Just got my 8v GTI back on the road, passed MOT fine but now is suffering from poor running below 2500 revs, particularly noticeable in 4/5 gear. It's almost like the feeling you get when you take your accelerator off the acclelerator for a fraction of a second (I'm not!). Fuel consumption down by about 6mpg. Car has new plugs, oil, fuel filter -next move is to check mix but I'm assuming its okay as it passed the MOT? Any ideas out there? Help!
Tim
p.s. engine runs smoothly above 3000 revs
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Sounds like you are sucking in air somewhere. Use a lenght of small plastic pipe and listen in one end whilst searching around the manifold and associated pipes for any leaks.
Peter
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How does this work? Does a leak make a characteristic sound?
Or does it try to drag your ear into the air inlet!
Mike
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Yes there is no mistaking the noise and no never seal the tube against your ear as it cause damage to you hearing.
Have you got any constructive ideas to help the guy ??
Regards
Peter
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I'm interested in this technique and need more specific information.
What diam. plastic pipe -- hose pipe, plastic straw or something inbetween?
What is the characteristic noise of a hose with a leak in it?
Thanks
Mike
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Mike,
Its like using a stethoscope. The point is, the pipe in your ear focuses a large part of your hearing on a specific point. This makes it easier to detect the sound, and therefore source, of an air leak in amongst all the rest of the noise from an engine.
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I too think that it is air related. I had a similar problem with my MkII Gti and found that there was an air leak. Try the air lines near the bulk head, as this was the source of my problem. Listen carefully!!
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My brother, when faced with a possible air leak problem, used to spray something flammable onto the suspect bit. I think he used WD40 or lock de-icer. If there is an air leak, the spray is sucked into the engine and affects the engine idle momentarily, so you can tell if you've sprayed the bit thats leaking.
He used to do this when he suspected that there was a leak between the carb and manifold - it might work for you too.
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Appear to half sorted the problem having adjusted the mix. Mpg a lot better than before and the poor running has almost completely disappeared. Suspect that there may still be an air leak (thanks Peter) so will look for that too. Many thanks for your help guys,
Tim
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Tim,
Glad you seem to have sorted the problem. You said in your first post "assume the mix(ture) is OK as it has just passed the MOT". BAD assumption. The MOT only has a maximum for CO and HC on your car, and it is very common to find the testing garage, having found a slightly rich mixture, have then gone at the adjustment hammer and tongs ( and on K-Jetronic systems the adjustment is VERY fine), with the result that it is then far too weak to run well. BUT, as it is now below the limit, it passes.
The thoughts on air leaks are all very sound advice, but my bet is you have hit the nail on the head. Bear in mind, however, that should you have adjusted the CO too high you could fall foul of a roadside check at any time. Best to get the CO checked independantly, then.
Regards, Adam
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Tim:
I've just had a thought about this - I'm interested because I ran and liked an 8V GTI years ago.
You mention just getting the car back on the road. It's not suffering with old watery petrol from a long lay-up is it?
Andy
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I know that these Golfs (and Sciroccos) suffered from corroded fuel filler pipes. If they rot through you can get water in the petrol, as well as particles of rust which can block up the fuel lines and injectors.
If yours looks rusty, get it changed pretty soon. If not, you'll have to have the tank drained and cleaned and all the fuel lines replaced...
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Mk 1 - Yes.
Mk 2 - Plastic filler neck and tank.
Mk1s have a fuel filter though...
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I had a Mark2 Scirocco with a rusty pipe, and a mechanic I know bought a Golf Cabriolet with same problem. He bought the car off some kid who had fitted alloys, stereo, etc. but didn't sort out the rusty pipe, and then couldn't afford to pay the repair bill when all the fuel lines and injectors were clogged.
So, Robert, you're right! I think the Scirocco was based on the Mk1 Golf, and the Golf cabrio certainly was.
Sorry to scare any Mk2 owners!
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