Hi all, 

 

With everything going on and currently being furloughed, I thought I would get round to a few issues that have been bothering me for a while now. 

 

Car details: 12 plate 1Z3 CDAB engine: 1.8tsi 152.

 

One of the main issues I'm experiencing i an extremely rough initial idle (bounces between 300 and 1100rpm erratically). This seems to be at its worst after the car has been left for a few hours. After the initial start up if I leave it for 20 mins or so, when I start it up again it is still rough but no where near as bad. During the idle it also seems like the engine has no idea how much air it should be taking in. 

 

I currently have a Ramair intake in place of the standard airbox, which definitely seems to make the issue worse. However the issue definitely persists even with the standard airbox in place. It is less noisey, but similar changes to rpm regardless. 

 

There is also:

- oil around the oil filler cap

- no smoke from anywhere

- excessive oil consumption (around 2. 5 liters in top ups in 12 months and 10k miles)

- a slight, but noticeable stutter throughout the rpm range (particularly around 3500 and more noticeable when decelerating)

 

The car recently had a misfire on cylinder 1 which was remedied with a coil pack change, this cleared the code and the issue resolved. However when fault finding I found that the plug on cylinder 1 seemed blackened compared to cylinder 2, almost as if it was running rich. There was no oil or fuel in the cylinder that I could see and the plug was not wet, just blackened.

 

Also when it had this fault it was scanned at the garage and they said there was a mild intermittent MAF issue, but not really something they could or would look at fixing. 

 

Power seems fine, although I have had this issue for a while so if power is down I might not necessarily know. However no flat spots. 

 

I thought this might be a PCV Valve issue, however removing the oil cap when the engine running, there was no resistance at all (what I've been told is if there is a lot of pressure behind it then that could point to the pcv). Whilst it's only around £55 to replace, I don't want to do that if not necessary. 

 

I have checked (looked at) vacuum pipes as best I can but honestly I don't know where I should be looking. 

 

I've tried to include as much information as possible, but any questions just ask. And thanks in advance! 

 

Cheers, 

 

Josh

 

unplug the maf and see if it settles the idle. bouncy idle means the ECU is getting either bad/wrong airflow or fuel rate readings.

if it's the maf and you unplug it it defaults to a value and works out the fueling to that default. idle should settle.

if it's a fuelling issue, it could be an injector.

Per @mac11irl have you tried unplugging the MAF and see if the idle returns to normal?

 

There is a good fault finding video for the pcv on humble mechanic.  You can check the small hole in the side of the PCV/ Fine Oil separator by putting a finger over the hole. There are other tests as there are more than one mode of failure for the PCV.

 

The idle should change when you pull the dip stick.  There should be vacuum from the PC ventilation system.  It can be measured with a small scale gauge.  

 

There are two different current revisions of the PCV and when I replaced about 18 months ago, it was £65 or £70 plus vat!  Don't try unproven pattern part on this.

 

2.5l/ 10k miles or 16k Kms is not too bad, you probably already know the reputation these engines have.  If there are no oil leaks it is most likely the dreaded  ring problem.

 

Try a good 5W40 vw 502.00 oil if you are not already using it. It may lower consumption from 5W30 long life.  Has the vehicle been on a long life service schedule - that tends to exacerbate the scraper ring deficiencies.

 

There was a chap on here who had a vRS EA888 2.0 TSI, based on same engine platform as yours, he had a hesitation that he could not get rid off no matter what he tried.  He got so annoyed he sold it and bought a BMW!  I suggested a number of things but it never got sorted on these forums!  For the ease of it, and eliminating a weak point, I would possibly change the other 3 coil packs out as well.

On 25/04/2020 at 20:40, mac11irl said:

unplug the maf and see if it settles the idle. bouncy idle means the ECU is getting either bad/wrong airflow or fuel rate readings.

if it's the maf and you unplug it it defaults to a value and works out the fueling to that default. idle should settle.

if it's a fuelling issue, it could be an injector.

Hi Mac, 

 

Thanks for that. 

 

I have just tried unplugging the MAF just after starting the car cold and it seemed to fix the issue of the car not knowing how much air to take in. I will try starting it tomorrow without the MAF plugged in at all to get a more conclusive answer.

 

If it isn't having this issue with the MAF unplugged is that more likely that the MAF needs cleaning/replacing or something else? 

 

Thanks In advance

1 hour ago, TheClient said:

Per @mac11irl have you tried unplugging the MAF and see if the idle returns to normal?

 

There is a good fault finding video for the pcv on humble mechanic.  You can check the small hole in the side of the PCV/ Fine Oil separator by putting a finger over the hole. There are other tests as there are more than one mode of failure for the PCV.

 

The idle should change when you pull the dip stick.  There should be vacuum from the PC ventilation system.  It can be measured with a small scale gauge.  

 

There are two different current revisions of the PCV and when I replaced about 18 months ago, it was £65 or £70 plus vat!  Don't try unproven pattern part on this.

 

2.5l/ 10k miles or 16k Kms is not too bad, you probably already know the reputation these engines have.  If there are no oil leaks it is most likely the dreaded  ring problem.

 

Try a good 5W40 vw 502.00 oil if you are not already using it. It may lower consumption from 5W30 long life.  Has the vehicle been on a long life service schedule - that tends to exacerbate the scraper ring deficiencies.

 

There was a chap on here who had a vRS EA888 2.0 TSI, based on same engine platform as yours, he had a hesitation that he could not get rid off no matter what he tried.  He got so annoyed he sold it and bought a BMW!  I suggested a number of things but it never got sorted on these forums!  For the ease of it, and eliminating a weak point, I would possibly change the other 3 coil packs out as well.

 

Thanks for that! 

 

I have tried a few things, including putting a finger over the small side hole, but I couldn't notice any noticeable difference truth be told... I will try a few of the other diagnosis tricks. Including taking it off and checking the valve on the base and the diaphragm inside. 

 

The advice to unplug the MAF seems like it might have worked, but I will be double checking tomorrow to see. 

 

Just to be clear, This may have solved the issue of erratic air intake on startup, however when the car settles to it idle rpm there is definitely some stuttering/unevenness in the idle. There are no codes showing in a read, so I think I might have the plugs out tomorrow to check the gapping on them and likely replace the rest of the coil packs whilst I'm at it. 

 

In terms of oil consumption, I can't see any leaks anywhere. Nothing on the ground, nothing in the engine bay, apart from around the oil filler cap as mentioned before. I have been topping up with the quantum platinum 5w40, but it was serviced at a local garage and I believe they have used 5w30. The car is serviced every 12 months with fresh oil and has been since new according to the log book. I've been contemplating having the oil done on a more regular basis now that it's getting on a bit! 

 

I'm hoping I don't have to resort to buying a BMW! Although the N57 325D has been on my radar for a few months now... 

 

Thanks again for the input, much appreciated! 

no problem. 

if it is the maf, the idle should just fully settle down. 

leave it unplugged, bring it for a little drive around to warm up. stop a few times and see how the idle behaves.

if your lucky it's just a knackered maf.

dont buy a pattern part, get a genuine one... buy cheap buy twice really applies to sensors on VAGs.