# Help! Cylinder 4 Misfire Fault Codes P0300 & P0304



## C00P5TT5 (Jul 10, 2016)

Please can I have some suggestions on what might be the problem.

I have a misfire 4 code, as shown below. I have changed the number 4 coil pack and all 4 spark plugs but am still getting a misfire. I also swap the 1 and 2 coil packs and still get a misfire on cylinder 4. The engine light flashes but doesn't stay on.

Any ideas anyone?

P0300 - Random/Multiple Cylinder Misfire Detected Upper limit exceeded
static
Priority: 2
Frequency counter: 1
Driving cycle: 255
Mileage: 86393 km
Date: 2019-12-23 10:34:45

P0304 - Cyl.4 Misfire Detected Upper limit exceeded
static
Priority: 2
Frequency counter: 1
Driving cycle: 255
Mileage: 86393 km


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## Hoggy (May 8, 2002)

Hi, Have you checked if the plug is actually sparking, as could be the supply to the coil.
Next check would be the injector.
This should help.
http://wiki.ross-tech.com/wiki/index.ph ... 304/000772
Hoggy.


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## Dec11 (Sep 27, 2016)

Join the club :roll:

I've replace coils and plugs but no joy yet, I'm replacing the PCV when it arrives in the post. Will be looking at injectors and ignition wiring next if that doesn't cure it. I'll let you know if my PCV clears it.

It's a pain to isolate!


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## C00P5TT5 (Jul 10, 2016)

Just changed the evap purge valve as a code for that came up but didn't return after being cleared.. But no change still misfiring on cylinder 4.

Now I have to get it recovered as I guess its not OK to drive?


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## Hoggy (May 8, 2002)

C00P5TT5 said:


> Just changed the evap purge valve as a code for that came up but didn't return after being cleared.. But no change still misfiring on cylinder 4.
> 
> Now I have to get it recovered as I guess its not OK to drive?


Hi, If you do have to drive, don't let it idle, keep revs above 1K rpm otherwise lots of stress.& remove No 4 injector electrical connection. Have you checked that injector connection?
Hoggy.


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## C00P5TT5 (Jul 10, 2016)

How do i go about checking the injector connection?


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## Hoggy (May 8, 2002)

C00P5TT5 said:


> How do i go about checking the injector connection?


Hi, Remove the plug from injector. Resistance at room temp across the 2 horizontal connectors should be 12-13 Ohms.
Make sure the plug/socket connection is clean secure.
Hoggy.


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## C00P5TT5 (Jul 10, 2016)

Would a failure in the pcv cause a misfire on one cylinder?

Reason I ask is that I done a 5 hour drive recently and my engine cover has no insulation left in it so that amount of heat could melt the rubber.... I replaced the pcv 4 years ago?


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## Hoggy (May 8, 2002)

Hi, Very unlikely.
Hoggy.


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## Barr_end (Oct 19, 2016)

Everyone who has tried the obvious..

Boost leaks
Vac leaks
Coils
Plugs

It's time for injectors.
Known poor filter baskets on the TFSI injectors.

Get yourself to somewhere that can test them properly.

Injector clinic within R-tech performance will be able to sort it, also get your inlet carbon cleaned with walnut blasting whilst you're there.

Running the engine round with poorly injectors can cause serious damage! Don't!


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## Wolvez (Jun 22, 2018)

Try cleaning the ground wire under the vacuum pump. That's the main ground supplying the coil wiring harness.


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## C00P5TT5 (Jul 10, 2016)

Before I bite the bullet and pay for recovery and costs can someone advise on the following:

1. Would a turbo gauge leak cause a misfire on one cylinder being number 4

2. Would a failed or dirty maf sensor also cause the same issue (I have a ram air filter)

Or, as I suspect, is it going to be the injector on the basis that no other cylinder is misfiring?

Ta


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## Dec11 (Sep 27, 2016)

PCV made no diff to mine, typical! So it's onto injectors for me also.

Anyone know of any guides to pulling injectors? Search on here seems very limited?


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## C00P5TT5 (Jul 10, 2016)

This might help, good luck. I'll be sending mine off to a indie as I am limited to a road side work area.






Keep us updated on how you get on.


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## Dec11 (Sep 27, 2016)

C00P5TT5 said:


> This might help, good luck. I'll be sending mine off to a indie as I am limited to a road side work area.
> 
> 
> 
> ...


Yeah, saw that one, but looks too different from our front wheel TT's, could be easier or more difficult to that A5 Quattro.


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## C00P5TT5 (Jul 10, 2016)

Update.
I have a faulty fuel injector.

But the nightmare continues, the indie that has diagnosed the fault can't get it on the two post lift to fix it because of the side skirts 

This morning I struggled with the recovery guy to get it on the truck because of the maxton splitter on the front.... After sourcing some scaffold boards, it was on.

Maxton splitter and skirts look good but are a pain in the arse.


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## C00P5TT5 (Jul 10, 2016)

Anyone know roughly how much it will cost to fix a fuel injector?


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## Dec11 (Sep 27, 2016)

C00P5TT5 said:


> Anyone know roughly how much it will cost to fix a fuel injector?


Injectors are 180 - 200 for Bosche or Audi, lots of cheaper injectors on ebay but don't know how good they'd be.

When I got quoted that price I thought the lad meant for 4, but no, for 1!!


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## Barr_end (Oct 19, 2016)

C00P5TT5 said:


> Anyone know roughly how much it will cost to fix a fuel injector?


Ring R-tech performance. 
There was a deal for inlet & injector clean at £325, so you'd be able to assume that it would be £200 or less for injectors at a guess.

You post *ALL* the injectors to them.

They'll be flow tested, any that can be saved will be, any that fall below the limit, in the pre clean/rebuild test, you'll be advised to buy new.
But the reason you do this, if you do indeed need a/some new injectors...
They ALL get taken apart, cleaned, the shit paper filters that cause the injector failures are binned off, new metal mesh baskets are put in place. 
The fault will never happen again.
Once rebuilt they are flow tested again to ensure they are correct.

You may only be suffering misfire codes on one cylinder but that doesn't mean all 4 injectors are flowing at the correct rate.
Just means that one is bad and is easily measured.

I won't go into massive detail, but think the magic number of flow was 66, as low as 50 is enough to kill the engine with lack of fuel. With my car that showed 0 signs driving or with codes it was missing, mine were still something like 62, 64, 56, 59.
These were all saved, rebuilt, flowed at 66 and have been mint for the 2 years they've been done.


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## C00P5TT5 (Jul 10, 2016)

Got the call from the garage earlier today and although I have not seen the invoice the work for a single fuel injector, oil and filter change and rear discs and pads (which I supplied) is £1,207.00.

The garage did not estimate, quote or call me before hand so its a bit of a shock.

Is this unreasonable, or sound about right?


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## Hoggy (May 8, 2002)

Hi, Appears to be rather excessive. How many hours labour?
Hoggy.


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## C00P5TT5 (Jul 10, 2016)

Not sure haven't picked it up yet and not been "walked through" the invoice


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## Barr_end (Oct 19, 2016)

Sounds f****** mental to me! Personally.
That being said, it would be interesting to see what they break that down to for investigation/diagnosis costs though.

Inlet is not a nice job granted, but think the book time doesn't exceed 4? hours for removal and refit.

As you may not of seen in the reply I posted above Rtech charge £325 (on sale) to remove the inlet and injectors, walnut blast the inlet valves in the head, clean the inlet out, flow test, rebuild, clean and reflow test ALL the injectors, new seals on them and refit the lot (Obviously supply at cost new injectors if they are deemed past saving).

New genuine injectors can be sourced at around £100-120, for example.... Awesome GTI not known to be cheap, or massively over priced:
https://www.awesomegti.com/shop-by-car/ ... gKGpPD_BwE

Plus new seals for the other 3 injectors as the inlet has been removed

Hate to bang on but this work carried out on your car, has not future proofed the car (as much as is possible) and you could now still suffer same issue on other injectors, or even eventually on the fresh one that's been fitted.
Don't use any extra fuel additives as much as possible, these are a very likely cause to accelerated the degrading of the paper/plastic filter baskets inside the injectors.


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## C00P5TT5 (Jul 10, 2016)

The saga continues. The invoice shows plugs and coil pack, which I told them I had replaced already, the plugs had done zero miles.... And after handing over £1,207 the car made it half way off the forecourt and the engine light started flashing!

Went back into the office and said do you want to run a scan. Yes he said, it will only take 2 minutes. Yeah I know that, so why is it a £48 charge?

Anyway, misfire on cylinder 1 now... Which the invoice shows was identified but not fixed?.... Madness.

Also the guy who ran the odb asked if it had been mapped, because the owner said it flys.... Took it out for a run yesterday apparently...... So that's why I am a quarter of a tank down


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## C00P5TT5 (Jul 10, 2016)

If I'm reading the invoice correctly they have removed the faulty number 4 injector and put it in number 1 cylinder???

Why would you do that knowing that, and I told them that, the no4 injector is failing!

The worst bit is that they did not estimate or call me before doing any of this... If they had I would have said replace all 4 if 2 are gone.

My local garage said because I have paid then its a "bring back" and I won't have to pay any further labour costs?


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## C00P5TT5 (Jul 10, 2016)

What I would like to know is it worth me telling them to replace all 3 injectors, assuming that the issue with cylinder 1.

Or will they say that a new job and charge another grand?

Rtech is too far away from me with the car in its current state unfortunately


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## ab54666 (Nov 18, 2019)

7 hours to replace spark plugs WTF!


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## C00P5TT5 (Jul 10, 2016)

Nah, he's rounded the Labour into one line


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## C00P5TT5 (Jul 10, 2016)

Although he replaced the 4 spark plugs that had on been in the car for a matter of hours!


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## ab54666 (Nov 18, 2019)

Seems an odd way to work.

Also says all 4 spark plugs heavily carbonated - how can that be if you replaced them hours before? Something doesn't smell right. Sounds like they've no idea so just keep swapping parts out.

I'd send the injectors off, i've used these guys before; http://www.injectortune.co.uk/index.html but other options available such s it seems R-Tech.


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## Barr_end (Oct 19, 2016)

After the replies and the invoice, I wouldn't let them touch the car again!

From what I can read, they took the worst injector and put it back in the car! The f*** would you do that for!
Also not like they were trying to keep the bill cheap and were telling you as they went along!
You're saying you'd literally just replaced the plugs and they are blagging that they were carbonated?

Also don't see the injector seals listed in the parts total, to me if it's not on there, they haven't replaced them which is a proper mistake.

Do you have decent breakdown cover?
If you do, could easily consider using this to get a flatbed ride to R-tech OR if you can find another Fuel injector clinic that happy to do the labour.
Maybe this repair is maybe beyond this garages knowledge? Especially on this engine? Then they've muddled through? Then charged you alot of money


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## ab54666 (Nov 18, 2019)

I agree I probably wouldn't go back, but always difficult when you've thrown that amount of money at a garage to pretty much no avail, you want them to sort it.

Anyone else local, VAG Autoworks?


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## Dec11 (Sep 27, 2016)

They've well and truly stroked you there mate. They did work you didn't even ask for and never quoted you, you'd no contract with them in that case.

For start off I did my front discs in 45mins and did plugs and coils within 30mins, and I had never worked on one of these before!

I'd be off to the small claims court with that one!


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## Taylortony (Feb 10, 2012)

Using your registration even Audi charge less for diagnosis. £60

https://www.audi.co.uk/account/fixed-pr ... ceCode=GEN

£345 at audi to replace the rear pads and discs and that includes the parts!

https://www.audi.co.uk/account/fixed-pr ... Code=BPDRE

Charged you twice for Sundries.

Also says all 4 spark plugs heavily carbonated

I would have asked for them, also they are simple to clean. In fact I would want all the parts removed So you can see they have been done!, easy enough to say plugs etc but clean and refit them.


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## C00P5TT5 (Jul 10, 2016)

Update:

The guy phoned me at 10:45 to say they had worked on it this morning (opens at 8 ) and the injector on cylinder 1 has been replaced.... So as a good will gesture he would only charge for the parts and not the labour.... I told him that's good as I never intended to pay any labour cost. And I want both of the old injectors back.

Picked the car up and he said that he swapped injector 4 (the f***** one) and put it in cylinder 1 as it wasn't missing that much.... F****** idiot.... I think because they only ordered 1 injector, he thought it would get it off the forecourt.

Anyway £186 later and I have the car back. He said he didn't have time to road test it (nah cuz you done all the fuel on the last test) so with the 3 miles I have done the cel has not come on.

I have the old injectors which I will try and get refurbished incase the other two go.

I also have a brand new set of plugs and two coil packs in a bag in the boot as spares... Ffs


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## MarksBlackTT (Nov 29, 2016)

So, without sounding too harsh, you keep droning on about how 'your' garage is stitching you up left, right and centre and yet so many people on here are trying to advise you on the best way forward, you still keep giving a negative response as to what you are actually going to do about it to rectify the problem and doing absolutely nothing positive. You keep giving a 'garage' copious amounts of money, and your petrol, and they are laughing at you!! Get a grip and stop them taking the absolute p**** out of you. SERIOUSLY.


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## Taylortony (Feb 10, 2012)

Id be chatting to trading standards, does your breakdown cover include legal? They might help, btw with the AA you can insure against certain faults for about £5 a month and covers up to £500 of the bill several claims a year.


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## TheGr8Unknown (Jun 2, 2021)

Any updates on this post ? Just had same error pop up on mine...


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## C00P5TT5 (Jul 10, 2016)

Misfire was due to a failed fuel injector....do the usual checks....i.e. swapping coil packs to see if the misfire moves...if it doesn't, change the spark plugs...if it still is missing, chances are it's the injector


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## TheGr8Unknown (Jun 2, 2021)

Thanks for reply,
Swapped number 4 and 3 coil packs and now showing misfire on number 3 cylinder... looks like coil pack failed


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> Thanks for reply,
> Swapped number 4 and 3 coil packs and now showing misfire on number 3 cylinder... looks like coil pack failed


Did you get this sorted mate, what TT you got


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## TheGr8Unknown (Jun 2, 2021)

Yeh thanks m8, and a blue 1


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## TheGr8Unknown (Jun 2, 2021)

: D


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> Yeh thanks m8, and a blue 1


Any pics, I like a blue TT


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## TheGr8Unknown (Jun 2, 2021)




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## TheGr8Unknown (Jun 2, 2021)

Ok, (balls out as the auzzys say) I have a 8n, I posted my 1st post in haste and didn't realise I was on the 8j part, but all the advice was still very helpful and I managed to sort my problem out. 
So all in all 2 good lessons learnt at once 

And here's my blue TT


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> Ok, (balls out as the auzzys say) I have a 8n, I posted my 1st post in haste and didn't realise I was on the 8j part, but all the advice was still very helpful and I managed to sort my problem out.
> So all in all 2 good lessons learnt at once
> 
> And here's my blue TT


I like that looks good, seems familiar - is that you Reg from West Midlands

Easy mistake to make at your age Reg


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## TheGr8Unknown (Jun 2, 2021)

It is Shane! u kno me Dow ya me man ...10 points to sum 1 who guesses what part of the Midlands  (pmsl)


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## TheGr8Unknown (Jun 2, 2021)

Ur not allowed to guess Shane


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> It is Shane! u kno me Dow ya me man ...10 points to sum 1 who guesses what part of the Midlands  (pmsl)


Yeah it's me mucka, go by many names these days - some newer than others tho 8)

Needs a bit of symmetry those rear lights


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## TheGr8Unknown (Jun 2, 2021)

Needs other things doing 1st tho


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> Needs other things doing 1st tho


You still got that mate who sprayed his car British Gas Blue cuz he liked the vans that much :mrgreen:


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## TheGr8Unknown (Jun 2, 2021)

Ur so naughty (pmsl!!)


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> Ur so naughty (pmsl!!)


Van spotter now ay he, not allowed at the train station anymore after the incident arguing with the staff about the paint colour on the old British Railway yellow carriages


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> It is Shane! u kno me Dow ya me man ...10 points to sum 1 who guesses what part of the Midlands  (pmsl)


You got the 150 in the end then  you still cutting hair?


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## TheGr8Unknown (Jun 2, 2021)

I'd probably make more money cutting hair and work less hours !
Although I cud do ur hair this sat if u want


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## Pow3rL3ss (Dec 15, 2008)

TheGr8Unknown said:


> I'd probably make more money cutting hair and work less hours !
> Although I cud do ur hair this sat if u want


You still doing back, sack and crack as well


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## chil4actor1 (Jun 26, 2019)

C00P5TT5 said:


> Just changed the evap purge valve as a code for that came up but didn't return after being cleared.. But no change still misfiring on cylinder 4.
> 
> Now I have to get it recovered as I guess its not OK to drive?


Hi just a suggestion however have you tried cleaning the injectors, throttle body housing and maf sensor? Also assuming you still have the standard air box like me replace the filter, I have a stage 1 remap and I get better throttle response with the standard air filter than I did with a panel k&n, for the throttle body clean job, if it’s never been done like mine it’ll have a green gasket, buy some instant gasket before you do the job, trust me it’s amazing stuff and very resilient, I’ve even used it to seal air leaks not water leaks and once set job done, you will also need carburettor cleaner for the maf sensor clean job and it seems obvious however check the air ways for the intake isn’t blocked by debris or leaves....


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## chil4actor1 (Jun 26, 2019)

chil4actor1 said:


> Hi just a suggestion however have you tried cleaning the injectors, throttle body housing and maf sensor? Also assuming you still have the standard air box like me replace the filter, I have a stage 1 remap and I get better throttle response with the standard air filter than I did with a panel k&n, for the throttle body clean job, if it’s never been done like mine it’ll have a green gasket, buy some instant gasket before you do the job, trust me it’s amazing stuff and very resilient, I’ve even used it to seal air leaks not water leaks and once set job done, you will also need carburettor cleaner for the maf sensor clean job and it seems obvious however check the air ways for the intake isn’t blocked by debris or leaves....


Based on what you’ve done so far I would deduce it’s clogged injectors...


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## wsantos (Sep 7, 2020)

chil4actor1 said:


> Based on what you’ve done so far I would deduce it’s clogged injectors...


I was struggling with a cylinder 1 misfire up to a month ago, replaced the sparks and coil pack but it didn't work. Had an engine carbon detox done which included throttle body/intake system clean (similar process shown in the video below), HHO and fuel system clean. It cured the cold start rough idling AND the misfire. Car drives so much smoother now. People don't usually think that carbon build up could cause these issues. 

Stage 1, FWD, 2008, 70K miles, petrol. 

Link to video 




Sent from my SM-G996B using Tapatalk


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## Rufflesj (Jun 22, 2020)

Additives do not work on direct injection engines, not that they're much better on any other engine in the first place


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## TT'sRevenge (Feb 28, 2021)

Rufflesj said:


> Additives do not work on direct injection engines, not that they're much better on any other engine in the first place


They don't put it in the tank though in the video, he actually sprays it in the intake instead of adding it to the tank.

Problem there is this would not work well (the way he's doing it) on a turbo car since the spray would have to travel through the turbo, through the charge piping, through the intercooler. Not much (if any), would deposit on the valves.

You'd have to spray it in near/after the throttle body--could actually use the PCV connection on the intake manifold--disconnect there and spray in, but you'd also have to block it off enough to not create a massive vacuum leak either. Basically have to do the old sports needle, hose, and rubber stopper method, or similar.

It seems like if you do it right, it will have some efficacy, probably better than most other products, but certainly not a total cleaning solution.


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## Rufflesj (Jun 22, 2020)

TT'sRevenge said:


> They don't put it in the tank though in the video, he actually sprays it in the intake instead of adding it to the tank.
> 
> Problem there is this would not work well (the way he's doing it) on a turbo car since the spray would have to travel through the turbo, through the charge piping, through the intercooler. Not much (if any), would deposit on the valves.
> 
> ...


Thought it was a another 'in the tank' snake oil


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## C00P5TT5 (Jul 10, 2016)

Fyi before my missfire happened, which was due to a failing injector, i had a terraclean procedure done... probably about a year before.... I only had it done as a preventive measure and because I do a lot of short trips and read so much about carbon build up.

After the terraclean I didn't notice any difference.....and it didn't seem to prevent the injector issue that I feared would happen in the future.

So for me the only true way to deal with it is to walnut blast it.

What i also done was to send two of the injectors that were replaced off to be refurbished...one came back as good as new, the other was said to be not repairable (for which I was not charged anything, other than the postage cost)

I think by design the oem injectors are not great and the refurbishment did use different gauze to the originals


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## TT'sRevenge (Feb 28, 2021)

Rufflesj said:


> Thought it was a another 'in the tank' snake oil


It is, if you use it the way it's intended/directed. The "off-label" use of sucking it into the intake seems to have _some_ degree of efficacy, just not a whole lot. Might be useful for periodic cleaning after a full cleaning (or from when the car is new) to mitigate the amount of build up over time.


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