air
5th injectors MEANT to only run on cold starts. there is a chance it could be spraying constantly due to a fault in the wiring. so lets not dismiss anything. very easy first test anyway.
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Yeah that would make sense to me.
Is the blue connector at the top, front, right hand side of the injector?
Also, would someone be so kind as to post a picture highlighting where I would need to spray wd40?
Phrases like inlet manifold etc are wasted on me as mechanical knowledge could be compared to that of a turkey!
Thanks again
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aye blue connector on very far side of engine, just disconnect it.
as for WD40 - just follow the 4 - injector lines from the top of the airbox down to the engine, and then spray the wd40 down in where the injectors sit
you have 7 lines in total leaving the airbox
4 for injectors
2 for warm up regulator (on side of head below distributor)
1 for cold start valve
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Thanks for your help so far guys.
Today I disconnected the fifth injector before coming to work.
It wouldn't start which I presume means it's coming on when it should.
So I reconnected it and stopped half way to work and disconnected it again.
It seemed to run nicer although could be my imagination as when I arrived at work (6 miles) it had started to run lumpy again.
Back to the drawing board, or could I have two separate issues?!?
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wd40 around the injectors when you get into work :)
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Will try this when I get home.
What exactly am I looking for whilst doing this?
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with the car fully up to temp & idling, you spray wd40 down round the injector SEALS, if they are leaking, you will clearly hear the engine note change
that tells you you have unmetered air getting in, and will not be able to set the car up to idle correctly EVER!
you are spraying the wd40 (with the straw!) down where the injector goes into the head - so down between 17 enters the head, and 19. obviously you do the 4 injectors
(http://i1173.photobucket.com/albums/r581/carmags/kjet16v.jpg)
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then once you are certain your injector seals are grand. (Also check the throttle body boot for cracks)
set about setting it up
timing
http://www.golfgtiforum.co.uk/index.php?topic=56707.0
co%
http://www.golfgtiforum.co.uk/index.php?topic=22031.0
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Cheers Gambit.
I've just tested the injector seals with wd40 as you described.
I think they're ok but it's hard to be sure as the engine is so lumpy and hunts when warm.
I've also taken the air box and connecting pipes apart to check for leaks/blockages etc.
I did find a blockage in the pipe that runs from the front of the engine to the air box but this made no difference.
Bloody thing runs fine when it's cold but gets worse the hotter it gets!
I want to set the co2 but can't find an Allen key long enough. Grrrrr!
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Nah even if it was lumpy youd still hear the note change.
Did you pull the 5th injector connector of when it was up to temp and running?
You defo need to get hold of co% adjustment tool
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Yeah I've left that disconnected for now as other than taking a bit more starting from cold, it runs the same with it disconnected.
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Also, when I took it all apart earlier, there's a bit I'm not sure I refitted correctly.
There is an elbow pipe that comes out of the back of the airbox that goes into a device with an electrical connector then connects back to the main bit of pipe that goes to the throttle body.
It seems it can be connected either way round? Not sure if there is a right or wrong way but it seems to make no difference!
Thanks again
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Thats the overrun valve. There should also be a vacuum pipe running of it to the diaphram which is on back left corner of airbox
the bit with the black pipe on it goes into the airbox. The silver thing is the diaphram
(http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/-pYAAOxyaTxRKxk5/$(KGrHqF,!k8FEM42IYkZBRK)k5fF5Q~~60_1.JPG)
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So yesterday morning it took off the over run cut off valve and cleaned it out with petrol.
It doesn't seem to fit very well stressing the connecting pipes when in place so I wonder if its leaking air and if that would cause my fault?
I also fitted new spade connectors to the temperature sensors but still no joy!
One thing I did notice on the coil is that there seems to be a spade connector fitted to one of the terminals with no wire coming out of it? I'll try and post a pic...
Another question I have is there seem to be another sensor just behind the dizzy. The wiring to that has been tampered with, would you be able to confirm the colour of the wires that should be connected to that?
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Here's a pic of the coil...
(http://i678.photobucket.com/albums/vv150/pullafacial/28C2E24F-3DB3-4FBB-AF7C-D2F31FEAE615.jpg) (http://s678.photobucket.com/user/pullafacial/media/28C2E24F-3DB3-4FBB-AF7C-D2F31FEAE615.jpg.html)
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coil is fine, you only use 3 out of the 4 terminals.
Over run cut off should all fit nicely but its tight & fiddly!
you can test your over run cut off valve & throttle closed switch easily. with the engine running, manually open & hold the throttle (around 3k rpm) then with a small flat head screw driver press the throttle closed switch - you should hear diaphram operate, revs will then plummet before immediately lifting back up
for the 3 temp senders below dizzy around water outlet:-
red/yellow wire = dash temp gauge
red/green wire = ISV
blue/white wire = ECU temp signal for timing advance
all 3 senders wires can be swapped about. so if you know the dash gauge works, then use that for ECU and try it for a bit etc
just use oil temp reading in meantime
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Hi Gambit, thanks for that.
Just spent another couple of hours reading and I've convinced myself that it's the over run valve connecting pipes. They're really loose and I wouldn't be surprised if it's leaking air there.
Would this cause the erratic idle when the engines warm and reduced fuel consumption?
I'll take the trusty wd40 to work tomorrow and have a play at lunch time.
If it is leaking there, thought I would get jubilee clips whacked on to seal it.
Thanks again
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Yeah if it is letting in unmetered air then yes it will effect idle.
Decent tie wraps will give you a tight fit on pipes. Cheaper and handier than jubilee clipping everything. Then once you find an issue then jubilee clip it!
Just rule out things one by one, and take note yourself so you can go back over things and spot potential things you may not have checked :)
Youll get there in the end, they are pretty simple engines to work on.
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Hi Gambit,
This morning I cable tied all pipes on the over run valve.
I also disconnected the engine breather pipe from the side of the airbox (which emits a fuelly smelling smoke?)
Seems to run much better now, when I change gear the revs were almost going up slightly when I put the clutch in which seems to be fixed.
Also, although tickover is still slightly lumpy, it's nowhere near cutting out like it was.
I did find a small air pipe which is disconnected down the back of the engine which I'm not sure where it should go, I'll post a pic...
(http://i678.photobucket.com/albums/vv150/pullafacial/3343DD8A-44B2-4BA2-A5B3-E9275A836A7F.jpg) (http://s678.photobucket.com/user/pullafacial/media/3343DD8A-44B2-4BA2-A5B3-E9275A836A7F.jpg.html)
Basically the pipe I'm pointing to connects under the large plastic pipe that connects to the throttle body. It also t's off and isn't connected to anything.
I guess my next two questions are:
1: should the breather pipe be emitting fuel smelling smoke and can I run it with that disconnected?
(Wondered if a fuel chAnge may help this?)
2: do I need to worry about that small pipe down the back of the engine that isn't connected to anything?
As always, thanks massively for your help!
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that could be the pipe that's meant to go your mfa on dash clocks. try blocking it of and see how it runs. there should be 4 wires going to your coil. 1 12v feed/2 wires to ignition module and 1 wire to rev counter.
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check your oil to see what colour it is? if your engine is overfueling badly your oil will be grey and watery.
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Thanks, I will check that out.
Scrap what I said earlier though, just been out for a longer run and it still idles like a dog when it's properly warmed up!
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oh there is something else I was meaning to mention. maybe the fifth injector is stuck open. in which case unplugging it wouldn't make any difference to engine running, you could try unplugging it then take it out of manifold and get someone to crank engine while you check it. there should be no fuel spraying out of it with it unplugged whether engine is hot or cold.
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Does your overrun valve have its vacuum pipes all connected? That one looks like its the one that runs to the t-piece just behind overrun valve
you can run the car with the breather disconnected but you need to plug the hole in the airbox
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Over run valve is all connected ok. This is connected to the same place the over run valve connects to just under the big rubber pipe that goes from the air box to the throttle body.
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Does your mfa work correctly? Do you get an mpg. If not then as prev mentioned itll be that.
Also check if the ecu has its vacuum line fitted. Ecu is under scuttle at driverside
there is also a vacuum line that goes to side of airbox to control the air direction flap, so that it sucks warm air off manifold on cold starts
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Mfa works (apart from cracked screen!)
Shows around 35mpg but only achieving about 24 atm.
Vacuum pipe is connected to the airbox flap. Checked the vacuum which works ok but flap is a bit temperamental.
I'll check the vacuum pipe on ecu, is it in passenger footwell bit?
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Ecu is under scuttle under the bonnet on driverside
There is a big metal bracket tci mounted to top and ecu on the underside
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Very top left hand corner of this pic behind the suspension turret you can see the plastic cover for the ecu
(http://pic60.picturetrail.com/VOL1769/7825168/17029252/263608134.jpg)