FSI erratic/uneven running

Lasse H

Member
I'm confused by how my FSI runs. Issues:
1) Idle is not as smooth. Revs drop around 50RPM, every few seconds or so. The engine also sounds a bit like a diesel, but I assume this is a feature. :)
2) With relatively low revs (1200-2000) and big gear (4/5) especially engine pull becomes sometimes noticeably uneven. It feels like slight misfire. On some days it works perfectly.
3) Sometimes it feels like torque on low revs (until 2500 or so) is a bit less than normal. Maybe I only imagine it, or not.

I have found several reports about very similar sounding FSI symptoms, but not seen any solutions.
I'm starting to worry if the FSI is actually "supposed" to run like this...? Or can it actually have smooth steady idle, etc. like normal cars? :confused:

-These issues are relatively minor. I wouldn't expect most drivers paying enough attention to notice.
-Grounding near headlamp has been cleaned. No effect, except no error codes after this (at least for a few days.. I'll check again soon). Before there was some random misfire reported.
-Spark plugs are new, air filter new, EGR is nearly new.
-Cylinder head was recently removed, cleaned and checked.
-Several intake air leaks were fixed during last repair shop visit (oil filler front pipe, oil filler cap on valve cover, some broken pipe on between engine and firewall) -- no effect to these issues.
-Cold/warm engine does not make a difference.
-I am not anymore sure if the engine has behaved this since I bought the car (4 years ago or so), or did it start in some point later.

Any ideas what to test with VCDS, or otherwise?
One option could be to replace all ignition coils, but that gets a bit expensive just to be on the safe side. If there was one or a couple slightly faulty ignition coils I'd assume ECU being able to detect which one...?
 
Hi Laase H
I have recently bought an FSI and it has exactly the same problem.
i did have an error code for the exhaust temp sensor which i replaced todayand cleared the code, but still has uneven revs.
When i press the throttle to and position and hold it there the revs go up then down by about a quarter. so if i hold the revs at 2000 they drop to 1500.
I am thinking there must be a leak on the vacuum side of things, a perished hose or gasket somewhere.
I will be doing some investigating in the near future (6th April) when I have some time off.
I will post any results I find at the time, but if anyone has any suggestions or can point me in the direction of a vacuum schematic I would be very grateful.
Harry
2004 1.6 FSI
 
Hi Harry,

I read anything about the FSI as I have same. Welcome to A2OC.

Sending a private message that may be of some use.

Andy
 
Any useful info in the PM? I've got similar issues. I bit the bullet and replaced all coil packs, might be a bit smoother but didn't fix the revs on idle. I'm thinking it might be an injector on its way out. That's a bit too much of a bullet to bite though..

Thanks,

Chris


Sent from my iPhone using Tapatalk
 
Welcome Nordic neighbor,

No error codes?

I removed and cleaned the Air Flow Meter and the Trottle Valve with LIQUI MOLY Injection Cleaner and got back the smooth idle.

"Several intake air leaks were fixed". Have you checked the Crank Case Ventilation hose, hidden under the Intake manifold? No crack in the EGR Pipe?


 
Hi, i have not had a chance to properly look at the car yet. I did remove check and clean the main earth behind the passenger headlight and that seemed to make a small difference. I definitely have a leak issue as i can smell petrol under the bonnet, no leaks anywhere so must be vapour from somewhere. I will be having a proper look and posting results from Thursday onwards. Thanks
 
Hi, and thanks for replies! Perhaps even just 'FSI misfire' could be busy enough topic to have its own forum... :)

The FSI was not running too well yesterday and today, and now I had chance to check error codes. Intermittent misfire was present in three cylinders. Also the code for random/multiple misfire detected was present. :( Now 'intermittent misfire' has been reported for every cylinder during a period of a couple weeks.

Hmm. Intake air leak codes have not been present since fixes at garage. This air leak error code seems to appear quite reliably, so I would find it likely the EGR pipe and the Crank case ventilation hose are OK. Is the ventilation hose accessible or visible somehow? I have never checked it. The EGR pipe I checked a couple years ago (after intake air leak error) but I didn't notice anything unusual. But if I remember right it has a protective mesh, so fully checking it isn't really possible. The reason for air leak then turned out to be the front oil filler pipe (that fix eventually failed and was properly fixed recently).

I have once cleaned the airflow meter. It took a while to realize it made no difference. The throttle body has been cleaned at a garage a couple years ago. Despite all dirty FSI intake horror stories, they told me it wasn't especially dirty! Same thing with the head during most recent repair shop and machine shop visit: they told it wasn't significantly dirty!! Of course it was completely cleaned anyway. (The car has done about 180000km.) The only complaint was that the spark plugs were rather black, even though they were just a couple year old (Bosch plugs if I recall right).

New air flow sensor? 4 new ignitions coils? Some other sensors to suspect or check?
Misfire in all four cylinders does not especially sound like a failing injector, and feels unlikely all 4 would be failing in a rather similar manner..?

I wish good luck to Harryn! That petrol smell does not sound good, especially with FSI. That is definitely not a symptom with my car, I've never noticed it. Could it be a leaking fuel line? A loose spark plug?! Or something wrong with fuel vapor handling system (I've no idea how it is implemented on this BAD)...
 
Things are proceeding... But not to better. Today engine warning light lit up, three times. Misfire error codes are not intermittent anymore, although I do not notice any clear difference.
16684 - Random/Multiple Cylinder Misfire Detected
16685 - Cylinder 1: Misfire Detected
16687 - Cylinder 3: Misfire Detected

I tried to find fuel trim values from ECU to get some clue about injectors' condition, but couldn't find these.

As a cheap test, I decided to try using Liqui Moly injection cleaner, but I'm not especially optimistic about it.

If things get worse this quickly, it seems like I'll have to make a repair shop appointment rather soon.
 
Have you tried to swap the coilpacks to see if the fault follows the move?
Have you checked the wiring feeding the coil packs?
 
Have you tried to swap the coilpacks to see if the fault follows the move?
Have you checked the wiring feeding the coil packs?

Thanks for ideas!

As I was not sure about condition of any coil packs, I bought one new Bosch coil and changed it to cylinder 3 because it has easy access and has had error code present often.
I did a test drive of about 20km diverse driving. Car felt working reasonably well, but issue was still clearly present. My greatest wish was that misfire had disappeared from cyl 3. Back at home I read codes. Nothing!?! I started engine again to listen if idle was really that good. It was not. Engine error light started blinking almost instantly. I attached laptop again. Same codes as in my previous message were back.

I am not sure about wiring. I don't see any significant damage here, but it has been protected with wrapping and tubing practically all way. Unless here is some typical fault I wouldn't like to start cutting this open.
 
The car is now in shop which did engine work earlier. I'm not especially optimistic about their troubleshooting skills, but we'll see. At least they should be able to do some other work (not related to this issue).

I found misfire counters yesterday (groups 015 and 016). They looked weird. Cylinder 1 and 3 misfire counters were increasing quickly and on rather even pace. Cylinder 2 misfire was increasing occasionally.
During this engine idle sounded relatively good to me, which made me suspect if only cylinder 2 misfires were genuine misfires and 1&3 misfires just some kind ECU diagnostic failures.
 
Hi Guys,
Had another look at the car today, mainly looking into petrol smell. Managed to get snake behind intake manifold and there is an electrical sensor that looks shiny and wet. (Video below) Looks like i will need to remove the inlet manifold to check out the problem :mad:
[video=youtube_share;mTWbFM4frjU]https://youtu.be/mTWbFM4frjU[/video]
I also checked the spark plugs and all are quite sooty, but on the plus side that means they are all working :eek:. no wet ones. The wiring is quite hard and I will be changing it at some point.
Spark 1.jpgSpark 2.jpgSpark 3.jpgSpark 4.jpg
Looks like its had a new fuel pump (or do they all look like below) and at least one sensor, previous owner must have had problems.
Sensor.jpgPump.jpg
To sum up so far...
Problems are - Irratic idle - when i press and hold accelerator the revs rise and then fall by about 10%.
Car drives fine at speeds and no error codes.
Not been put on VAG yet, may get the chance tomorrow.

Findings - Plugs sooty but working (not sooty in the tip)
Fuel leak (behind inlet manifold i believe)
Replaced faulty exhaust temp sensor
Throttle body looks spotless inside

Next steps - Put car on VAG for more info
Strip inlet manifold to deal with leak (fingers crossed its just a gasket)
 
I have similar issues but not had time to investigate. Will be checking at the weekend. Look forward to your next update.
 
If you fix the Intake manifold I would recommend that you also replace the Fuel Pressure sensor (high pressure) and the Intake_manifold_flap_air_flow_control_valve (what a name) when you have the intake removed.


Intake manifold control valve-schematics.JPG
 
The intake manifold isn't too bad to remove, you'll need an upper intake manifold gasket and you'll need to disconnect the left hand engine mount and tilt the engine forward to get the manifold off once all the fasteners have been removed.

Nick
 
Nice to see progress here. :)

My car visited yesterday our "regular" local repair shop, but guys there admitted being not able to troubleshoot it, and told a car electronics specialist will be needed. (Another problem was found though: just a bit over 2 years old Bilstein B6 rear shock was broken!)

The first diagnostics shop I contacted mentioned things like pressure testing the intake system, measuring fuel pressure, inspecting MAF and possibly also checking camshaft timing. Last one was interesting and unexpected point, as the engine was disassembled recently.
 
Nice to see progress here. :)

My car visited yesterday our "regular" local repair shop, but guys there admitted being not able to troubleshoot it, and told a car electronics specialist will be needed. (Another problem was found though: just a bit over 2 years old Bilstein B6 rear shock was broken!)

The first diagnostics shop I contacted mentioned things like pressure testing the intake system, measuring fuel pressure, inspecting MAF and possibly also checking camshaft timing. Last one was interesting and unexpected point, as the engine was disassembled recently.

I recently tried the camshaft timing - Did not make a difference.

I sometimes (once every couple of months) get a fault code for inlet camshaft over advanced - which is what made me check. There is a basic settings test you can do to test the inlet camshaft timing control system, though I can't remember it off the top of my head.

Fuel pressure is carefully monitored and controlled by the ECM, any faults here are normally flagged up as a fault code. Air leaks are a good place to look but anything significant will agian throw a fault code!!!

I'm going to strip the inlet manifold, remove injectors and send for ultrasonic cleaning and flow testing - When I do I will post results, i'm really hopeing this put an end to my FSI's behaviour!
 
Thanks to Steaman and Topsie for the sound advice.
I got the car on Vagcom today and NO error codes, I was actually hoping for something to give me a clue.
Ah well, next is to get gaskets and sensors ready for intake strip down which will be in a weeks time as I have that whole week off.
 
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