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Mk4 golf, rough idle and sucking in gunk

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Dec 19, 2014, 6:02 AM

Post #1 of 4 (958 views)
Mk4 golf, rough idle and sucking in gunk Sign In

Hey people,

Just as soon as I've got rid of one car and got another, I've got a problem with it again!

It's a mk4 Golf, 2001 1.6L 16v. 110K on the clock

I bought it from a dealer just over a week ago and it was taken in part exchange so I got a fairly good deal on it.

It looked in decent nick and drove quite nicely on the test drive, it has got all matching Firestone tyres throughout too, even the spare so I thought this was a good inclination that the previous two keeper had looked after it, along with all the service history.

Anyway, when I got the car I gave it a bit of a service like I always do when I get a new motor, the oil had just been changed on so I put a new air filter in, replaced the spark plugs, put some oil additive in along with some fuel additive to help clean the old girl out.

I also took the throttle body off to give it a good clean because the revs were jumping up and down a touch when idling. done this in my old mk3 Golf and it sorted it out.
The underneath of the throttle body was absolutely caked in Sh!t, a black greasy soot, I've never actually seen anything like it and took a good while to clean it out. inside the intake manifold looked like it had a lot of crud in there too.

Anyway, I cleaned the throttle body and what I could of the intake (without stripping it down) and put it all back together.

The revs are still bouncing up and down on idle and it seems to me like it doesn't have as much power as it should, it also seems like the speedo is out. I've tested it against a satnav and two phones which were all reading the same speed. so when I was doing 90 in my car (which really didn't feel like 90) it was actually 70mph. quite a difference!

I took the engine cover off of the top of the engine which houses the airfilter and has a breather pipe thing going into the box too.

The breather pipe was/is covered in gooey mayo grease. not a good sign anywhere if you ask me.

The came with a 30 day warrenty so I took it back to the garage where I bought it from, they said I would have to leave it with them. later that day, the sales man/receptionist (nob head) told me that the engineer couldn't find anything wrong with it, had plugged it into diagnostics and found no faults but did admit that it didn't seem right.

I'm thinking that they either couldn't actually be bothered to look at it properly or they found a big fault and didn't want to fix it because it would have to be done for free. Maybe not, I just got that sort of vibe from them...

Does anyone out there know what could be wrong with it?
I've got a feeling that it's sucking in a load of Sh!t and cant sustain combustion properly so injects a bit more fuel in to compensate, hence the bouncy rev counter at idle...

The car is alos fine once started up but gets worse at running temp. I've also driven it without the airbox on for a short distance and the idle seemed to handle it a bit better..


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 19, 2014, 6:44 AM

Post #2 of 4 (950 views)
Re: Mk4 golf, rough idle and sucking in gunk Sign In

This sure didn't work out on many fronts.
First, if this came with a warranty did you read what it covered and who is responsible for the warranty the dealer or another party?

Too late now but all used purchases you should at your own expense have a vehicle checked out independently of the place that is selling it and before any money changes hands with seller making it contingent upon that inspection.

You added whatever solvents to oil and fuel many of which can cause total harm quickly and if I was the seller that would void anything to do with the engine warranty never mind you took it apart some. Oooops. Now who's problem is it? I say yours and not a judge to the case but seriously how can seller warranty something you messed with?

Speed registering wrong speed? Not sure but if tyres are a smaller size than what the car calls for it could be that far off. Tyre size(s) should be on a label on either door jam or perhaps inside glove box or somewhere listed if even in the owner's manual only which any car should have unless it was tons older or a purchase to totally fix up as a known problem car that you wanted anyway.

You took it back and had to leave it: Fine but then said it showed nothing wrong but they admitted it wasn't right suggests they probably only ran it and did nothing else just making it difficult for you IMO as a beginning to not do anything under warranty if they can drag this problem out till it expires and be done with YOU and the car.

Even dealers don't want problems but the used market is just that and not all problems may be found or known by them giving only so much time to buy it to resell it with hopes of making some money at total risk if they are playing fair and legally for your rules/laws on used vehicles from a dealer.

Can't know right now as it ran well you said for a test run before you bought it if problems are from you messing with it or were there already?

Not sure what you can do with this place but this engine doesn't sound healthy now for whatever reason and about now I'd try to deal with this place for another shot at another car hopefully getting the money on this all towards the next.

It's opinion only on my part. You are starting off with a mess quickly like this so either they knew it (totally bad acting dealer) or unknown by then and you and seems this warranty thing wasn't really well written and bet if you read it that it mostly protects them,



Dec 20, 2014, 1:36 AM

Post #3 of 4 (930 views)
Re: Mk4 golf, rough idle and sucking in gunk Sign In

Tell me about it!

I don't think theres a massive problem with the car and the warranty only covers complete failure of vehicle, pretty much.
So that side of things isn't really an option, or an issue.

I think I've found the problem for the gunk though...
I found a couple of forums where people have had similar problems. It's a build up of oil from the crankcase breather where oil vapour gets caught and should go back into the system but gets clogged up after time. Bearing in mind the car is 13 years old and has done 111K there would probably be a fair build up of crap in there...

Links deleted ........... not allowed

There's a couple of links to the forums, if anyone has time to have a quick look and share their opinion that would be great.

(This post was edited by Hammer Time on Dec 20, 2014, 5:48 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 20, 2014, 4:55 AM

Post #4 of 4 (922 views)
Re: Mk4 golf, rough idle and sucking in gunk Sign In

I didn't remove them but someone will remove links to another forum. It doesn't matter if this is common as a problem for this car you should and people should be taking care of them so problems don't happen OR if all of them fail like this it's a recall or a lousy design from the beginning.

This goo up into air cleaner isn't a good sign. No telling now how long or exactly why. Could be oil change neglect, blow by of a worn engine, head and or other gaskets and more but could be an engine killer.

You seem to have found all kinds of info about what this might be, messed with it and just a couple weeks into this car having no luck with the car or the dealer. Said first time this was a mess.

This site is mostly US and Canada and the car TMK isn't sold here exactly as it would in another country IMO so at a loss for any specifics but don't need them. It's freshly purchased with a warranty and isn't running properly, you messed with it and dealer doesn't want to (it seems) do anything for you about it nor whatever warranty going to help - depending on what the reads like.

No joking. If you bought about anything and messed with it how or why should the seller take any responsibility for what happened? I don't care if this was a toaster for bread you took it apart and it doesn't work right so who would you now blame?

Vehicles are their own problem new or used with warranty and what problems might happen and who takes care of it. If your area/country demands a dealer of any kind for vehicles have a warranty on them you should have read it. I would think you could also sell a vehicle stating in writing there is NO WARRANTY at all and you are buying this "as is" or with problems totally at your own risk.

If I were stuck in your place right now I wouldn't be looking at how to fix this (with problems described) but rather how to get out of this sale if you can now as time is running out. What are your rights as a buyer of a vehicle by a dealer in vehicles (I hope was a real dealer) by your laws? Certainly private sales would or should have different rules/laws about vehicles especially.

If you have some time and more money have another shop diagnose it now if that's a possible plan to help?

Repeat - This is a mess! You do your research on a vehicle BEFORE you buy it not after. This is all being done backwards and that's all I can say is to find out what you can do for the fix or get out of this sale and start over with something else,


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