Sluggish Cold Starts

[MIJ_JAGGER]

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 

Best description ever lol
Mine has started doing this over the cold weather too recently. It seems to mostly do it when I'm starting up the car for the first time. Doesn't cut out though....
Recently had an issue with the starter motor when the car refused to start one morning, haven't changed it yet but thinking if that's got anything to do with it maybe...?

[Dan_FR]

Mine used to do exactly this... until I bought a brand new Bosch S5 battery.... Hasn't done it in over 12 months since

[f00glee]

Mine used to do exactly this... until I bought a brand new Bosch S5 battery.... Hasn't done it in over 12 months since

Unfortunately, the same didn't cure for me. I had my battery tested to be failing so replaced with varta E44 - no difference in my startups.

[pudding]

Lol, yeah that is a good description    So yours is struggling to get out of bed it seems, so slightly different problems.   Could be fuel, could be spark.....hard to tell sometimes.

Starting up and then cutting out immediately is classic immobiliser failure, but there are no fault codes for that.   I'll use my second key for a while and see if that helps.

Good call on the battery.  I replaced that last year, so I would hope it's not that already!

[antonis42]

mine did this for a while, deteriorated to cranking twice for startup.
turns out it was the fuel filter - has a valve in it -it was not sealing properly,
so would let fuel seap back to the fuel tank and hence no proper pressure for startup. made the lpfp work overtime.
hope this helps

[Dan_FR]

I'm convinced its fuel pressure related. On a cold start, the 5 or 6 BAR (whatever it is) provided by the LPFP is nowhere near enough to fire the car up, and the pressure must build. Now whether the car sometimes waits for the full 50 BAR, and other times it attempts to start up before it is reached, I do not know.....  Many variables to consider.....

What I did notice with mine is how much faster the starter turns with the newer battery compared to how it was previous.

[Dave J]

Hmpf - mine seems to do the exact same thing. Some days I jump in & it bursts into life, and other times it splutters into a grumpy start.

Mine's had a new LPFP in the last few years, is running a LOBA HPFP, R8 coils, a fresh Varta battery, recent service, new 6.6 bar fuel filter and it still sometimes crunks in to life. I'd like to see if injector cleaning & walnut blastings sorts this. The mornings when it bursts to life are great...!

[pudding]

Mine started immediately this morning, and then cut out straight away. Fired up and stayed running the second time. 

I will try one of the new 6.6 bar filters as well.  Start with the cheapest bits first 

[Neil 54]

i have this problem to i have changed HPFP, LPFP ,Fuel filter,injectors cleaned, inlets cleaned, coil packs and plugs changed still the problem exists really not sure where to go next have read on TFSI facebook site about drilling out one of the brass fittings on HPFP to allow more fuel through saw a post from Niki at RTech who said it would have benefits at any stage of tune was thinking may also help with this

[pudding]

I believe some uprated HPFPs already come with a bored out fitting (such as Loba) but that's probably not a bad idea.   

The last 3 cold starts have been spot on for me.  Weird.

What I have noticed is in when it's minus degrees outside, it starts perfectly.  When it's in the zero to +5 range, that's when it can muck about.  All engine maps have start up fuel tables based on temperature, so maybe the 0 - 10 range is slightly weak. Dunno, just a hunch.

[Dan_FR]

Won't help with the cold start, but it should make life easier for your LPFP on a daily basis.

I've never actually checked my LOBA to see if I have the larger fitting. It's been on the car for 3 years now. Job for next year once it warms up

I've noticed with mine, that sometimes when its sub zero it also doesn't idle 'high' like it does when its slightly warmer... It just starts and ticks over at around 800rpm. But I will say when mine did have this issue it was always the 0-10 range of temps it played up - never sub zero and never when it was warm out (over 10 degrees)

I am almost sure it was my new beefier battery that resolved it for me. Have any of you guys ever logged the cold cranking speed of your engine? Disable it from starting and log it with VCDS to see what the cranking RPM is and how quickly it reaches this speed

[pudding]

Mine's like that as well.  When it's really cold, the idle is much slower, to the point of feeling it through the uprated mounts.  Normally I can't feel the idle at all.

My R32 was exactly the same.  Apparently ME7 and MED9 ECUs doesn't have fixed idling routines.  The idle speeds vary depending on SAI/EGR/HVAC/Temp dependencies but it is weird how in the summer it cold idles at 1200rpm pretty much every time, but when it's -5 to 0, it rarely idles over 1000.   Must be an air density / emissions modelling thing.  Not sure.

Thankfully our winters aren't long enough for it to be a huge concern!

[pudding]

I may have stumbled onto something today.    I've noticed since the Revo 2+ tune (with Revo intake) my long term part throttle trims were +8%.  It shouldn't be that high with software tailored to the intake, and especially not after only 3 days of running the tune.....and even more especially not when running B9, T5, F7.  That's a pretty rich AFR request.

So anyway, out of curiosity, I shoved an old MAF in (it's about 3 years old) on my lunch break and since then it's driven a lot better.  Smoother, quieter, more responsive.  All of it.
I will see if stone cold startups improve also.

The previous MAF was bought this summer from VW.  It was covered in engine oil when I took it out to pop into the Revo intake, which I can only guess came from excessive turbo surge.  There is no oil in the dump valve pipe work.   Since the MAF is very close to the rear PCV and the turbo, excessive turbulence down there will back flow oily air onto the MAF.   I guess it's f'cked then.   Sensitive little things.  I will see if I can get VW to swap it out for a new one since their parts have a 2 year warranty.

That was a long winded way of saying - iffy cold starts could be caused by a dodgy MAF.    MAFs are funny things.   They can show no apparent problems, small trims, no fault codes.....and yet.....stick a new/old one and the engine completely changes for the better.   Stupid things.  I always preferred engines that use MAP as load instead of flakey MAFs.

[f00glee]

I may have stumbled onto something today.    I've noticed since the Revo 2+ tune (with Revo intake) my long term part throttle trims were +8%.  It shouldn't be that high with software tailored to the intake, and especially not after only 3 days of running the tune.....and even more especially not when running B9, T5, F7.  That's a pretty rich AFR request.

So anyway, out of curiosity, I shoved an old MAF in (it's about 3 years old) on my lunch break and since then it's driven a lot better.  Smoother, quieter, more responsive.  All of it.
I will see if stone cold startups improve also.

The previous MAF was bought this summer from VW.  It was covered in engine oil when I took it out to pop into the Revo intake, which I can only guess came from excessive turbo surge.  There is no oil in the dump valve pipe work.   Since the MAF is very close to the rear PCV and the turbo, excessive turbulence down there will back flow oily air onto the MAF.   I guess it's f'cked then.   Sensitive little things.  I will see if I can get VW to swap it out for a new one since their parts have a 2 year warranty.

That was a long winded way of saying - iffy cold starts could be caused by a dodgy MAF.    MAFs are funny things.   They can show no apparent problems, small trims, no fault codes.....and yet.....stick a new/old one and the engine completely changes for the better.   Stupid things.  I always preferred engines that use MAP as load instead of flakey MAFs.

Interesting idea. Is it perhaps worth me unplugging my MAF when I'm home tonight and see how the car starts in the morning with it disconnected?

[aaronk.juju]

My ED30 occasionally struggled to start, and had to be cranked for a good few seconds. Although the cranking would go weak after a couple of seconds it would always start. I checked my battery voltage, which was healthy. I suspected possibly the starter motor/bad connection. However I cleaned my intake valves (just a job I was planning on doing anyway) recently and have not had any hesitations in starting since this has been done. Our cars have a major issue with this buildup. My runner flaps, and valve ports were coated in about 2-3mm of gunk (2-3mm either side of the runner flaps so they were over double their normal size!) which I can now see would cause problems with starting. My car had only done 73k and the buildup on the valves was ridiculous.