Freezing Cold Start = stalling & no throttle - only when cold

[muff1991]

Hi All, so I wrote a post a few months back about my GTI starting and then cutting out, I said I'd report back when I own VCDS.. well I now own it but need help diagnosing my issue please!

my issue: when the weather is sub zero I'll come out to the car, start it... and it starts on the button no problem. it idles for a few seconds then just cuts out. sometimes it will idle for longer sometimes only a few seconds. while the engine is idling and I press the throttle pedal.. NOTHING happens!

if I push the throttle pedal down slightly and then start the engine, the throttle works.. if I let go of the throttle the revs will drop and then engine dies. and also once I've let go of the throttle and then push throttle again it wont work.

when the weather is above freezing say 2 degrees, car starts and idles, and throttle works! however, the throttle response is LAGGY as hell and stupidly unresponsive. as in, I can touch the throttle for a good few seconds before it works and then it does but revs slowly climb and then once it gets past 2k the revs will shoot up! When I drive off the car is so unresponsive its unreal.. but as the car warms up this almost goes away. its only a cold weather thing! I think I did describe this like.. Imagine driving at say 30mph in 6th gear and then full throttle it would be laggy and unresponsive right.. then as the revs build up and turbo kicks in your off. its like that but in all gears driving normally! best I can describe it.

so I scanned the whole car with VCDS and had back a couple of little faults but nothing that says to me it has anything to do with this issue (was things like.. HVAC refrigerant, rear bass speaker open circuit, central locking - light switch)

after doing that, I realigned my throttle body just to rule that out as cleaned it a few weeks back, made no difference. so I brought up a couple of measuring blocks and looked at:
throttle pedal sensors, throttle valve angle sensors, all seem to be doing fine with ignition on and engine off!

but this is the bit I don't understand: when I start the car on idle and push throttle pedal down the throttle pedal sensors do there bit but the throttle valve sensors DONT move! this would explain why when I push the throttle down the engine isn't revving! I don't want to immediately think throttle body as it works fine with ignition on engine off? and of course once the weathers warm it all ok too.. its only when its freezing the engine cuts out!

it's literally like something somewhere is freezing and once the engines started the ECU is like nope... cut! I was told to check the Coolant Temperature sensor readings.. which showed 0.00 and temperature was -0.5 so I would say a tolerance of -1/+1 is fine right.

thanks for taking the time to read yet another essay from me.. I am open to any advice you can all offer, what else should I be looking at within VCDS.. shall I log this and post it up? thanks.

[muff1991]

FIXED..

To be honest, the below is irrelevant to most if not all of you on here, but i hate it when people dont post there results and fixes - especially if another member has given advise and it fixed it for them, yeah cheers mate    I am not one of those and i'll sure share anything i have to offer!

For some of you that may remember, i was experiencing and B*&tching a lot about my GTI having 4000rpm power cuts & stalling when cold temps was around. ONLY when cold.. if temps was above 10 degrees, no issues with power or stalling. To be more specific, if the ambient temperature was less than 10 degrees i would get power cuts almost like someone instantly turned the turbo off around the 4000rpm range. around 5 degrees or slightly lower the car would be really hesitant pulling away up until 1.5-2k rpm then it would be fine (then cut at 4000 lol) if the outside temp was 0 degrees or in the minus' the engine would start, idle then cut out and there wasn't anything i could do about it.. the throttle was completely disabled and wouldn't do anything! I also had really really bad turbo flutter but like a squealy screechy turbo squeal.. it would cha cha cha cha and then psshhh slightly at the end.. it done my nut in, was embarrassing! it wasnt even a nice flutter. it was almost like the DV wasn't working or delayed for a few seconds.

Anyway, in an attempt to find the fault.. i purchased VCDS at the start of the year to help me diagnose, but everything to my knowledge would match up and seemed to be working fine, i just couldn't work out what was going on. i crawled over the car trying to find anything mechanically wrong and couldn't. replaced all the common and some not so common parts and nothing made a difference. The only weirdest thing i came across that temporarily helped with every issue above was, if i disconnected the Intake Air Temperature sensor the car wouldn't stall in freezing temps, the throttle worked just fine and i had no power cuts at 4000rpm, the car drove absolutely fine (still had the annoying chatter) which made me sure, nothing mechanical was wrong and it had to be electrically related or at worst.. software related (map)!!

I do have a Ram Air intake and some people said the flutter would have been normal, but my mate and cousin both had the same car with the same intake and only ever had the "ppsshhh" never a flutter. so i couldn't see why mine would be any different. I always had a feeling the car had a remap but the previous owner said it didn't to his knowledge.   after getting @Pudding to read logs, help me diagnose, give me some pointers and advise me on where to look in VCDS to see if my engine had been flashed for sure.. we discovered it indeed had been mapped.

The chances of a map being corrupt is slim, but i didn't ignore this, i wanted to fully check the car to make sure i wasn't missing anything before having the map removed and ending up with the same problem only the car would be slower.

Well in the end, i couldn't figure it out.. the same issue kept pointing towards software or something electrical.. so i bit the bullet and took my car to a local garage to have a stock map file flashed onto the ECU so i can start again with a blank canvas! The result was brilliant!

I drove off down the road with NO turbo flutter/chirpy squeals or weird screechy flutter noises changing gear and releasing throttle. All i hear now is "ppsshhh" which is expected and im happy with that (its not blow off loud) its resonated through the intake loud and im defo happy with that.

The day i had it done was 5 degrees, so blasted it.. NO power cuts at 4000rpm.. pulls right through fine.

couple of days later it was -2 in the morning, started the car up.. engine run fine and didn't stall, throttle was NOT disabled and everything worked just fine.

more than happy and satisfied to say.. ALLLLL along, i had a bad map on the car (Shyyytttt software) or as @Pudding said and i agree, the wrong map for the car was loaded on.. hence some issues! It's all fixed now though

Its really smooth now, the only downside is the power, i feel like im running 150hp not 200. i guess thats what a remap (@ 230-240 ish) spoils you with. i am going to smoke test and boost leak test to be sure its where it should be as i would say it feels slightly under powered and less punchy. i also need to do the inlet carbon clean (147k its way past needing it) and i experience a little rev hang still, so power and rev hang is my next mission but in no rush for now.

who would of thought it was software all along ey! thanks for reading if you made it this far. not a problem many people would come up against, but for those who ever wondered what was wrong with mine in the end... here you go lol enjoy  

[pudding]

Normally the software is the last thing I'd point the finger at, but in this case it had us chasing our tails!

Messing up the basic functions of the map really is next level incompetence.  All that needs touching with remaps is fuel, boost and timing.  Everything else should be left well alone as that is the stuff VW spent millions on perfecting!  And yeah, I can't be certain, but if they uploaded an ED30 map to a GTI for example (if it's even possible?) that would almost certainly cause severe cold running issues!

Glad it's finally sorted mate 

[muff1991]

Thanks pudding, we got there in the end. I still can’t believe it was software in the end.
Thanks again for your help in trying to figure this out. :-)


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