Airbox engine cover flap valve (engine pinking when hot)

Chat about your 9n Polo (inc GT and Fun)
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

After a few hundred more miles driving on long journeys, in warm (and wet) weather, I think I can safely say that widespread pinking has all but gone. Its clearer now that after a long journey, when entering local stop/start traffic pinking does occur when starting off from a standstill, as well as after the vehicle has been parked, and when starting off. The latter I thought might have been due to heat soak, but now I think otherwise. Incidentally, I did hear pinking under the aforementioned conditions (slight incline) around 1500 rpm - something I had not noticed before. Its all very minimal, and easy to throttle through to get clear revs. It sounds like the EGR could be implicated in this, either by sticking, being gummed up, or both. I might try an EGR cleaner like http://www.wynnoil.co.uk/products-wynns ... d-egr3.htm - on that well known Website....(http://www.ebay.co.uk/itm/Wynns-Petrol- ... 3a744d374d)

Incidentally, I read somewhere that EGR problems can also be due to the solenoid deteriorating as much as it being gummed up, etc. Will try the cleaner first.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

I was just checking through all your previous postings and see that you have posted again, anyway, back to why I was reading this thread, I have now replaced the MAP sensor with a secondhand one. The one removed was gunged up badly and was a Magneti Marelli T-PRT04/B dated 2002 CB - the one I fitted was a Magneti Marelli T-PRT04 - so it is an earlier build state/version - seems the "2002" means production period 20 of year 2002. Once again the cars seems to pink less - as it always does when something is changed or cleaned. I've cleaned up the original MAP sensor by soaking it in neat Redex fuel system cleaner for an hour then washed it with an IPA spray. So I'll either swop it back in or hold it as spare.

Back to your original comments about how to test the hot air flap thing, I've had a look in ElsaWin and VAG just use a freeezer spray to get it to close - you can buy these sprays in Maplin or cheaper on ebay.

I still don't think that I could say my original EGR valve was faulty or worn, still not cleaned it up though, there was a thread going in http://www.briskoda.net about worn EGR valve bodies but in that case it was extreme wear leading to the alloy body distorting and the sealing plug getting blown out.

I'm sure that cleaner stuff will do its job, its just a pity that they keep showing pictures of typical DERV engine EGR as they really know how to coke up their EGR systems.
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

I've ordered the cleaner, and will try it out the weekend after next.

I changed that 'MAP' sensor earlier (it was clogged) after a third-party service garage advised it needed replacing. Your experience suggests it might be worth taking it out and examining it as 24 months have elapsed since it was replaced.

After approx 300 miles I topped up the oil somewhere between a quarter and one third of the distance on the dipstick (between low and high marks). It might just seem this way, but it appears to use more oil after high speed driving (motorway). Or maybe I don't notice the oil consumption while driving about town (longer intervals between top ups). I'm trying to work out the oil consumption rate and wonder is the difference between the low and high dipstick marks 0.5L?

By the way, my Polo was manufactured October 2002.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

I would agree that the car uses more oil at higher speeds, do you find that the oil level is always way above the marks prior to wiping it if the car has been left overnight - ie 12 hours? I reckon that the oil level from 1/3 into the hatched area up to maximum will be 0.5 litre. I will admit knowing that if you let the level drop until the oil level warning sounds, you can add 1.0 litre without over filling the engine!

The build date for my wife's car was late August/early September 2002.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

One thing that I forgot to say was, that the MAP sensor output is a big player in what determines the fuel injection pulse durations - and I'd reckon that the response time to changing pressures will determine how close to pinking, before the timing is backed off a bit, the engine finds itself. Another thing, as my original MAP sensor seems to be an evolution of the secondhand one I bought from ebay, and there seems to be stories about a "new design" of this part is now what is sold, I'd reckon that your third party pattern part will also probably be a copy of the earlier design - even earlier than your original MAP - its just the way things are with most pattern parts. Maybe cleaning it and refitting it would be the way to go - that is what I intend to do when the weather gets hotter.
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

I'm definitely going to have a look at it next week. Are you saying there is a 'new improved' OEM part?
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

littlepolo wrote:I'm definitely going to have a look at it next week. Are you saying there is a 'new improved' OEM part?
I think I asked that question on a VAG forum after someone claimed that the design had changed - but I think that poster had had his help from the forum and was now not interested!
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

Out and about yesterday (a very warm day) I noticed quite a bit of pinking around 2000rpm, although it was not as bad as before. I have an aerosol of Wynns EGR cleaner to hand (it smells very potent) was going to give the car a treatment this week. However, with the MOT due early August I've booked it in for this Friday. Looking at the emissions test data from last year, I notice the following (limits/actual):

Fast idle test

CO <= 0.200% / 0.082%
HC <= 200ppm / 0.79ppm
lambda 0.970-1.030 / 0.999

Natural idle test

CO <= 0.300% / 0.292%

Now I know its a simple test of under limit or not, but do any of the actuals sound problematic?

I'm wondering if I blast the EGR with Wynns if its going to knock any of the emissions data, and maybe I should leave the treatment until after the MOT?

On another note, I'm going to try and mark the headlight beam adjusters before testing because some test centres seem to try and claim the beams are out of alignment. I got stuck for that last year, and could not prove otherwise. I know the state of the roads here does not help, but I'm pretty sure my beam alignment is not askew.

Back to the pinking problem, I plan to clean the 'MAF' sensor thing, and treat with Wynns EGR cleaner, take the car for a good blast, and see what results.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

Tricky one, this close to MOT its probably best that you leave things "as is" - remember that you have cleaned the TB and EGR tube since your last MOT so things should have improved. As far as I can remember, my wife's Polo was "squeaky clean" at its MOT last September.

Headlight aim, it should only fail if the beam aim is too high - if its too low it will not cause any problems for other road users.

I'm kind of thinking that my next step is to try to decoke it a bit using Seafoam as that stuff is the only "cleaner" that gets good reviews in USA - if that is anything to go by???

No harm in cleaning the MAP sensor now as that should only improve its response, I'm guessing that you no longer have the original one?
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

I read many good reports about Seafoam, but was unable to find a supplier here. I'm sure most engine in the US run up very high milages compared to here.

I have the old MAF sensor, somewhere. I think I only replaced it thinking it was at fault... it was gunged up though.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

I'd still reckon that your original MAP sensor would be a newer version than the third party one you bought - specially if it has the extra (difficult to see) markings on it - could be worth cleaning that one up, maybe leave it in Redex if you have any, for an hour or two before using the spray on it - I intended to do that but in the event the container tipped over after about 15 minutes - but it did end up a lot cleaner, I tried getting some black spots of it using an old tooth brush (handy things to save up!).

Seafoam, well initially I could not work out exactly what it was made up from with a name like that (another magic "snake oil" product?) but it seems like the name is just that - a name, its just another cleaner made up from petroleum products. It looks easy to get on ebay - that was where I was going to get it from (UK based seller).

The other thing with these VW engines is, that they do seem to get "dirty" inside - have you had a look down into the cylinders? My old VX Cav GSI was almost squeaky clean every time I changed plugs and its exhaust outlet was also not very sooty, the Polo exhaust outlet is sooty - both cars had cats fitted so maybe that "effect" is due to the Polo engine being in compliance with more modern European exhaust emissions!!

Wonder what effect the extra Ethyene (or what ever) they must add into the fuel is having on how clean engine internals keep?
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

I put the Wynns EGR cleaner in via the breather pipe on the venturi chamber. I could not find any easy way to put it via the EGR itself.

Anyway, the Polo passed its MOT this morning.

Regarding emissions, the CO levels and HC levels changed.

Fast idle CO now at 0.07, and, strangely, HC up to 161 (not sure what temp engien was at)

Natural idle CO down to 0.10

On the way home, I noticed pinking in the usual range - still, albeit less than before cleaning the plate.

IIRC the 'MAP' sensor was changed previously because a VW specialist picked up a fault on a scan. I didn't have time to take out the new sensor yesterday to inspect it. Hopefully the cleaner will have degunked it to some extent (yet it was difficult to sense that it was doing anything - no smoke out exhaust, etc.). I might have a look at it tomorrow.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

Weird the way that figures changed, though I'd reckon that it would prove impossible to repeat these tests and get the same results - though hopefully there would be a trend to support these changes from previous MOT.

I thought that the EGR system was meant to reduce the "running HC" levels - so now that your's is working surely a lot better than at previous MOT (after you cleaned the interface plate ports), I would have expected that value to improve.

I'll have to look at my wife's car's figures for last year (nearly or totally choked EGR system) and when MOT'ng it compare the results and report back.

I'm thinking of searching around the internet to see if any "pinking" trends are getting reported with increased levels of Ethylene (or what ever) is now definately in our fuel. I think that I read somewhere that petrol pumps will now need to include info on levels of this stuff. Interestingly or not, my old B5 Passat V6 now also will give a bit of pinking noise if I snap the throttle open - it never did this in the past - but this could be a red herring!!

Friends at work with newish cars with petrol engines all notice that exhaust pipes are sootier than they used to be years ago - but this could also be a red herring.

I was of the impression that the reduced pinking after cleaning the EGR system would be down to the EGR system now dropping the engine temperatures - which it is meant to do - though its main reason for that being done is to reduce some of the "banned" exhaust components, though it would also reduce the temperature of the accumulated soot/coke that would/could be the source of the pinking.
littlepolo
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by littlepolo »

I think I'll put a half a can of Ecotek through the induction system when I find time - because its lying there in the shed.

As for fuel quality, I'll dose with an octane booster - once again - and report back.

Incidentally, someone tried to break in last year and cut out the rear quarter window. I just replaced it today using a 30.00 replacement glass from the dealer, and a tube of SilkaFlex 255FC from that well known Website. I thought it would be tricky to cut out the adhesive/bond around the old glass, but it was out in under an hour. The new glass is bonding now.
RUM4MO
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Re: Airbox engine cover flap valve (engine pinking when hot)

Post by RUM4MO »

That would be a bit cruel if the car was taken AFTER you solved your pinking problems!

Wife's car needs fuel and as prices are still not back at their peak, I was planning on filling it with some higher octane stuff, blurb used to say Shell "best" was a good engine cleaner - but up here Shell tends to the dearest brand, so we'll see. I have a measured ammount of Redex ready to get added as well, but I'd reckon that that will be a waste of time as more aggressive cleaning is called for, but maybe that will get added until I get hold of some Seafoam - I might have a look to see what Halfords has to offer - ie expensive Wynns or Redex "one shot stuff".
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