Sluggish Cold Starts

[f00glee]

@Dave J - I did have that code a about a year ago. It meant that my radio didn't turn off instantly soon as the key was pulled from the ignition. When I had my RNS315 fitted by eddieNL he replaced the ignition switch for me which solved it. Otherwise no issue starting and the radio would eventually turn off when the car properly shut down after half an hour, but still wasn't right. Part seemed a bit of a pain to change. Is at the complete opposite side to where you put the key in, looks like a translucent white disc if you take the cover behind the steering wheel off.

Some bits and bobs to do first this morning. But I'll then have another go with the car now that's it's sat overnight. I'm too lazy to pull the fuse so I'm just going to climb in the passenger seat. If pressures all look good but it struggles, then perhaps the carboned up head is a point for consideration (have seen it mentioned in conversation elsewhere).


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[f00glee]

Sure enough the start up was a bit spluttery this morning. Id give it a 5 out of 10 for "splutteryness". 

Heres some numbers (spluttery, today):

 bar    bar    %
6.28   7   5.9
6.28   7   5.9
6.29   7   5.9
5.99   7   5.9
5.46   21.28   27.5
4.73   35.61   27.5
3.96   60.86   35.7
3.82   57.05   46.7
3.98   52.22   46.7
3.97   51.19   45.5
3.93   51.03   47.5
3.9   50.16   51.8
3.98   50.23   56.5
4.17   49.44   56.5
4.45   49.46   50.6
4.61   49.44   46.3

This is over roughly 3 seconds, the car took perhaps the middle 1.5 secs to fire up, the rest is pre and post startup. After this all pressures stabilised. col 1 = low side pressure, col 2 = rail pressure, col 3 = lpfp duty cycle.

The low side pressure does dip a little as the engine is cranked (from 6.2 down to 3.9 before coming back to 4.61 once started) after this, then idling all the number stay stable at these values. Comparing to yesterdays good start, the low side pressure started at 6.83 and never dipped to then come back up again

Not spluttery, yesterday:
 bar    bar    %
6.83   7   5.9
6.83   7   5.9
6.96   7   27.1
6.73   18.84   26.7
6.26   31.84   27.1
5.57   51.77   27.5
4.75   62.84   34.9
4.37   53.66   36.1
4.36   52.51   37.6

So there is a bit of difference, but would this really be enough to make it splutter? The rail pressures climb equally quickly on both logs and I'm sure that's more important than the low side pressure. Plus the low side pressure down to 3.9 bar in the spluttery start up log hardly indicates the lpfp being starved. The minor differences in number are probably the difference between sitting for 2 hours and being a bit warm, and then sitting over night and being stone cold. Sample rates from each log are slightly different as i was logging 1 extra block yesterday.

So assuming my fuel pressure sensors arent lying, fueling seems to be okay? Leaving spark and air... the plugs are, from memory, only a few years and ~12k old, coils never changed so by all rights spark should be okay (but I do plan to change plugs and coils next service anyway). As for the air supply - this bring my thoughts back to carbonised intake ports.

Between plugs, coils and intake cleaning were looking at £500. Not money I want to spend all at once just chasing this minor issue, but will be done as part of routine maintenance over the next year or so. So barring any other suggestions ill just come back here to post if any single piece of maintenance makes any difference.

[pudding]

So it starts within 1.5 seconds?  That is totally normal.  You might get a cough or two before it settles to a smooth idle, but it's all normal.   Cranking for ages and then running on 2 or 3 cylinders for 5 or 6 seconds before settling down is considered abnormal.

[slix]

Yeah mine sometimes does this when it's a cold start. It's done it for the 2 years I've had the car. I just learnt to get round it by cycling the ignition on twice before cranking the engine. This seemed to help.

[maxamplitude10]

I'm on 106k and have a similar diagnoses doesn't sound crisp when turning over and firing. I found that by turning on the ignition and pressing accelerator once before firing it started fine?
Any input from anyone on this?

TX
Dean

[pudding]

Could be signs of a dirty throttle body.   Perhaps try running it through the calibration cycle in VCDS - Engine module, basic settings, block 060.

[maxamplitude10]

Thanks Pudding I'll hook it up later and run it through:-)

[markrtw]

This is strangely all great reading. Thought I am going mad with my ED30 not seeming to start the same way a few times in the morning. When cold at home (on a slanted drive) it either splutters to life, or starts keenly. Does it too at work on a flat surface...

Mine was perky as you like for a while on turning over after fitting the highly rated Varta by Bonelorry's thread (https://www.tayna.co.uk/E44-Varta-Silver-Dynamic-Car-Battery-P7726.html). Better cranking power, and no issues for ages.

As per f00glee's post, (apart from the battery) mine has had the following new parts as improvements in the time I have owned it,

Loba HPFP
New R8 coils
New VW LPFP
New sensor on HPFP

At my next (looming service) I want the fuel filter replaced for the newer 6.6bar version anyway as part of good practice (never been changed).

Mine is on 86k now (bought on 47k in 2012, and always run on VPower in my ownership). Could this simply be down to a carboned up head? I know the injectors can get a bit tired, but mine doesn't show any issues when running in terms of missing, etc...

I have Vagcom, but am no master when it comes to logging stuff...

I do have an intermittent ignition switch fault logged though. Never had an issue with the car not starting, etc.

Address 16: Steering wheel        Labels: 1K0-953-549-MY8.lbl
   Part No SW: 1K0 953 549 AQ    HW: 1K0 953 549 AQ
   Component: J0527           036 0070 
   Coding: 0013142
   Shop #: WSC 00581 210 83422
   VCID: 010232F958614249E6-8054

   Subsystem 1 - Part No: XXXXXXXXXXX
   Component: E0221           002 0010

1 Fault Found:
00883 - Ignition Switch (D) Terminal S
            012 - Electrical Fault in Circuit - Intermittent

Any one have the same?

I used to have get this error and after an hour of driving my radio would switch off (just pressed the power button and it would come back on).Googling I found some threads where dealers had replaced the ignition switches in TTs that have similar faults. I replaced my ignition switch and the error & issue went away. The switch is not expensive and I found quite easy to replace.

[Dave J]

Thanks f00glee & markrtw. That's very helpful info!

I've never had issues with the radio turning off when driving, or not shutting off when turning off the car. This seems to be just another 'fault' logged, but makes no difference to how the car actually behaves...

[f00glee]

Been a little while since I updated with this cold start splutter.

I ran through all of the "readiness" and calibration sttings in VCDS I could find - no improvement. Also switched out the N80 purge valve as I had read some suggestions that this can cause excess fuel vapor in the intake and a rich condition at startup which can be hard to ignite when cold (this didn't help either).

Strangely, the only thing that seems to help is timing. If I unlock, open drivers door (hear priming), sit straight down, key in ignition and to "on" then wait until the fasten seat belt warning disappears, it starts cleanly first time, 9 times out of 10. Weird! If I stray from this timing a few seconds in either direction it'll almost certainly splutter.

Using this method I'm happier with the starts, but still the illusive underlying cause is at the back of my mind. I also opted not to touch plugs and coils as plugs were replaced 12k ago and coils 25k ago under recall so by all rights should be fine.

I'm now left with inlet cleaning/injector service (pricey but on the list for the future anyway) or perhaps I missed something when logging fuel pressures the other month?

As always - if anyone has any new ideas, share them please! 

[pudding]

When you switch the ignition on, the ECU performs a throttle body check / calibration (you can hear it whining and flapping about).  It sounds like you're cranking it over after this process stops.  Coincidence?  Hmmmmm, not sure.   I haven't noticed a pattern like that on mine, but then again I replaced the throttle last year. 

Have you tried opening the door and firing it up immediately, in the interests of experimentation?   I would say if no amount of ignition on/off'ing (secondary pump priming) improves the situation, it's unlikely to be fuel pump related.

A valve and injector clean certainly wouldn't go amiss, although it's more the injectors than carbon build that's a problem......unless the latter is so horrifically bad, it's restricting air flow.

[f00glee]

When you switch the ignition on, the ECU performs a throttle body check / calibration (you can hear it whining and flapping about).  It sounds like you're cranking it over after this process stops.  Coincidence?  Hmmmmm, not sure.   I haven't noticed a pattern like that on mine, but then again I replaced the throttle last year. 

Have you tried opening the door and firing it up immediately, in the interests of experimentation?   I would say if no amount of ignition on/off'ing (secondary pump priming) improves the situation, it's unlikely to be fuel pump related.

A valve and injector clean certainly wouldn't go amiss, although it's more the injectors than carbon build that's a problem......unless the latter is so horrifically bad, it's restricting air flow.

I have tried jumping in and starting immediately, seems to induce a spluttery start. Its almost as if I've only got a small window between two events in which I have a good chance of a clean start.

Perhaps a slightly carboned up injector which is leaking a bit? Too soon and pressure hasn't built up enough. Too late and I've got excess fuel in the cylinder which is hard to ignite? At this point I'm not so much worried, as I've found a work-around,just hopeful ill stumble across the solution some day. Next time a garage needs to be visited ill perhaps ask them to perform a fuel pressure test with a manual gauge and compare to the cars sensor readings in case there is a mismatch. A carbon clean/injector service at RTech is on the cards, its just finding the time as it'll write a day off.

Picking up on something @maxamplitude10 said a while back. If there any harm to be done by depressing the throttle before the engine is started? If this is perfectly safe ill add this step into my routine and see what happens!

[pudding]

Yeah the leaky injector is a good theory.  Issues like this have an annoying habit of 'fixing themselves' during other work!  Other areas of pressure loss over time are the LPFP, the fuel filter and possibly one of the valves in the fuel rail.

Pressing the throttle before cranking it won't harm anything, but I'm not sure what the ECU does with the throttle during cranking though.  I suspect it 'parks' it in the default position (roughly 6% open) until fires.

[pudding]

Did you get any further with this @f00glee ?   

Mine has started doing something similar recently, and intermittently.   A bit lumpy for a second or 2, or it will fire up immediately, and then cut out straight away.   Probably does that 1 in every 20 cold starts.   The lumpiness 1 in every 10 cold starts I'd say.

I was going to just throw a new lift pump in it and a filter to see if that helps, but thought I'd check to see if you managed to sort it first as the pump isn't cheap!

[f00glee]

Did you get any further with this @f00glee ?   

Mine has started doing something similar recently, and intermittently.   A bit lumpy for a second or 2, or it will fire up immediately, and then cut out straight away.   Probably does that 1 in every 20 cold starts.   The lumpiness 1 in every 10 cold starts I'd say.

I was going to just throw a new lift pump in it and a filter to see if that helps, but thought I'd check to see if you managed to sort it first as the pump isn't cheap!

Not got any further I'm afraid. Still going with the timing solution I mentioned previously. To be clear though, for me the splutter is before the engine has properly caught and fired i.e. during cranking. I never get a cut out after its started and it will always start if I hold the key in the ignition position till its fired properly.

If a clean start is *wer**wer**wer**vrooom* then a "rough" start for me is *wer*wer**spluter*wer*splutter**wer**vroom* 

So may or may not be the same for you - at very least its "similar" so please do report back if anything you do makes a positive difference