Misfire cylinder 1, no luck changing coil/plug

[Xeratul]

Hello.
I have a problem with my A4 1.8T 2009. (130,000km).
It ran fine when I bought it but some days after I came home with 2000km more on the engine, it started getting small drops at RPM when engine was cold.
For example the car will shake on 1500rpm and rpm needle will drop up and back again 25/50rpm, barley see the needle moves.
Have tried swaped coil and plug with cylinder 2 with no luck so far. Can't see any leaks between intake and turbo.. (have ordered a leak finder just to get it checked)

The car runs fine(better) when all warmed up.
Reading with vagcom shows total 30,000 misfires on cylinder 1, and normal 1-500 on the other 3.
With engine cold I can easily see counter go up 10-20 misfires when driving 1km.

Only fault reading I have gotten is Engine running lean, misfire cylinder 1, random misfires. Does not turn on the CEL.

Advise on what things I can check will be very helpful :) at idle MAF shows 3-4 g/s.

Thanks!

[pearlwhite]

Did you try the spark plug ?

[Xeratul]

Yes tried both coil and spark plug.. read some where about carbon build up but I dont want to do 5hr work if its not helping😏

[bluefox280]

Since you have essentially eliminated the electrical components being the fault, now to look into mechanical.
As you search and found, you want to check the status of the amount (if any) carbon build up on the intake valves.

Second is to complete a compression / leak down test of the cylinders and compare between each.
If compression is bad, need to determine the source is its piston rings, bad seating valve(s) or other.

- Erik

[van462]

The MAF reading seems a bit high. I have the 2.0 vs 1.8 but doubt at idle the flow would be much different. Typical for me is 2.66 g/s warm idle 800 rpm, If you are in high idle 1100 to 1200 then those numbers would be close. you could try unplugging your MAF and start up. At idle the MAF isn't necessary, the computer will just use its baseline maps and tachometer for fueling vs the MAF reading (it won't rev well) but it does help point out if a MAF is sending a false signal to the computer. MAF is used more once you come off idle, as it uses the MAF plus boost pressure readings to validate air flow.
When cold the engine ignores the O2 sensor for mixture and uses mostly the MAF for fueling. Once warm the engine fine tunes the fuel trims based off of O2 readings.

[Xeratul]

Thanks for good ideas! I guess I must try to check the MAF and carbon buildup. Actually I have tried an aftermarket MAF from ebay (50$) but that just made car worse. Any tip for cheap and good maf? Also does my car have ICM, Ignition control module that I could try to check?

[Xeratul]

Today I notified suction at the little hole on the PCV, covered with my finger the engine started to shake. Is this normal or time to change PCV? http://i67.tinypic.com/zlitv.png

[bluefox280]

Any tip for cheap and good maf?

No; you will want an OEM MAF sensor - cheap knockoffs are not want you want.

Also does my car have ICM, Ignition control module that I could try to check?

No. You have coil-on-plug type ignition system.

- Erik

[Xeratul]

No; you will want an OEM MAF sensor - cheap knockoffs are not want you want.


No. You have coil-on-plug type ignition system.

- Erik

Nice to know! Any thoughs about that PCV? Worth a try?:)

[Xeratul]

Actually looks like a new PCV worked. No missfires so far! My secound audi in a row with this defective. Worth a change if anyone experience same problems :) Both 1.8T and 2.0T for me.

[Xeratul]

Looks like it came back after some days! But PCV seems fine now, I will post an update here when I have time to check it up. Still its no shakes when engine is at working temp. So come on ideas with things to check :)

[van462]

You could try unplgging the intake manifold to PCV hose and blocking off the manifold. You can use your thumb for a quick test. A piece of thicker plastic bag a zip tie works. You can even rev it some this way. If this solves the roughness then likely the block is leaking air in thru the front or rear main seal possible even the oil fill cap. When cold the ECU can't detect air fuel ratio problems well and doesn't correct for it. If this smoothes out your idle then likely its a air leak on the block. The newer PCV pulls a higher vacuum on the block. The block should be airtight and this limits the air going to the intake as just the blowby gases. If the block is leaking air in then more air than expected gets to the intake and throws off air fuel ratios.

[lettuce]

Faulty injectors are also a common problem with these cars. Since it seems to be cylinder-specific I'd lean towards that being the cause. Could be stuck shut, which would give you lean conditions and misfires. Of course vacuum leaks can do the same thing.

[audi@lifeB7]

Did you swap out your cam sensor


Sent from my iPhone using Audizine

[Xeratul]

Thanks for very good information. I have ordered a leak finde, the one type that you puts on intake after MAF and pressurise. I hope it can help find any easy leaks on hoses, and that its not the block leaking. Whats wierd is that when car is at working temp (90C) then almost zero misfires. But when cold I can easy get 100 misfire on Cylinder 1 in only 2-3KM drive. Any chance its the N80, N75 or N249? Since the PCV was sucking air, what more is in the line of breaking becouse this malfunction?

Havent tried changing cam sensor, is this an easy DIY?

And with injectors you mean fuel injector? Can be worth a try, but also would this sort out when car is warm?

Last time I drove a testdrive with vagcom I got about 200misfires on cylinder1, and 2misfires on cylinder 4. zero error messages.

[Xeratul]

Update, still noticed some shaking/rpm up/down when cold...

[Quattro420]

It seems you have spent a lot of unnecessary money trying to fix your car, drive your car cold till it miss fires (engine light flashing) or shows in vag com. Pull over and remove spark plug for cylinder 1 and 2 (the cylinder closes to the radiator is 1 and 2 is beside it ) use a small light look in the spark plug hole if cylinder 1 is wet looking compared to cylinder 2 you have a leaking injector. Call the closes Audi dealership give them you vin and ask if you have a warranty extensions on the injector, if you do you will get a free injector labour and all but there gonna try and charge you to do a carbon clean since you save the 3 hrs labour for r&r the intake but you would pay the 2hr time for carbon clean, not a bad deal at all or you could just do the free stuff the injector but it makes the most sense to just pay them the 2 hrs and let them do the dirty scrubbing.

[Xeratul]

Thanks I will have a look at that, not used so much mone on parts yet, the PCV was Faulty.. I noticed this areal is "wet" https://goo.gl/photos/eN5iqH98fZyc5moW9 can it be a gasket or is it normal?

[Xeratul]

You could try unplgging the intake manifold to PCV hose and blocking off the manifold. You can use your thumb for a quick test. A piece of thicker plastic bag a zip tie works. You can even rev it some this way. If this solves the roughness then likely the block is leaking air in thru the front or rear main seal possible even the oil fill cap. When cold the ECU can't detect air fuel ratio problems well and doesn't correct for it. If this smoothes out your idle then likely its a air leak on the block. The newer PCV pulls a higher vacuum on the block. The block should be airtight and this limits the air going to the intake as just the blowby gases. If the block is leaking air in then more air than expected gets to the intake and throws off air fuel ratios.

Tried this and when unplugged the engine started running very bad, with the thumb blocking the hole it was ok but still not stable, so back to normal idle when plugged hose back on, so guess I can eliminate this leak?

[van462]

Yep, it's just a quick test to eliminate a few of the high failure components. The other usual suspect in the engine misses when cold vs warm is carbon buildup on the intake valves.

[Xeratul]

It seems you have spent a lot of unnecessary money trying to fix your car, drive your car cold till it miss fires (engine light flashing) or shows in vag com. Pull over and remove spark plug for cylinder 1 and 2 (the cylinder closes to the radiator is 1 and 2 is beside it ) use a small light look in the spark plug hole if cylinder 1 is wet looking compared to cylinder 2 you have a leaking injector. Call the closes Audi dealership give them you vin and ask if you have a warranty extensions on the injector, if you do you will get a free injector labour and all but there gonna try and charge you to do a carbon clean since you save the 3 hrs labour for r&r the intake but you would pay the 2hr time for carbon clean, not a bad deal at all or you could just do the free stuff the injector but it makes the most sense to just pay them the 2 hrs and let them do the dirty scrubbing.

Hi, I cant see much difference down there, exept that nr 1 and 4 are more black and 3 and 2 is more clean..