# Misfire cylinder 3 and 4



## mckinnan (Jul 19, 2017)

Hi I have a misfire on cylinder 3 and 4 on my 2012 Jetta 2.5 se.

I have come to the point where I have no idea what is causing my problem. *I did a reset of my code every time I tried something new with my scanner*

I have changed all spark plugs - Misfire didn't changed
Found some oil in my sparkplugs well and VW changed my valve cover gasket on warranty - Misfire didn't changed but I have no more oil in the wells
Changed all coils packs - Misfire didn't changed
Verified capping on my sparkplug - Gapping is ok
Tried switching the coil pack and sparkplugs - Misfire didn't move
Changed fuel filter and added an injector cleaner - the check engine (misfire) disappeared for about 2 months and is now back

I've pulled out my injectors cleaned them and there was dirt or something like it on my 3 and 4 injectors not the other ones. I then tried switching it from its cylinder but again the misfire didn't moved.

I then go to a VW specialist garage and he does a compression test, he check sparkplugs, coil packs, wiring and a bunch more other tests. After hours of searching a problem he is clueless too, as he says all his test are perfect and my motor runs great. So he's thinking its an electronic problem since my check engine only come on when I start the car in the morning when there's humidity. If I do a reset my check engine won't come on until I start it the next morning, he then goes into protection mode as the mechanic says. 

When I drive, I can hear it doing misfires from time to time, so I think there's a real misfire occurring. But I have no idea what it is. He goes for the control module and I think it's on the fuel side since the injector cleaner did make my car go without misfires for 2 months.

*important* My misfire problem popped up 3 weeks after I started to gas at an other service station. I came back to the gas station I used to gas and with a new filter and an injector cleaner the misfire disappeared. It reappeared when I was in vacation and I did gas to an other station. But I also tried an injector cleaner again but this time it didn't worked.

I gas at a Shell gas station

Sorry for the long text, if anyone know what the problem is or have seen it before please tell me what to do, it would be greatly appreciated.


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## Jamesmk5 (Aug 21, 2015)

Tighten your intake manifold bolts. Sometimes they come loose


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## mckinnan (Jul 19, 2017)

They were indeed loose. I wasn't able to tighten the last bolt as my hex key wasn't long enough. 
I bought a new set and should get it soon.
My check engine is still coming back on, maybe it's because of that last bolt?


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## afawal2014 (Jul 13, 2016)

Just to confirm, have you tried to switch the fuel injector from cylinder 3 or 4 to a cylinder that is NOT misfiring?


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## mckinnan (Jul 19, 2017)

Yes I tried moving my injectors but the misfire didn't move..


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## MLue1 (Apr 27, 2008)

I would suggest taking this further, removing the intake manifold clean the sealing surfaces and replacing the intake manifold gaskets and having the intake torqued down properly.

Make sure you know which cylinders are #3 and #4, on this engine number #1 cylinder is on the drivers side of the car, number #5 cylinder is on the side where the accessory belts are located.


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## afawal2014 (Jul 13, 2016)

If you've got a scan tool that shows you live data, you can look at fuel trims to see if the air fuel mixture is too lean. That would point you more towards the intake manifold gasket.

Here's a few other things to look at:

1- Take a quick look at your wiring to the injectors and coils. Make sure there's no signs of damage or corrosion.
2- Check the wiring on the main harness. Make sure the connector is well seated, no pins out of place, etc....


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## mckinnan (Jul 19, 2017)

All the wirings seem fine, i didn't changed the gasket just yet but ive tighten that last bolt and nothing have changed. Could it be the n80 valve? As the problem occurs only on a cold start?


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## afawal2014 (Jul 13, 2016)

mckinnan said:


> All the wirings seem fine, i didn't changed the gasket just yet but ive tighten that last bolt and nothing have changed. Could it be the n80 valve? As the problem occurs only on a cold start?


Everything I've read about the N80 valve issues is problems starting up the car, or longer than normal cranking. Are you having difficulties starting the car in the morning?
I haven't come across cases of misfires due to a bad N80 valve. I recently changed my N80 valve because it was getting noisy and I could hear it ticking during idle - there was no driveability issues, just more of a nuisance.

Misfires are typically caused by either fueling or spark issues. Everything you've listed seems to have ruled either one out:
- new plugs
- new coils
- injector cleaner & switching to see if the CEL follows the injector.
- fuel filter, etc.....

At this point, to me you have 1 of 2 issues:
- Bad head gasket - but you said the VW shop did a compression test and all was good. Just for a sanity check, is your coolant level decreasing? Any white smoke from your exhaust at all?
- Electrical issue - wiring may look ok from the outside. You may need to do a little deeper dive an check continuity using a meter of the injector plugs and coil plugs for Cylinder 3 & 4.

Have you had your ECU read by a VAG-COM? Sometimes stored faults are not accessible to a generic reader if they are not throwing a CEL.


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## mckinnan (Jul 19, 2017)

yup the mechanic did read with a VAGCOM and deleted all the stored codes but this didn't worked too. I just changed the n80 as it was cheap but it did nothing. Now that you tell it, when I start the car it as no problem starting but i hear a ticking noise until the rpm get down. No white smoke from my exhaust nor coolant leaking too. I'll need to go to a shop for them to test the wirings. This is starting to drive me crazy as im still paying that car its a 2012 but no more on warranty..


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## afawal2014 (Jul 13, 2016)

mckinnan said:


> yup the mechanic did read with a VAGCOM and deleted all the stored codes but this didn't worked too. I just changed the n80 as it was cheap but it did nothing. Now that you tell it, when I start the car it as no problem starting but i hear a ticking noise until the rpm get down. No white smoke from my exhaust nor coolant leaking too. I'll need to go to a shop for them to test the wirings. This is starting to drive me crazy as im still paying that car its a 2012 but no more on warranty..


The start-up ticking noise is normal you're describing. Just all the moving parts in the engine on cold start up.

What were the stored codes? Did you get a list?


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## mckinnan (Jul 19, 2017)

He did not give the reading with the vagcom but my reader shows only misfire on cylinder 3 and 4 and randoms misfires. As i had a lot of deposit on my injectors 3 and 4 and that the injector cleaner made my car go without misfire for about 2 months could it be just carbon build up?


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## afawal2014 (Jul 13, 2016)

mckinnan said:


> He did not give the reading with the vagcom but my reader shows only misfire on cylinder 3 and 4 and randoms misfires. As i had a lot of deposit on my injectors 3 and 4 and that the injector cleaner made my car go without misfire for about 2 months could it be just carbon build up?


Carbon buildup is not typical in these engines - as long as you're on top of your oil changes and using good quality gas. One of the previous posts suggested you replace your intake manifold gasket. This may not be a bad idea because it will also allow you to take a look at the how clean or dirty your valves are. If the valves have a lot of carbon build up, then this will cause the misfires.

How's your fuel economy?


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## mckinnan (Jul 19, 2017)

Guess ill go look for a new intake manifold gasket and yes my economy as decreased. Ill keep you updated.


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## Ronny Bensys (Apr 17, 2014)

I would suggest replacing intake manifold gaskets and injector sealings, all inner and outer.

Take a photo of your old spark plugs and post here. Picture of the newer ones would be best.


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## mckinnan (Jul 19, 2017)

Ronny Bensys said:


> I would suggest replacing intake manifold gaskets and injector sealings, all inner and outer.
> 
> Take a photo of your old spark plugs and post here. Picture of the newer ones would be best.


My mechanic tells me this isn't an intake manifold gasket, that i do not have the symptoms + i've used a propane with a tube while the car is running to see if idle would increase because of an air leak and found nothing. Wouldn't changing the injectors from cylinders change the misfire from a cylinder to another one?


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## Ronny Bensys (Apr 17, 2014)

mckinnan said:


> Wouldn't changing the injectors from cylinders change the misfire from a cylinder to another one?


Yes, it would, provided the injectors are bad. I suggested to replace all sealings to drop any likelihood of air leakage before digging further into cylinders and valves.

I'm surprized mechanic did a leakage test but he didn't inspect spark plugs. Spark plugs are best indicators for diagnosing misfire issues. Any oil leak into the cylinders will leave clear signs of unburnt residue on them.

You should inspect your both old and newer spark plugs. You'll not have to spend money to check them. Check the color, condition and contamination. Find your old plugs, take a photo and post to the forum. You should also remove and inspect your newer plugs. Remove all of them and compare misfiring cylinders with healthy ones.


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## mckinnan (Jul 19, 2017)

Yes the mechanic did checked the spark plugs, gapping and all. I'm now going to an other mechanic. And we have eliminated that it isn't spark plugs, coil pack, injectors, vacuum leak (didn't check brake booster), spark plug wires, pcv valve, n80 and other stuff.

He thinks it is something that as to do with temperature since my check engine flashes only on a cold start, hes rooting for coolant temperature sensor.

I also need to mention that I used to have a catback on my car and also that i hear poping noise in my exhaust not only startup but also when driving. My brake pedal was also very hard to push one day this winter when the weather was -35 c.

What's really concerning me is that I used to always gas at the same gas station and when i switched were i put gas i got those misfire. I tought it was bad gas. Changed fuel filter and ran a fuel injector cleaner and the misfires were gone for 2 months. Seem to have came back when I had put gas at another station instead of the one i usually go to.

Im thinking something fuel related or a valve that is stuck open or closed, maybe O2 sensor or EVAP system related? I have no other code than random misfires and misfire on cylinder 3 and 4. So maybe something that could malfunction without throwing a code? I just tried putting an injector cleaner back in and it did nothing.


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## racerpoet (Apr 20, 2013)

So what did you find?


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## mckinnan (Jul 19, 2017)

So if anyone come across this problem, I finally found the answer. I had water in my gas tank. Since water isn't compressable the water wasn't able to escape the injector causing misfires. I added a product to my gas that mixes with the water and make it able to get pass the injector ex : ethanol 99%, or stuff at any autoshop. I ran it for 3 weeks with it and now everything runs fine, no more misfires. You could also drop down the tank and empty it, i just found my solution easier since its winter right now.


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## racerpoet (Apr 20, 2013)

mckinnan said:


> So if anyone come across this problem, I finally found the answer. I had water in my gas tank. Since water isn't compressable the water wasn't able to escape the injector causing misfires. I added a product to my gas that mixes with the water and make it able to get pass the injector ex : ethanol 99%, or stuff at any autoshop. I ran it for 3 weeks with it and now everything runs fine, no more misfires. You could also drop down the tank and empty it, i just found my solution easier since its winter right now.


Glad you figured it out! :thumbup:

Any idea how you got water in your tank though?


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## mckinnan (Jul 19, 2017)

I was putting gas at a shell station near where I live every week since about a month. 2 weeks after i got my misfire problem, the gas station close for renovation of gas pumps and tank. The mechanic from the same area as me, told me I wasn't the first one who came to him with this problem and that was putting gas there too. I could find you the exact product ive been told to use if you want to.


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## racerpoet (Apr 20, 2013)

That'd be cool. I haven't had any issue like that, but good to know for the future I guess. haha


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## Ljoh049 (Sep 6, 2021)

mckinnan said:


> So if anyone come across this problem, I finally found the answer. I had water in my gas tank. Since water isn't compressable the water wasn't able to escape the injector causing misfires. I added a product to my gas that mixes with the water and make it able to get pass the injector ex : ethanol 99%, or stuff at any autoshop. I ran it for 3 weeks with it and now everything runs fine, no more misfires. You could also drop down the tank and empty it, i just found my solution easier since its winter right now.


I know this post is really old but I just wanted to say this saved my ass this weekend. My 2013 gti was throwing these exact symptoms. 
I changed the plugs, coil packs, pvc valve, and had the fuel system fogged and had the throttle body and injectors checked. Then had some water absorbing tank cleaner put it. FINALLY the coding stopped and we’re at some semblance of normal again . Ty so much.


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## kcampbe (Jul 15, 2014)

Any brand name recommendations?

Sent from my SM-G986U using Tapatalk


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## KL51212 (Aug 29, 2021)

Pretty well all of the gas tank water (or moisture) eliminators use isopropanol (often called IPA, or IsoPropyl Alcohol, on the label).


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## roubaixGLI (Dec 5, 2019)

This seems to have worked for me on my misfire problems too.


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