I'm not sure if anyone can help me with this, the mechanics I've tried so far haven't been much use.

My car started suffering in December last year, as I was driving home from my staff Xmas do the car began cutting out and stalling, I had no idea why the car was behaving like this as my knowledge was very poor at this point. My mechanic diagnosed a misfire and as most places were about to close for xmas all he could do was swap a couple of coils over which seemed to do the trick and I thought the problem had been cured. I was wrong! The misfire came back with avengence in June so I took it in again and this time he replaced the coil on cylinder no.1 with a new one. This worked for about a week or so before the problem returned and so I took it in again and he swapped 2 of the coils over and mentioned something about injectors and sticky valves. Needless to say that the problem came back almost immediately and as I wasn't best pleased with the garage owner's customer service skills (it was almost like I was causing him an inconvenience by turning up with my misfire) decided to try somewhere else. I did my best to explain the situation and they diagnosed....a faulty coil! Of course.

So I've spent approx £200 and all they want to do is swap coils around, cylinder 1 is the faulty one and by this point the new coil is on no.3. Subsequently the car has been sitting idle since the end of June until I could work out what to do.

Well this weekend after a bit of research I gave it a go myself. I replaced the coil on no.1 with a brand new Bosch one (which took all of 5 minutes, I can't believe they charge £90 for that) and also replaced the injector on no.1 with a reconditioned one from ebay. I *thought* I had cured it but unfortunately as I was taking it for its MOT it came back again and so I had to cancel. The MOT has now lapsed.

New plan of action:

Take off all the injectors and have them professionally cleaned by Injectortune.

Replace the spark plugs (even though they were replaced last year)

Test compression with the kit which will be arriving this week.

I've been reading stuff about Lambda sensors and EGR valves etc and wondered if anyone could point me in the general direction when it comes to obvious stuff and general maintainence?

Edited 14 September, 201511 yr by Chefdave

First Welcome to the forum.

Most misfires on your engine are caused by the coil units, but your planned actions are the correct way to go, did they give you any fault codes?? as this might help to confirm what cylinder was at fault?

The lambda sensors wouldn't normally be a cause of misfires or the EGR

First Welcome to the forum.

Most misfires on your engine are caused by the coil units, but your planned actions are the correct way to go, did they give you any fault codes?? as this might help to confirm what cylinder was at fault?

The lambda sensors wouldn't normally be a cause of misfires or the EGR

Thank nige8021.

I've been scouring the web for info on this issue. Last night I even checked a couple of hundred pages of threads on here to see what I could dig up. Its like trying to find a needle in a haystack though!

Hopefully I can add to the knowledge as I work through this problem.

Yes they diagnosed a fault on cylinder 1. Shortly after I bought the car I purchased a £15 diagnostic tool too so I unwrapped it this week and confirmed to myself that the misfire is still on cylinder 1.

Last week I spoke to a local VW dealership and they quoted £85 for the first hour and £120 for any subsequent hours just to diagnose the problem. I thought 'sod that' and then bought myself the compression test kit for £20.

I've just had payment confirmation from Injectortune (for anyone else reading this he didn't respond to my emails so I just paid him through ebay to force the transaction through) so I'll be sending the injectors off Saturday, I'll be changing the spark plugs then too as I'm still waiting on my 3/8" socket extension bar. I've also chucked a bottle of injector cleaning fluid in the fuel tank for good measure.

Hopefully something will pay off. I just want to confirm that I'm not overlooking something obvious like excessive carbon build up in some of the components.

When you do the compression test, if there are any cylinders below 7bar, pour a small amount of engine oil down the sparkplug hole and then re-check the compression, if it improves the bore/piston rings are worn, if no change it's a valve leaking

Thanks. I did read something about this in my Haynes manual but now you've mentioned it I can't find it anywhere.

Either way low compression = an expensive fix? I still haven't got my head around bore/piston rings and valves yet. I just know that low PSI = not good.

My understanding is that the 3 cylinder models suffered from faulty valves pistons and bores more frequently. The 1 crumb of comfort I have is that I don't think its a common problem with my engine, but I guess I'll find out.

Edited 15 September, 201511 yr by Chefdave

Yes the 1.2L 3 pot has a known problem for eating the valves and the first indication is a recorded misfire !! the 4cyl engines don't seem to suffer the same but it's not unknown :(

If the low compression is a valve problem it's not as expensive to fix as a worn bore/piston rings, I've just had a cylinder head skimmed flat and a valve seat re-cut and that was £90

These engine seem to kill all there coils at the same time. My personal op roach to it is to get 4 yes it's a little expensive, BUT they will all be new. I would put in fresh plugs at the same time these engines are very funny about spark plugs. Sounds stupid but even though the could look fine changing it seems to make it run way better.

If you change them all, then keep the old ones as spare. Best place is around the spare tyre. You never know when they will come in handy.

Cleaning the injectors is ALWAYS a good thing I really can't recommend it enough. For such a simple procedure the results are amazing.

I would also recommend changing the fuel filter. It's under neath near the fuel tank. 2 clips holding the pipes on. Very easy job. These tend to look clean on the outside but inside will tell a very different story.

It seems in this country we have some of the most expensive fuel in the world but it's almost third world in terms of how dirty it is. You could even investigate and cut it open and look inside. A new one is white, I very much doubt yours is any other colour then solid black.

If your injectors are still on, then get a long screwdriver or similar and put one end onto the injectors metal body and the other end to your ear. You will hear a distinct clicking. This should be the same across all 4. The sound will no doubt change once they have been cleaned.

Thanks Dixy.

2 coils have already been replaced so far and I have 1 more in my toolbox so for the sake of £30 I could have a brand new set which will allow me to eliminate it from the list.

I will look into the fuel filter too, its something I hadn't considered before. I Just watched a Youtube video and it doesn't look too daunting. Also if I could replace it I'd be able to do most of the things commonly done during a service which I was charged £200 last year.

Its a good learning experience, but I still wish this misfire would **** off!

Wear good eye protection when changing the fuel filter. It can be under pressure and petrol in the eye is not fun.

Best of luck!

PoloD.

Injectors were sent off today and as Dixy advised I've decided to change all the coils and plugs

Compression test next. Any advice on this? Does the removal of the injectors have any bearing on the test? I've watched a couple of videos and some people take out fuses and things to stop any fuel getting through.

Thanks!

Edited 19 September, 201510 yr by Chefdave

Yep, remove the fuel pump fuse, and as it's a drive by wire throttle unit, get a helper to put their foot fully down on the accelerator pedal to open the butterfly as they crank it over, DO NOT be tempted to try and force the butterfly fully open or you'll be needing a new throttle body !!

Thanks once again nige8021. Hopefully I'll do this tomorrow (wet and dry tests if necessary) which will give me a clearer understanding of what is going on.

Had a similar issue on my BBY (same engine, just smaller inlet/injectors/TB) when I took the packs out to do a compression check, I didnt unplug them from the loom. Went to put it all back together and had a hell of a misfire.

Replaced 1 coil pack, improved it but still had a misfire so thought sack it and bought the remaining 3 (I'm on 107k so thought its worth the renewal) and its fixed the issue since.

I've just now put the refurbished injectors on, put on a brand new set of plugs and a new set of coils too. If anything the misfire was worse.

Two of the new coils didn't seem to seat properly so I put 2 old ones back and it idled a bit better but its still not perfect.

The report from Injectorune suggested the injectors were OK. I have the old plugs to examine, I need to find out why the 2 new coils weren't seating properly and I guess I'll do the compression test too, been avoiding it though.

This is very frustrating. I've been without a car for 3 months now.

Edited 24 September, 201510 yr by Chefdave

I don't know the answer - just an observation.

In your original post you mention temporary fixes - from Dec till June then a week then not long etc. My thought is this, that the 'fixes' by the garage had nothing to do with the parts they replaced but rather to do with clearing the ECU faults? And similarly your recent failure to achieve meaningful change in symptoms is because you have NOT been clearing the ECU.

When you clear the ECU it goes back to a default set of parameters and then 'learns' as you clock miles.

My only suggestion - you need VCDS (or similar) to properly clear the codes - an OBD device is not adequate. (Specifically I have an OBD/Bluetooth dongle that I run with the Android Torque App - it doesn't clear all the fault codes.) And the monitor every 50 miles what (new) codes appear to try start solving the root cause.

Thanks Dukla2000

If I have to buy it I was hoping I could get away with the $99 version as its not like I'll be doing this sort of work all the time.

But I just typed my VIN no. in and appears the cheapest one for me is $249.99 which is approx £165

Something to think about anyway. The garage want £40 to diagnose and clear fault codes, I'll only need to use it 4 or 5 times before I'm saving money.

Dunnoh about 9Ns but the free/shareware version is enough to clear my codes properly. (It is obvious as my LTFT gets reset to zero.)

(The thing with my OBD/Torque setup is it only shows/clears a code if the EML comes on. However if I clear codes and drive 20 miles VCDS will report codes, I guess effectively as 'warnings', even though nothing is as significant as needing a light on. And my OBD can't clear those but free/shareware VCDS can. But yeah, I am saving for the $99 version so I can do my throttle body adaptation and find out what else it can do. )

I've just refitted the coils and managed to get all 4 new ones on there. I was having trouble with 2 of them but with a bit of playing around managed to get them to seat down OK.

Fired it up for a few minutes and it idled at 1100, a bit jerky but probably OK to take out to the shops.

Next two avenues are the compression test (which I've been putting off) and VCDS.

Thanks for all the help so far, its saving me a fortune in mechanics fees!

Edited 26 September, 201510 yr by Chefdave

Update on the misfire problem

I took it to the garage for an ECU reset but it responded very badly and went into limp home mode. The mechanics as usual were helpful and competent and completely wiped their hands of the issue. However they did give me a 17961 code to work on which relates to air pressure and by making the problem worse they may have actually made it easier to find.

After a bit of digging around I pulled a cracked pipe from the back of the Throttle Body today, I'm hoping this is the cause of my problems.

Edited 3 October, 201510 yr by Chefdave

The cracked pipe I just removed

Is this responsible for 9 months of hell?

Edited 3 October, 201510 yr by Chefdave

Well found.

Does that go to the brake servo? I've no idea why VW use that plastic.

It will have been causing a vacuum leak, what the German's call Falschluft - wrong air.

My theory:

The modern bollocks of the ECU will then compensate by lengthening injector pulses and your sparkplugs will foul up with carbon, giving the misfire symptom - which vanishes when run on a smooth road or at the garage as no forces to flex the leaky pipe and ideal mixture will clean up the plugs of the carbon.

Edited 3 October, 201510 yr by dvderlm

Thanks.

Yes I think it runs into the brake servo, a rather large round thing on the driver's side.

The plugs certainly looked fouled up when I replaced them so maybe the ECU has been compensating for this lean condition with additional fuel.

I was on the verge of buying another car today, I even took it for a test drive this morning. I think I'll hold off until I replace this as I don't want to needlessly spend another £1000. This misfire has cost me £400 already in mechanics fees and parts.

Edited 3 October, 201510 yr by Chefdave

I forgot all abut those stupid pipes. Cracked on almost all 9n/3 I have seen

VW sell repair kits which are small lengths of rubber hose with 2 clamps

I have on a number of times just cut the plastic hose down and heated it and then shoved it over the outlet and then also used a strong jubilee clip.

I guess you could try that first before getting a new hose or repair kit? Wouldn't cost anything.

I had already bought the part so was too late for any cheaper work-arounds.

Just changed it and it still has a horrendous misfire.

Back to square one I guess.