Check Engine Light / Misfires / Start Stop Errors at Random

If it is the fuel, I will name and shame the station to help others on this forum - but I don't want to discredit a station yet until I know for sure. Again I will update the thread as I go through the diagnosis to hopefully help others.

I will get my battery checked next month just in case its caused by weak power from the battery before the alternator has a chance to fully kick in? Although car started fine in sub - zero temperatures. Using a simple multimeter test suggests the battery is good but I'll get it checked at halfords using their CCA devices. If the battery is weak, Ill probably do the big battery mod as mentioned in your other thread.

That fuel filter doesn't sound fun to replace given that I work on my car in public side streets! - Hopefully its not that, as the car doesnt hesitate when pulling hard on to slip roads... well as hard as the 1.2 can do XD.

afropelican said:

[FONT=&quot]OBD ELEVEN doesn’t provide much additional info for this symptom - has been great for coding though!
[/FONT]

Click to expand...

It will also allow you to dump out live data so you can look at things like adaptation values for individual fuel injectors or timing retard for each cylinder to see if there is anything out of balance on that cylinder.


...if it creaks, it's probably made by VAG

By that statement I meant it doesnt flag up any VW specific fault codes other than those generic misfire codes flagged up by my basic scan tool. (Although it did tell me my fuel cap doesnt lock and my key fob battery is low, so I'll need to get that looked into).

Looking at the misfire counter on live data - by the time I've hooked up the scanner and loaded up the app following a check engine light, given that the misfiring stops in well under 30 seconds - the live misfire counter doesnt increase. Even left the counter running for a 25minute drive following one of the instances of misfire. This confirms my evaluation that the misfires stop shortly after startup.


The total number of misfires for the lifetime of the vehicle is quite high - but I think thats normal for these engines given what I've read in other threads. I only purchased the vehicle in January, at over 50k miles.
Total Misfires Cyl1 - 14721
Total Misfires Cyl2 - 15338
Total Misfires Cyl3 - 22824
Total Misfires Cyl4 - 18776


I've taken a few screenshots of the other live data following a misfire on startup but am unable to interpret it. Some of the data that may be of use is:
Knock Sensor Voltage Cyl1 - 2.505 V
Knock Sensor Voltage Cyl2 - 2.432 V
Knock Sensor Voltage Cyl3 - 3.691 V
Knock Sensor Voltage Cyl4 -2.695 V
Leakage Air - 0.7kg/h
No. of Manual Engine Starts - 10161
No. of Automatic Engine Starts - 11471

Cylinder 3 might be of concern - given the increased misfires / higher knock sensor voltage? Or it could just be bad fuel? The timing retardation for cylinder 3 is 0.0 degrees.

coil packs are on the way out??...swap no3 to the no 2 (the lowest V) & record again...

This is a bit weird. Not sure why the knock sensor voltage would differ at all. You do obviously have a problem on cylinder three, but the business of it misfiring only during startup to me suggests problems with the injector or fuel pressure even? It's much easier to swap the coil pack however so give that a go first.


...if it creaks, it's probably made by VAG

I appreciate the help, will continue to keep the thread updated.


Heres hoping its not something so serious as fuel injector / supply problems. I will go back to my old fuel once the tank is nearer empty so I can eliminate that as a variable.


What are your thoughts on injector cleaners? Since owning the car its had a double dose of redex and a bottle of wynns put through the tank. Should I run another bottle of redex through it?


Got a long road trip due soon, so I've ordered a spare coilpack to keep in the boot just incase - might be a simple question but from which end is cylinder 1?
Ill be switching coilpacks 1 with 2 and coilpacks 3 with 4 for now as the misfire code has not been on cylinder 1 or cylinder 4 yet so its not critical to know now. But knowing which side is cylinder 1 willl help if I need to replace the coil pack! I will be swapping the coilpacks when my vw connector removal tool arrives as I had a hard time attempting to remove it by hand. I will also inspect all the connectors for any corrosion.


The misfire on startup is so random and brief that it doesnt even store as an intermittent code in OBDELEVEN let alone as a permanent code in the generic scan tools.

Fwiw It's entirely up to the ECU what becomes a permanent code, nothing to do with the type of reader you use. OBDeleven gets the exact same data out of the engine that the official VW workshop diagnostics do.

I thought cylinder 1 was always opposite to gearbox end? Could be wrong.

I dont think there's a lot of evidence that injector cleaner does much at all, except on ancient cars where they would have been run with genuinely crap fuel for their first ten years. Most decent fuels have some cleaning compounds in them anyway. That said, it's a cheap thing to do and I don't think it will harm anything either.


...if it creaks, it's probably made by VAG

I agree - can't prove the additives effects either way. It was either using the additive, doing nothing or trying that water decarbonisation method from BMAC VAGS. His method could be viable, but I'm not comfortable spraying water through my intake! Can't justify cost of the carbon clean services.

Yeah I'm aware that the OBDELEVEN will pick up on the more advanced codes - given that it can't pick up a code (except when immediately following a misfire on startup - is why there's no point in taking it to the mainstream car dealer I bought it from). I phoned to discuss their diagnosis procedure, and based on that its likely they'll just deny the fault exists as it wont show up on their scan tools and I won't even be able to replicate it for them to show the issue.

The intermittent and short duration of the fault is such that even the ECU doesnt think its worth storing as a code!!

Update:
Replaced Coilpack 3.
Swapped Coilpacks 1 and 2.
Changed Engine OIl to 5w30 Castrol Edge and used a Mann Filter.
Cleaned contacts on all coilpack connections using electrical contact cleaner.
Ran redex through the tank when I had the suspected 'bad' fuel in.
Now, I'm back to using shell at my old fuel station, and am now on the second full tank.


After all this: the misfire cameback this afternoon exhibiting the same symptoms, Random multiple misfire for less than 30 seconds on start up cylinder 2 and 3 misifre. With the knock sensor being slightly higher on cylinder 3 than the other cylinders.

This problem is really getting on my nerves, as the symptoms can reappear after days making it unclear whether what I am doing is having any effect or not!
Any suggestions or help is appreciated.

Update:
Got battery tested, I have an exide 59Ah 320A (DIN)640A (SAE). Was told the battery is good (although unsure as his machine measured at 514CCA).
I've ordered another 3 Coils so the whole set can be changed to see if that makes a difference.

What are peoples thoughts on carbon build up could that be the issue?
I have ran a couple tanks with various fuel cleaners in the system it is my understanding that since its direct injected they can't clean the valves so I've ordered Seafoam spray.

Also incase its useful, 99% of the time the car has been doing short 10-25mins city driving at low revs (e.g. 30mph in 4th gear).

Update:
Replaced all coilpacks.
Also flushed coolant and changed gear oil - irelevant to problem but included for completeness.

Symptom appears to still exist.

Any suggestions for next steps?

Certainly something's not happy. Do you have any remaining errors or warnings in the ECU?

Have you had any opportunity to put in a decent length run at higher speed or at least using more throttle to blast some air through the cylinders?

...if it creaks, it's probably made by VAG

Nothing stored on the ECU as per OBD Eleven.
Not really been on decent runs / use a lot of throttle when driving this car.

A typical day consists of anywhere between 2 and 6 journeys, 2-4 miles in length. Almost always short stop start city commutes. Very rarely has it been on the motorway since I bought it. The longest run its been on is 20 miles on the motorway when I picked the car up. Also, generally, given this is not particularly a fast car, I don't tend to rev it a lot, with me often changing up a gear even before its indicated in the mfd for fuel economy purposes instead.

For now I will try to drive using some more throttle and slightly more enthusiastically to get more air through the cylinders.

When I get the chance, my current next approach is, based on my research and advice given in this thread:
1. Use seafoam spray (as CRC valve cleaner is expensive in the UK) to try to get some carbon / gunk off the valves if there is any.
2. Add some sort of fuel cleaner to the tank again - going to use Comma this time given my previous experience with their brake and transmission fluids.
3. Follow your suggestion on taking it on a decent run at higher speed,
adding to this I will do the run following the seafoam treatment with fuel cleaner in the tank and will incorporate a >3000RPM for 20mins cycle into the run as touched on in the VW patent.

I suspect it is carbon / gunk buildup causing this other problem, unless there are other routes to follow that may cause this?

Update: 22nd May 18

I've completed the steps in the last post.
Fingers crossed.

24th May:

Same symptoms: sufficient enough this time to trigger the check engine light again. Any suggestions for next steps?

Thinking about hard resetting the car by unplugging the battery for 30 mins and touching the leads (disconnected from batteries together as per humblemechanic)- would I need radio codes etc? What sort of settings will I lose?