Hi all,

My recently purchased 1.8T 4x4 has a bit of a wierd running issue. It has a really hesitant and sometimes surgy throttle response. It isn't a constant thing, sometimes it seems to run fine, and I've noticed it is a little worse when cold. The issue is that on small throttle openings I often get a significant hesitation, like a massive flat spot in honesty, and sometimes seem to lose drive altogether for a second before it comes back in without any further input from me. Experimenting with booting it, I've also had inconsistent response and through messing around have found that it seems to have a significant throttle lag effect. To explain that, if I floor it, I get relatively little drive, but if I floor it, then back off a touch, then re-floor it the thing goes like a frightened rabbit.

So, I've been to see a friendly forum member and had the ECU looked at with Vag Com, which produced nothing, no fault codes at all to do with anything engine related.

I'm inclined to discount an air leak based on the fact that it is so inconsistent. So my presumption is that I have a slight fuelling issue. My plan of action, based on this and also on threads here is to;

Clean the throttle body

Replace the fuel filter

Possibly replace the spark plugs

Possibly replace the air filter

Is there anything else I should look at? Also, is there a thread anywhere which details changing the fuel filter, part nos etc?

For info, the car is a 2004 Octavia estate and has covered 43000 miles with full history. The coil packs have been changed a couple of days ago by my local dealer and the last service was in October last year. My average MPG with a lot of town driving is currently 29 based on 1000 miles of use.

Thanks all,

Jen.

Try disconnecting the maf and seeing how it goes

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I am currently trying to sort out a similar issue with my VRS and will be trying some of the things you have listed. Something that's worth checking that I have just found on my car is that the previous owner has fitted it with a dump valve that vents into the engine bay not back into the intake system like the original recirculation valve. This can apparently cause running issues as the ECU is looking for the air coming into the intake system which isn't there. Another thing to add to your list is to check for leaks in the vacum and breather system pipes.

Well I just drove it home with the MAF disconnected as suggested and it does seem to have improved things somewhat. I will leave it like that and drive a bit more to verify it, but I guess I'll be cleaning that as well!

One thing though, well two actually. Firstly, unplugging it has caused a warning light to come on, the triangle one with arrows around it - is that normal? Also, I would have thought a dodgy MAF sensor would flag up on the Vagcom?

Jen.

Yea that light is normal.

Couple of other things could be causing it.

- Coilpacks on there way out

- Faulty DV

- Vacumme or Breather hose split

im having to replace the Rocker breather hose atm and when i havent cleaned and re oiled my 007P it get really bad.... coilpacks are still on the list..... And this is my daily! my toy aint even finished

Don't think mafs take well to cleaning, usually people replace them, apparently only genuine or bosh will do with other makes being unreliable

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Desmojen, when my car was running like that it turned out to be my fuel pump. When the bonnet was lifted you could smell something im not a mechanic but the mechanic said it smelt lean. (Engine starved of fuel) which caused hesitation

One thing though, well two actually. Firstly, unplugging it has caused a warning light to come on, the triangle one with arrows around it - is that normal? Also, I would have thought a dodgy MAF sensor would flag up on the Vagcom?

Jen.

Normal for the light to come on, it's telling you the ASR won't work whilst maf disconnected, I think ASR uses the maf to sense wheel spin, MAF doesn't always flag a code when it's dying slowly.

The check engine light has come on as well now. I've cleaned the MAF and plugged it back in, will see if it still drives better tomorrow. Of course the lights have not reset themselves :(

Jen.

The check engine light has come on as well now. I've cleaned the MAF and plugged it back in, will see if it still drives better tomorrow. Of course the lights have not reset themselves :(

Jen.

You may find engine light might reset after learning new values from driving few miles, unless MAF is still faulty.

I have cleaned MAF a few times but won't guarantee it works. If you do end up getting a new MAF only buy OEM not aftermarket as they are rubbish.

Did you do these:

Clean the throttle body

Replace the fuel filter

Replace the spark plugs

Replace the air filter

As these are a good option certainly if you do not know when they were last changed.

Well I've done a few miles on my cleaned MAF now. The warning lights have sorted themselves out and gone, so that's good. The engine does run better, but it isn't cured.

The most annoying hesitation is still present when the engine is cold, and the full oomph is inconsistently available still. But generally a slight improvement.

So the parts have been ordered to clean the throttle body, and change the plugs, fuel filter, and air filter for new ones. I'll see how that stacks up, but I'm pretty much resigned to getting a new MAF once I get paid again.

Jen.

If you're having issues while it's cold I'd think about a temp sender as well

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Before you do anymore major component changes, have you checked all the breather hoses for holes/ splits, as they can give you that effect if they are failing.

Only takes a few minutes to check them with a small mirror and a torch once the engine covers are off. Unmetered air getting in the system will confuse the maf.

Any chance of a picture or some kind as a guide to the hoses I need to look at? There are an awful lot of hoses sprinkled around in there!

Jen.