More FSI Misfires

Philip

Member
Trying to track down the cause of misfire codes on an FSI - problem arose on starting, the car had been parked for a couple of hours after a brisk 40 mile motorway journey. Engine light was flashing at idle and the following codes weres stored:

16684 - Random/Multiple Cylinder Misfire Detected;
16685 - Cylinder 1: Misfire Detected; and
16687 - Cylinder 3: Misfire Detected.

The flashing check engine light goes out when driving and returns when sitting at idle - there is a very slight but noticeable roughness to the idle, just evident in the rev counter needle. Occasionally it will illuminate constantly, but only briefly.

Plugs are about 5k miles old and are all in good condition and the same good colour; I've swapped all plugs and coilpacks, but the fault codes stay with cylinders 1 and 3.

The only problem I've found is a tiny pinhole in the corrugated EGR pipe, which looks like it has been caused by the wiring bracket attached to the side of the head rubbing on it - I covered this with a blob of superglue as a temporary test, but it hasn't made any difference.

I've also cleaned the main earth on the chassis rail and the one on the cylinder head (both were already clean and didn't really need doing) and gone through all the visible ignition connectors with contact cleaner. I also reset the throttle body with VCDS, just to see if it made any difference (it didn't); inlet and throttle body both look very clean. It's had two or three cans of Normfest fuel system cleaner through it over the past year and the fuel filter is also about 5k miles old. It has always been run on Super Unleaded in my ownership (V-Power whererever possible) and has done about 104k.

Any other suggestions before a compression test and pulling the injectors?
 
Check the wiring harness from the coils, they can get brittle and fracture (recently checked mine, though mine were okay)

I've exhausted pretty much every avenue other than injectors, which is now on my list - my MOT tomorrow may take it to the top of my list though!!!
 
Check that the hole has not reappeared or there is crack in that egr pipe. Otherwise I'm going with injectors sorry
 
Me either, however, in my head if the insulation was breaking down and causing shorts, it would not just be at idle, but right through the range. My misfires are at their worst between idle and 3k, after that it's fine. I'm convinced it's injectors, I just hope ultrasonic cleaning and flow testing is enough, don't fancy buying new!
 
Is it logical that the injectors works fine at high rpm but not below 3k?
Have you checked the Crankcase Ventilation Hose?
 
To me, yes.

At lower RPM and engine load the injectors operate at a lower pressure. If the injectors are coked up on the nozzle or gummed/blocked up internally, the lower pressure will exacerbate a poor spray pattern or the gummed/blocked injector will not allow sufficient flow for effective combustion.

An air leak (via CCV) will lead to incorrect fuel trims and (eventually) throw a fault code, or at least be easily identifiable through VCDS.

Well, that's my take on it at least.
 
Sounds plausible, but it's strange that the same error occures on two injectors at the same time.
 
Other than being a common fuel rail, i'm struggling to bottom this one out to. My misfires are cylinder 2 & 3 at idle and only cylinder 3 at 3000rpm...
 
Errors relating to the common fuel rail emanate from insufficient high (fuel) pressure and. The high fuel pressure can be meassured with VCDS and evident att high rpm and hign load.
The error should also be the same for all cylinders.
 
An error that I haven't had (yet!!)

Has anyone looked at the state of their inlet valves? I'm aware that the FSI engines can suffer from carbon build up as their is no fuel to "wash" the valves in the induced air. When I remove my injectors i'm going to have a good look and see what 153000 miles looks like...
 
I have just swapped injectors and my inlet valves was ok. I cleaned the intake manifold and checked the intake manifold flaps. My main problem with my Fsi, is lack of power and hesitation at acceleration or heavy load. I think it is due to a to lean fuel to air ratio.
 
Of course - 01 Engine - Readiness

There's a bunch of different 'self tests' the car continually carries out. Mine never seems to complete any other than Air Conditioning and Catalyst Heating.
 
Any updates related to this? I'm feeling like I'm having a nearly identical situation here, just I'm getting misfires in three cylinders (1, 3, 2).

But considering ignition order (1-3-4-2) it sounds possible that the problem you are/were having is only in the cylinder 1. ECU could detect false misfires to the next cylinder (3) occasionally. That detection is not bullet proof AFAIK. Checking misfire counters (value groups 015 and 016 if I remember correct) could reveal something. For my car misfires seem to happen simultaneously to all three cylinders (but never to 4) BUT nearly always cylinder 1 counter "leads" clearly...
 
Not yet, there are a number of people experiencing near identical issues. I really hope I or somebody manages to work it out, I'm also hoping it's a single component that's causing issues for everybody, but doubtfull.

Mine seems to be cylinder 3, though cylinder 2 decided to have a misfire also for a few days, which then magically dissapered. Strange...
 
Update - misfire apparently gone, no further sign of the check engine light. Chucked a can of Normfest OT100 into a quarter-full tank - not a great believer in fuel system cleaners and the like, but it was either related to that or it resolved itself.
 
Go on then, who's gona go next lol?

I've thought about terraclean or hydrogen cleaning of the engine, keeping in mind they don't go through your injectors... I've also read audi recommend not to use any fuel additives with the BAD engine, but if it works i'm game!
 
Back
Top