Hi All

I'm new to the forum and thought I would register to try and get some advice from some of the more technically knowledgable (than me!) folk on here.

I have a W reg 1.4 MPI engined Polo that wants to cut out (revs drop off) when you try and apply a bit of gas with the car sat still and in neutral. It also struggles to gain revs when on the move when you are using a higher gear than at lower revs for example. If you are sat still and in neutral then try and floor it (gas) then it will invariably just stall. It does run fine once it's past about 1000 rpm though!

Having done a bit of research I have gone about replacing various parts as follows:

crackcase breather unit

oil breather hoses

brake servo hose (probably not related but it was noted as being split when changing the above so it got replaced too)

Throttle body cleaned (not replaced) but it wasn't very dirty at all

All 4 HT leads (one was seen arcing out on the body of the part it connects to ((coil pack???)))

Temperature sensor

Fuel filter

Oil filter, air filter and oil all done as part of a service a week prior to the above)

All the parts that have been replaced have been replaced with brand new genuine VW parts.

Not that I can swear to it but I think the problem is worse when the weather is wet which leads me to think that it might be coil related but the replacement part is £90 so don't want to change it unless I am confident that it'll resolve the issue.

A friend mentioned that it might be possible to set it up by connecting a laptop to it and thus resolving the issue and another mentioned that these engines suffer with chain guide wear but on the other hand I think it is a cam belt not chain (can anyone confirm this?) and I have had another friend advise that a laptop will only diagnose issues not change 'settings'.

I am at a crossroads where I don't know which way to turn so any help would be greatly appreciated before I end up spending more on parts than the old beast is worth (probably already done that I know! lol)

Many thanks

New boy Nick

Edited 31 October, 201213 yr by skunklook

Hello Nick, welcome to the Forum,

When you say 'connect it to a lap-top', what you require is some software called VagCom (as well as the connecting lead, of course) There are different levels of VagCom, your friend is correct as far as the cheap/free version goes, it won't allow you to make adjustments, but is still worth having, as it can pinpoint many faults.

You may well be on to something when you say that the problem is worse when the weather is damp. Also when you say that there was noticeable arcing at the ignition coil, it is quite possible that, once there has been a flashover on the hard plastic that forms the connection, it can become permanently carbonised, leaving a tell-tale mark that looks for all the world like a pencil line.

I would suggest that you have a look at the coil in the dark, quite often you can see sparks where there shouldn't be any when it is dark.

Try cleaning that part of the coil and applying a little furniture or car wax to the area. This is NOT a permanent cure, the only cure is replacement, BUT at least it would allow you to confirm your suspicions.

Don't waste your money on patent sprays (Dampstart etc.) at there best, these too are only temporary.

Regards.

Hello Nick, welcome to the Forum,

When you say 'connect it to a lap-top', what you require is some software called VagCom (as well as the connecting lead, of course) There are different levels of VagCom, your friend is correct as far as the cheap/free version goes, it won't allow you to make adjustments, but is still worth having, as it can pinpoint many faults.

You may well be on to something when you say that the problem is worse when the weather is damp. Also when you say that there was noticeable arcing at the ignition coil, it is quite possible that, once there has been a flashover on the hard plastic that forms the connection, it can become permanently carbonised, leaving a tell-tale mark that looks for all the world like a pencil line.

I would suggest that you have a look at the coil in the dark, quite often you can see sparks where there shouldn't be any when it is dark.

Try cleaning that part of the coil and applying a little furniture or car wax to the area. This is NOT a permanent cure, the only cure is replacement, BUT at least it would allow you to confirm your suspicions.

Don't waste your money on patent sprays (Dampstart etc.) at there best, these too are only temporary.

Regards.

Thanks for the advice.

The arcing I noticed seems to have been irradicated by replacing the HT leads but I will have a go at that. Are you suggesting that if there is a hairline crack or similar where it was happening that this could be allowing moisture in and therefor giving the symptoms?

Would you (or anyone else on here) think that this might be caused by a.n.other faulty component otherwise?

Oh and am I right in thinking that the car does not have a distributor and rotor arm set up????

Many thanks

Edited 31 October, 201213 yr by skunklook

Yes, you're right, your car doesn't have a distributor, but has a coilpack instead.

I found on my old 6n2 it used to hate the rain, but I learned to just put up with it.

If it's a misfire, the car computer will tell you; and you can feel it anyway. Stick it in too low a gear and put your foot down - force it to buck. The engine management light will flash until you back off - showing it's a misfire.

It's a telltale sign that your coilpack is starting to fail. A hairline crack will be hard to spot seeing as the coilpack is black..

Yes, you're right, your car doesn't have a distributor, but has a coilpack instead.

I found on my old 6n2 it used to hate the rain, but I learned to just put up with it.

If it's a misfire, the car computer will tell you; and you can feel it anyway. Stick it in too low a gear and put your foot down - force it to buck. The engine management light will flash until you back off - showing it's a misfire.

It's a telltale sign that your coilpack is starting to fail. A hairline crack will be hard to spot seeing as the coilpack is black..

Thanks. Given the responses you've kindly added guys I will try these things, but would the following lead you to think anything else?:

So if the engine management light hasn't come on then would the fault memory not record a problem? And if it had recorded a fault then would it identify the coil pack or just that there is a misfire?

Something I've not mentioned so far but if sat in neutral and idling when you try and floor the accelerator it will generally give a single backfire-like 'pop'. To me this signals that unburnt fuel is going down the exhaust, heating up and exploding which in turn suggests that there isn't enough spark in the combustion chambers. I know that it could be timing related but then surely it would run rough through the entire rev range? Also, the cambelt (I'm sure it's not a chain!) isn't that old/done many miles and there are no other symptoms of belt or tensioner wear.

Does this just back up the fact that it is the coil that's probably knackered or am I barking up the wrong tree.

Apologies, I didn't spot the model.

A hair line crack will certainly hold the moisture, but what I was talking about is not a crack as such,but merely a thin burned line down the insulation, this can be even more difficult to find than an actual crack, hence the tip about looking for it in the dark, when it MAY show up as a spark.

As said, both the moulding and the mark are black, but whereas the moulding tends to be more shiny, the tracking mark will be mat black.

The light might not come on, but it will still record a fault, if it's present. If it's a serious fault it'll flag the light, if it's an intermittent one it sometimes doesn't. Still worth getting them read though.

It will just detect that there is a misfire, but, these engines work using Wasted Spark, so it fires two cylinders at once. 1+4, 2+3 (IIRC). So you'll likely get a misfire on these "banks" of cylinders.

I suppose you could pour water over it while the engine is running and see if that makes it worse. (Or use a garden spray bottle).

Same idea, get someone to hold it that's gullible, and see how far they run when it arcs. It does sound like it's misfiring very badly though.

But if it was a consistent one (due to lack of compression), the management would flag it for surely.

Coilpack, I'm going for.

The light might not come on, but it will still record a fault, if it's present. If it's a serious fault it'll flag the light, if it's an intermittent one it sometimes doesn't. Still worth getting them read though.

It will just detect that there is a misfire, but, these engines work using Wasted Spark, so it fires two cylinders at once. 1+4, 2+3 (IIRC). So you'll likely get a misfire on these "banks" of cylinders.

I suppose you could pour water over it while the engine is running and see if that makes it worse. (Or use a garden spray bottle).

Same idea, get someone to hold it that's gullible, and see how far they run when it arcs. It does sound like it's misfiring very badly though.

But if it was a consistent one (due to lack of compression), the management would flag it for surely.

Coilpack, I'm going for.

Cheers guys...

Really appreciate your assistance.

TBH it's what I thought but £90 seems steep LOL...

The water trick reminds me of when I accidentally dropped a ring spanner accross both terminals of my old mk1 golf's battery whilst still touching it, just (LUCKILY!!!). It's safe to say that I packed up and went indoors at that point feeling like a scoulded cat!

Just try it, and if it doesn't work, take it back..