Hi I bought my gti on here a year ago and its been epic in almost every way possible i bought it on 107k and its now currently on 133k (high miles i know! enjoyed almost every one)

When i bought the car the engine light was on and I was told this was due to de-cat.. The car was slammed on its arse so I took the fellow clubpolo members word for it.. it still had its cat in place when i got it home and had a proper check over. Engine ran mint pulled really well through all gears as expected.

I serviced it oil + filter + sparks + ht leads + fuel filter + cleaned cda with cleaner. topped up brake fluid to max level. Another 15k no problem driving.

6 months down the line it sometimes got hesitant mid rev range for a split second then picked up as normal again after you built up 500rpm and only happened on occasion. I cleaned the throttle body out with carb cleaner. Again no problems..

Still with engine light on I had a de-cat and stainless to new custom backbox... ran fine.

Took it on a road trip to cornwall and it wouldnt start. As I was away from home I got recovered to the nearest halFRAUDS for a new battery... Using their chart I picked the 'correct battery' for the AVY. Turns out the battery was physically about an inch narrower in size. As I was away from home I thought that will do and get me home safe...

Its still on now seemingly working fine with lots of charge (sometimes leave interior light on or charger plugged in by accident and next morning starts as normal. So disregarded the size as seems to be fine.

A month after cornwall non start issue and it wouldn't start again took it to garage and got a re con starter motor fitted and ignition relay changed again seemed to run and start as it should sometimes getting slightly hesitant then back to normal. I had done about 10k so changed oil + filter +fuel filter again (didn't change plugs + ht leads)

I had a de-cat and stainless to new custom backbox november time and ran as normal albeit slightly more torque :) like 0.000002% haha

Wanting to check it was just the lambda sensor i had a diagnostics done. ready for some codes....

AVY - SIMOS 3 - 1.6l

00792 - pressure switch climate control system

16522 - o2 sensor circuit high voltage (bank 1 sensor 2)

17526 - lambda sensor 2 bank 1, lambda sensor heating; open circuit

16514 - o2 sensor circuit malfunction (bank 1 sensor 1)

16555 - system too lean (bank 1)

16685 - cylinder 1 misfire detected

16917 - a/c refrigerant ressure sensor circuit high input

P0171 - system too lean (bank 1)

P0130 - o2 sensor circuit (bank 1 sensor 1)

P0141 - o2 sensor heater circuit (bank 1 sensor 2)

P0138 - o2 sensor circuit high voltage (bank 1 sensor 2)

These were reset and engine light stayed off for a week then re appeared. took it back and it was the codes equivalent to lambda sensor the ones starting with P (I've misplaced this diagnostic sheet) so figured this was in fact due to de cat (actually think its faulty lambda sensor now)

Back end of last year I started having issues that it kangaroos on low revs in first and second...

It always threw itself into limp mode and wouldn't come out until it decided too...

I have changed coil pack new ht leads and sparks again. Still hesitant but then ran fine for a week then hesitant again.

three weeks ago I put her up for sale then It had major hesitation and the engine felt really tight then coughs and splutters as if its running out of petrol... (I thought in protest to putting it up for sale!!) so i changed the fuel filter seemed to work, It now drove about 9 miles (distance to work) with the slight hesitation on occasion then run fine full power.. this progessively got worse and worse so when i get moving I have to pump the accelerator to keep it accelerating otherwise revs drop too much... then when i get to 4500rpm it seems to pick up a lot better (not like it used to) then when vvt kicks in its back to normal power (which in comparison from really slow struggling accelerating through the revs then vvt its like vtec kicked in yo!)

This defintely got bad going up hills in 3rd-4rth at 60 to having to change down with revs just dying.

I got brave and drove to my girlfriends - 25miles. it ran the 8-9miles then coughed and spluttered and backfired on the inlet (starvation of fuel running lean) and 'ran out of fuel' it died completely (like battery is flat and wont start) then an hour later it will start as normal.

Then through club polo and other sites and plenty of google searches i decided it had to be fuel pump relay as when it cools down it allows to start up again... changed fuel pump relay (£72 from VW as GSF didnt do it) still the same symptoms..

Now in the last 2 weeks I've not driven it as when I start her up its gains with lots of tapping (again through lots of searching tappets are noisy on these and they do die down when engine warms - always keep oil topped up) then it will ping on inlet and invert popping really horrible noise. when turning off the drive I sometimes get a spring type noise (not the actual springs) best way to explain is a thud and spring noise like ba'dinnng only when pulling off my driveway with a slight incline... full lock when you turn the wheel back straight

When it dies esp light comes on - Thats the description in handbook - its a triangle and circle arrow around - bottom right of dials and abs comes on and off as it pleases. Handbrake light sometiems flashes (doesnt beep though) and brake fluid is correct level and last changed 2 years ago I have topped it up when i first bought the car...

PLEASE HELP!!!!! next port of call is to connect it back to diagnostics... My dad seems to think after changing coil pack sparks ht leads starter fuel pump relay fuel filter (3 of them in the year lol) is getting a bit ineffective and I'm like the stupid garages who keep changing parts until its solved but I just want it running as it used to 20k ago!

fuel pump works upon opening drivers door everytime you can here it priming... (possibly blocked? dont want to take tank off as that will be messy with half a tank of fuel in it...) Dad said the dreaded possibly injectors... but I'm at a loss

I generally run on V-power if I can my but my local is an esso and seems to run ok on there 95.. Try and avoid supermarkets if I can but have stuck a tenner in here and there as needed fuel until i get to my esso or see a shell...

I'm used to 6n afh engines and had 3 of them previous to this 6n2 AVY and slightly regretting the move as they were a lot more reliable and simpler! anyway please any advice or anyone had similar issues?? Am i missing something??

Where to start....

Basically the first time you got the codes read should have been before you bought the car. Simple code readers are cheap and easy to use so well worth the investment. The one I use does a bit more and does data logging etc. and I plug it in to every used car I'm thinking of buying.

Since you left it so long I would pretty much ignore the first lot of codes you got.

What you need to do instead of guessing and replacing parts is clear the codes, go for a 5-10minute drive then read the codes again. Hopefully just 1 or 2 come up. Then you have somewhere to start.

Have you actually replaced the lambda sensors at all?

Bare in mind that if you do replace anything ideally you need to clear the fault codes before you turn the car on with the new part.

Your de-cat will not be helping things. Since these have lambda sensors on both sides of the cat. I have seen you can get lambda sensor spacers that are to be used on cars with a de-cat to fool the post cat sensor but Seems a bit pikey to me. I'd rather either have a cat or get the cat mapped out properly if that is possible.

Hi kwijibo thanks for all your information.

I have taken it to my local garage for a diagnostics. I've asked them to clear any codes take it for a run then re diagnose. Should be done this morning so I'll come back to you with the codes if you don't mind. I've read about the lambda sensor spacer and followed a link to ebay and then immediately x'd they page. Always wary of electrical items from ebay. Years ago I got led number plate lights with a piggy back relay that blew all my fuses associated with the lights! No doubt lambda sensors will re appear so may have to get them replaced and re fit the cat. It ran absolutely fine to the garage (6miles) but it barely had chance to warm up I guess... (It did warm up between 70-90 as usual)

Edited 25 February, 201511 yr by rosshall22

I use http://www.ross-tech.com/ to help with codes

most point to the fact you have de-cat the car the two codes below look at fuel

I would first check for air leaks in the systems seeing why the fuel is lean.

16685 - cylinder 1 misfire detected (Check the resistance on the injectors)

P0171 - system too lean (bank 1) (Check MAP flow sensors) Leaks in intake and exhaust

I would also to a compression test just an added check.

once you found out post a solution for other people.

Just popped back to the garage and they've taken it for a run after clearing fault codes. Three have come back :

16685 - cylinder 1 misfire detected

and two relating to lambda sensors.

I then asked for resistance check on the injector for that cylinder will come back with more info!

Just popped back to the garage and they've taken it for a run after clearing fault codes. Three have come back :

16685 - cylinder 1 misfire detected

and two relating to lambda sensors.

I then asked for resistance check on the injector for that cylinder will come back with more info!

Check it across all four injector to see if their is a difference

Did a A2 with a AUA engine and we got injector miss fire on cylinder 4. tried leads plugs service etc. still the same. check the resistance on injectors 1 to 3 and it was 14 and cylinder 4 was 17 was luckily when had a spare engine and the resistance on them injectors was 14 swapped over and been all good.

Resistance of injectors should be between 12 to 15

hopefully it's not injectors as they can be expensive.

Edited 25 February, 201511 yr by residentmelon

Thanks for your input guys...

Just spoke to the garage and he seems pretty sure its the head gasket and not electrical all injectors are ok on test... he said the ping noise when it backfires is water in the cylinder not so sure on that though. and will only happen when coolant reaches a certain temp. I'm going to get a gauge to do a compression test any ideas what the AVY should be? 100psi?

BMEP
Break mean effective pressure is the average pressure that acts on the piston. The higher the pressure is, the more optimized design has been achieved. BMEP takes into account engine's volume, rpm and power output.

173.40 psi (pounds per square inch)

1195.55 kPa (kilopascals)

11.96 bar (bars)

Healthy engines should have compression over 100 psi per cylinder, with no more than 10 percent variation between the highest and lowest readings

Are you losing coolent? Also with the engine running remove the oil cap and see if white smoke is coming out this might indicate if you have a piston ring gone along with this a compression test will show problems.

The garage should also do the oil test while doing the compression test to see if it a piston ring or see if a valve stuck

Edited 25 February, 201511 yr by residentmelon

nice one for that residentmelon

yeah I had to fill coolant up with around 2 litres but never any mayo, no oil in coolant after being run for 5 mins/20mins/6miles etc...

The breather pipe is deteriating and collapsed but still free flowing for fumes. I removed the sensor (map sensor i believe) cleaned with wd and toothbrush removed quite a lot of mayo from breather pipe.. allowed to dry and refit sensor

I've removed oil cap a few times and there's the slightest whiff of grey dark smoke but dissapears as soon as i think I've seen it.

Ill be back with compression results!

Edited 25 February, 201511 yr by rosshall22

If a piston ring has "gone" you can see a lot of smoke pouring out the top.

The mayo is sometimes a mislead to head gasket failure as short journeys don't get the oil hot enough and can congeal another signs of short journeys is your breather pipe filling up with mayo

get the breather sorted as if will help keep the engine breathing freely and keep up the crank case pressure.

Sometime a head gasket can go and only let water into the piston and burn off without affecting the oil or mixing. and would experience over heating and running problems. as cylinder 1 is lean and misfiring it could be that one If that's the case I would expect the compression test to show lower on cylinder one or between one and two compared to 3 and 4.

Show us the results when you get them

Edited 25 February, 201511 yr by residentmelon

Like you are going to I would do a compression test before diving into a HG change.

How did the garage come to that conclusion?

I've seen cars with lambda sensor issues randomly misfire on just 1 or 2 cylinders throwing up misfire codes. Once the lambdas were changed the misfire was fixed too.

If the compression test comes up good I'd recommend refitting a cat and install new lambda sensors.

As stated, so a compression test first. I was led to believe the head gasket had gone on my 1.4 8v, but when I did a compression test I had 110psi across all four cylinders and had no other symptoms. It turned out that the fault in my case was a faulty HT lead that caused eratic idle but I took someone who allegedly knew what they were doing's opinion.

Thanks everyone. I haven't been able to get hold of a compression kit today but will before going for a HG change. When I bought it with engine light on he said it was showing 02 sensors (lambda) as it was de-cat - but it wasn't decat so I think Lambda sensors must have been on the way out then.

Just checked carpartgiant and they're £90 for pre-cat and £44 for post-cat

http://www.carpartgiant.co.uk/Products/Volkswagen/Polo/1.6L/Pre-Cat-Lambda-Sensor.aspx

http://www.carpartgiant.co.uk/Products/Volkswagen/Polo/1.6L/Post-Cat-Lambda-Sensor.aspx

£78 and £94 on GSF

http://www.gsfcarparts.com/parts/fuel-emissions/mixture-formation/lambda-sensor

Lambdas are the way to go if the compression checks out ok across the four... I really didn't think the lambdas would cause misfire maybe running rich/lean...

All good stuff moving forward. Roll on tomorrow fingers crossed the rain holds off!!

Thanks again guys :)

I normal work from cheapest to expensive.

Still trying to source a compression test somewhere... This is up for sale if any one wants to take on the goose chase sensible offers - i know its not in the best of shapes and hopefully will be fixed soonish but i do need a daily as this isnt reliable to take any distance currently :( swaps or p/e cash either way!

http://www.autotrader.co.uk/classified/advert/201502261255218

Edited 27 February, 201511 yr by rosshall22

If you want to buy one I got this one probably get it cheaper but if you want to do a test today is probably the best place to get one on short notice.

https://www.machinemart.co.uk/shop/product/details/clarke-cht693-8-piece-compression-tester-kit?da=1&TC=GS-040810693

I posted some compression results in this thread - message 20

http://www.clubpolo.co.uk/forum/index.php?showtopic=334294&hl=

A compression test is useful, but a leak test is more informative - however you should be closer to 170 psi than 100..

Edited 2 March, 201511 yr by 937carrera

Here's the test info and measurements from Elasawin

• ‒ → Remove cover above camshaft housing -arrows-.
• ‒ Take off H.T. wiring with spark plug connectors first.
• ‒ Unscrew spark plugs with spark plug spanner 3122B.

• ‒ → Pull 4 pin connector off ignition transformer -arrow-.
• ‒ Remove fuse 40 for fuel pump.
• ‒ Check compressions with compression tester V.A.G 1381 or V.A.G 1763.

Note:

See relevant test unit operating instructions for instructions on how to use test unit.

• ‒ Operate starter until tester shows no further pressure increase.

Compression pressure:

New: 10...15 bar
Wear limit: 7 bar

Permissible difference between all cylinders: 3 bar

I've worked constantly over the weekend and haven't had chance to go any further. Currently using my brothers corsa-c so time is of the essence! Thanks for all the info. Never heard of a leak test before 937carrera... any more info or link to a step by step? Gonna get a compression kit either tomo or weds and go from there.

Thanks :)

Leak down test involves pumping compressed air into a cylinder to a pressure of say 150psi then cut off the supply and see how long it can hold that pressure, the longer it holds the pressure the better

chers nige will hopefully get time to investigate more tomorrow!

Here's a couple of links:

http://en.wikipedia.org/wiki/Leak-down_tester

http://www.dietersmotorsports.com/Compression-leakdowntest.htm

A leak down tester helps diagnose what the problem is, without disassembly

still unsure on this leak test read the links and thinking i need a trustworthy garage to look at this for me. as I'm not confident enough to try it

I wish it would drive the 60miles to JBS autodesign. Excellent guys over there..

currently uploading a video to youtube so those with mechanical hearing can maybe help.

Turned it over and started first time tonight but sounds like a piston is loose.. again wild goose chase... will post link when uploaded...

so frustrating!

Edited 3 March, 201511 yr by rosshall22

It's always difficult on forums to judge where somebodys knowledge level is - you don't want to insult them or make them feel as though they don't know anything.

I have read your initial post again and listened to the video - she doesn't sound healthy at all. I am assuming that the hunting / backfiring is just the result of its attempt to tick over and not you moving the accelerator pedal - correct ?

The backfiring could be an fuel or ignition fault.

If you suspect one cylinder then sequentially remove the connector to either an injector or spark plug in turn. (you should probably put a spare plug in the disconnected lead and earth it). If the engine is worse, then that cylinder is OK, if it's no different, then you know you have a problem on that cylinder.

To do a leak test you need both the leak tester and a source of compressed air. Not all garages have the tester, and the advice was more about ensuring that whoever did the testing did a leak test rather than a simple compression test followed by "we'll have to whip the head off to have a look mate". FWIW I had an issue on a Saab and as part of the diagnosis offered to lend the main dealer my leak tester as they didn't have one.

I see that one garage has said it's a head gasket. You can test for that by carrying out a sniff test - a sample of the engine coolant is tested for hydrocarbon residues. It takes about 5 minutes to do, and again doesn't involve taking your engine apart.

Can you tell us what error codes are currently showing up in VCDS ?

A few things you can do to try and narrow down the diagnosis and the video was a good idea Hope that helps and i'm sure others will be along shortly