BEW No gas pedal response on cold start

bmw

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Dec 23, 2018
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Ontario
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Mk4 Jetta Wagon BEW
Hey guys, first time poster long time lurker here, got a bit of an annoying issue here I've been trying to diagnose for over a year now, I've tried searching many forums, all the info I've found has either been inconclusive or hasn't solved my problem. I'm hoping one of you guys may have some insight, and either way I'll update this thread with the answer once I find it because it seems like a lot of others are having the same or similar issues.


My car is a 2005 Jetta Wagon with BEW, 380k Kilometres on the odo, basically after 3 years of ownership it started doing this thing where on a cold start the gas pedal won't work at all, to elaborate on this, I mean the RPM will stay at 1100 rpm until the car "warms up" and you can mash the gas pedal and it won't touch the RPM even the slightest, it'll sit unoperatable for like 5-10 minutes before it "warms up". Weirdly enough this only happens when its below 10 degrees celsius outside. I've checked VCDS and have no faults in any control units, the VCDS reads the accelerator pedal position sensor being actuated perfectly fine from 0-100%, also shows "throttle position" at 95%, compared this to a known good car and it looked the same. Apparently the throttle position sensor is built into the gas pedal so I threw a new gas pedal in it just on a whim since the other was original and super old, nothing changed. A couple other weird things can be seen, my EGT will randomly spike to 1100 degrees while cruising at highway speeds (+100 km/h) (could be an issue with the gauge maybe unrelated), and finally, sometimes when pulling off from a standstill, example like turning in a busy intersection, it feels like the car will randomly like maybe 40% of the time go into limp mode and drive super slow like it's barely pulling its own weight, once again though, no dash lights, no fault codes, nothing. then it suddenly after like a minute or so once I'm halfway in the intersection about to cause an accident, it'll pop right back to behaving normally. other than these issues the car drives totally normal and after the car has warmed up once in the morning the other times i start it throughout the day may or may not trigger the "Dead pedal start".


The previous owner provided me with a receipt showing the turbo, intake manifold, egr system and throttle body had all been replaced in 2015 at 305k kilometres odo. and i bought it at 320k. I've done a lot of work on the car since owning it, like replaced all vacuum lines, new n75 valve, replaced all filters, brake light switch, clutch switch, removed the EGR system, changed exhaust and got a malone stage 1.5 tune done. I don't know for certain but after checking everything on VCDS and seeing that everything looks normal, I think the tune may be causing the issue, but the guy that originally did it basically disappeared. It was done at a reputable shop and I had no issues with it last winter, it seems like it happened after disconnecting my battery when I did my clutch and I didn't notice until the weather got cold enough, but that could just be a coincidence. Since it happened I applied vacuum to the turbo actuator and it seemed to move freely, checked the ASV, its working fine, checked all vacuum lines, no leaks, checked MAF plausibility in VCDS. The only slightly weird thing in VCDS is that my specified boost pressure is about 50 mBar more than my actual, compared with my friends working tdi his is about 20 mBar off, could it be that my actuator needs adjustment and maybe the car is triggering limp mode from overboost as soon as I touch the gas and with the high idle this cuts the throttle?


I've contacted someone else who's going to revert it to a factory tune after the holidays, but I was wondering if anyone else has any ideas if this does not fix the issue, or any insight on anything else to check that I may have missed. Thanks in advance and sorry for the long read lol
 

oilhammer

Certified Volkswagen Nut & Vendor
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Dec 11, 2001
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outside St Louis, MO
TDI
There are just too many to list....
Sounds to me like the ECU is randomly seeing a brake pedal apply signal and doing exactly what it is supposed to do: return to fixed high idle.
 

bmw

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Ontario
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Mk4 Jetta Wagon BEW
Sounds to me like the ECU is randomly seeing a brake pedal apply signal and doing exactly what it is supposed to do: return to fixed high idle.
In VCDS it shows the brake is not applied, I went ahead and replaced the switch anyways because I read that it fixed someone else's, but no luck. The car starts with the 1100 idle but then after like 5-10 minutes to goes back to normal. I should've specified but the high idle is from the tune to help with cold starts since i'm in Canada
 

oilhammer

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outside St Louis, MO
TDI
There are just too many to list....
BOTH circuits not applied, but when you do press the pedal they BOTH change properly?

Perhaps there is a problem with your software?
 

bmw

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Mk4 Jetta Wagon BEW
BOTH circuits not applied, but when you do press the pedal they BOTH change properly?
Perhaps there is a problem with your software?
Exactly, the brake switch will show either applied or not applied, its working as should, and the pedal will show a percentage value of how much is being applied, both seem to look like they're working in VCDS despite the gas pedal not working. I'm hoping you're right and it's an issue with the software, I'm going to get it reverted to stock tune tomorrow and see how it starts Saturday morning
 

Nero Morg

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Random thought... It doesn't work until warm.... Maybe fuel inlet restriction? Possible fuel gelling, but when it warms up it flows better? Wouldn't hurt to check.
 

bmw

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Mk4 Jetta Wagon BEW
Random thought... It doesn't work until warm.... Maybe fuel inlet restriction? Possible fuel gelling, but when it warms up it flows better? Wouldn't hurt to check.
The fuel filters old now that you mention it that totally slipped my mind, its about 2 years and 60k old, other than that where would I check? Like pull the fuel pump in the tank and look inside the tank? I also did run fuel additive in the previous winters so you could be right, although it hasn't got below -10 celsius yet. It's 13 degrees celsius here today and the car started perfectly fine. I went and got it tuned back to a factory tune so we will see what happens next time it's cold out. Going back to factory made me realize how much power the tune adds, the car is SLOW now lol
 

Nero Morg

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I wouldn't imagine the tune had anything to do with your issue. I would definitely replace the fuel filter, and pull the sending unit and clean it. I did the same on my ALH and it's incredible how much debris collects on it. Yours will be a little different since you have the electric pump, but just make sure the screen filter isn't all plugged up. And be careful not to bend the level sending unit!
 

Vince Waldon

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Exactly, the brake switch will show either applied or not applied, its working as should
Just being doubly sure... since it's bit people in the butt before... but OH is asking if you're seeing BOTH brake light circuits open and close.

The brake switch has two independent switches... each of which are monitored independently by the ECU and each of which have its own status bits on VCDS (group 006, field 2, bits 7 and 8)

If the ECU detects *either* set of contacts and the throttle at the same time it will hold at a fast idle.

Outside chance, I know, 'cause you've replaced the brake switch... but just being clear in case there's a wiring issue you don't know about.
 

bmw

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Mk4 Jetta Wagon BEW
Well boys it was -1 degrees celsius today in Ontario, she started up and gas pedal working mint right away on factory tune. I still think disconnecting my battery corrupted the tune or something like that, or maybe it just isn't cold enough. A friend of a friend installed a stock file plus egr delete just so I can see if it throws a CEL so we'll see how it goes once the weather gets colder. I'm gonna order up a fuel filter too just for the hell of it, i've noticed the fuel economy go down a bit
 

Nero Morg

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Interesting. Well anything is possible, glad you got to the bottom of it.
 

bmw

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Just being doubly sure... since it's bit people in the butt before... but OH is asking if you're seeing BOTH brake light circuits open and close.
The brake switch has two independent switches... each of which are monitored independently by the ECU and each of which have its own status bits on VCDS (group 006, field 2, bits 7 and 8)
If the ECU detects *either* set of contacts and the throttle at the same time it will hold at a fast idle.
Outside chance, I know, 'cause you've replaced the brake switch... but just being clear in case there's a wiring issue you don't know about.
Thanks Vince, I honestly didn't know that, maybe I should call up my buddy with VCDS and give it a double check. I remember only seeing one value in whatever block we were looking at, just saw it working and didn't pay too much attention to it after that
 

bmw

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Interesting. Well anything is possible, glad you got to the bottom of it.
Yeah knocking on wood lol. Maybe it just is a coincidence that it's working today and -1 just isn't cold enough to exacerbate the issue, we shall see
 

~TDIguy~

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Romulus Ny
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2005 Jetta Sedan
I randomly have the same problem with my 05. On a cold start sometimes it will idle for several minutes with no throttle response whatsoever. However I found if I shut it off and restart it will work normally right away. Doesn't do it every cold start but fairly often. It did it when I had my stage 2 Malone and still does with my Stage 4. Any reason it would do this only when cold and not when its warmer? I never really worried about it but saw this thread, would be nice to find an answer:D
 

Nero Morg

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If it happened with his tune, and two of yours, might be a question for Malone, I know I'm interested in the answer.
 

bmw

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Update, this morning was -1 degree celsius, car started perfectly fine and gas pedal worked perfectly fine again, however as soon as i finished moving the pedal to see if the idle would change (it did) the car died. I started it back up again, it would run fine again then as soon as I reved it and stopped again it would die again. Seems like its a fueling issue to me, however no fault codes or nothing. After like 5 minutes time of screwing around with it and doing this, like maybe 3-4 ignition cycles, the car started behaving like normal again. I'm going to grab a fuel filter from the dealer tomorrow and put it in and see how it goes, but yea the no pedal response seemed to be directly correlated to the tune it seems. I've emailed the guy who initially did my tune again, we'll see if he replies
 

bmw

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Update, it was -7 degrees celsius this morning, car started perfectly fine and and pedal response was working. Seemed to have no power starting from a stop at first, but once I got her going it was totally fine for the rest of my drive and then starting it several other times later in the day it was totally normal. New fuel filter and T fitting for it are going in tonight, I'm gonna run some diesel kleen too and put a full tank of shell vpower. Still haven't been able to get ahold of the guy who originally did the tune, going to try to contact Malone to see if he can fix the tune and then have my buddy reflash it back on.
 

~TDIguy~

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New fuel filter and T fitting for it are going in tonight, I'm gonna run some diesel kleen too and put a full tank of shell vpower.


I dont know how yours is acting but my car is definitely not a fuel supply problem from what i can tell.. I think its something in the software somewhere...
 

BobnOH

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central Ohio
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Just to rule out dumb stuff, I would check all the various temperature sensors cold and hot, you're looking for wacky values.
 

rennsportmotorrad

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Port Orange Fl
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2004 Jetta TDI wagon
I run diesel kleen in every tank at fillup, cant hurt -and as for the fuel filter on my 04 Jetta Wagon PD I change the fuel & air filter every 2nd oil change--it's so easy to get too -takes 5 min and they are not that expensive --Granted I dont have to deal with real cold weather here in Florida, but If I lived in the great white north I would be using some antigel in the fuel in winter for sure
 

bmw

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Mk4 Jetta Wagon BEW
I dont know how yours is acting but my car is definitely not a fuel supply problem from what i can tell.. I think its something in the software somewhere...
That's what I thought as well, but ever since putting it back on the factory tune it will intermittently have no power on start up. The weird thing is though once I get it going it doesn't skip a beat and you would never guess there's anything wrong with the car. Today was -1 celsius again, car behaved totally normal, however the other day as I mentioned before it would basically stall right away unless I held the gas pedal down until it had "warmed up" for a couple minutes. Still no faults of any kind logged, Ive checked all the values in VCDS to see if anything seemed off but it all looked normal. I finally picked up the fuel filter and everything I was planning on trying this evening, going to put it in tomorrow morning and see how it goes. I'm going to pull the sending unit in the tank and inspect it as well, it does have 380k now, maybe its slowly on its way out. Just so weird how once I start driving the problems just disappear
 
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Nero Morg

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I'm glad reverting the tune fixed it. Sure was a strange issue. As for the needing to throttle it until it warms up, I can't help you there as I don't know enough about the BEWs. If I had to guess based off of similar engine designs I'd say air in fuel.
 

bmw

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Update, looks like the tune is unrelated, I changed the fuel filter, put some diesel kleen in the tank and filled up with shell v-power and on my way home back from a friends house last night the car had no pedal response on initial start up, I turned it off and back on again and the problem went away. It was -1 degree celsius so it seems as if there's no direct correlation to the cold and it was just in my head, I thought that for sure I had fixed it as when I replaced the fuel filter I had noticed both the feed and return lines routed from the filter to the hard lines on the passenger side by the strut tower were both kinked, I fixed them to a more natural position and thought that would be the end of it. Looks like I'll be pulling the fuel pump once I empty the tank and have a look in there, this issue is driving me nuts lol
 

shanky887614

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did this start after a timing belt/cam change by any chance?

Sent from my ASUS_X00ID using Tapatalk
 

bmw

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Mk4 Jetta Wagon BEW
did this start after a timing belt/cam change by any chance?

Sent from my ASUS_X00ID using Tapatalk
No, I had the timing belt and water pump done at 330k in my first year of ownership. I have owned the car going on 4 years this summer, the issue started happening last winter at around 360k, I've inspected the camshaft last winter as well when I fixed the leaking valve cover gasket, there was minimal wear, the only work I had done on the car around the time the issue started happening was the clutch & EGR delete, I simplified the vacuum line system when I removed the EGR however I doubt this has anything to do with it as the turbo operates as it should whenever under load and the car drives fine once I get it going.


This morning was 1 degree, I started the car, no pedal response and it immediately died just like the time I mentioned in a previous post, I restarted the car, pedal was then working intermittently and RPM was jumping around inconsistenly, if i let go it would hover around 500 RPM which is way lower than I've ever seen it, I held the pedal to the floor and was able to keep it running at a high idle around 1200 RPM, the throttle response then spiked after holding this for about 45 seconds. I then let go of the gas pedal and it went back to a normal idle like 850 RPM, I tried to drive off and the car stalled, like no power at all. I restarted it, held the RPM higher, around 1500 and drove off normally. Went to the store, came back to the car and it behaved perfectly normal again. Seems like there is no pattern whatsoever on what causes this issue, its sporadic, sometimes nothing will happen at all and it will be like the car is fixed, and other times this will happen, or it will run fine and just the pedal wont work, there's no consistency at all.
 

bmw

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I am almost certain at this point that its a fueling issue, as it seems that the only time there are issues are on first initial start up after the car has been sitting for longer than 8 hours, and requesting load from a standstill, all my soft lines are new, I don't want to just throw any more parts at the car though, I'm going to pull the in tank pump and inspect it regardless once I burn through this tank.

Update: for anyone else diagnosing the same issue, I found this very useful post http://pics.tdiclub.com/data/517/PD_fuel_delivery_check.pdf
I just performed a couple of the checks, I noticed when cycling the key with the back seats removed the lift pump does not make any noises whatsoever, I don't want to jump the gun and am still gonna test the flow once I empty my tank. I also found a little bit of dried up diesel that has leaked out from what looks to be the fuel inlet on the tandem pump (closest to the front of the vehicle). Another thing I noticed, not sure if this is normal or not, but if I pinch the vacuum line from the N75 that goes to the turbo actuator the N75 starts making a loud buzzing noise, not sure if this is simply because it's on the other side of the 1 way check valve and there's no where for the air to go or maybe something is internally wrong with the N75, I'm going to switch it with the other one that was previously used to control the EGR and see if anything changes.
 
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aje9639

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Salt Lake City
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2004 Jetta TDI
My '04 Jetta BEW does this exact same thing. Usually happens in temps around 10-25 degrees Fahrenheit (Utah doesn't ever get super cold). All I've ever needed to do was shift the car back to park from drive, and then re-shift back to drive and it's fixed itself. I too can smash on the gas pedal as much as I want, but until I shift it in and out of drive, will it work again. Maybe a different problem than OP, but same symptom. Only happens about once a month and never bothered me enough to get it looked at.
 

bmw

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Update: this morning was -4 degrees celsius with windchill feels like -15, by far the coldest day this winter, however today the car started up and idled perfect, pedal response was there. Upon putting it in gear and attempting to drive off I noticed the complete lack of power, it almost wanted to stall but I mashed the pedal to the floor and held the clutch in a little more to keep her going, it didn't die and once I got driving it was fine.

It's so weird that it happens sporadically like this, I almost want to believe it's unrelated to the cold due to it being fine on the coldest day today, however in the spring and summer months the gas pedal never has any issue and has never once done this. I do still notice the "loss of power" when accelerating from a standstill in the warmer months, however it happens intermittently and only when starting from a complete stop.

I almost want to just order a new in tank lift pump at this point, can anyone confirm that if I don't hear any noise from it when cycling the key its faulty? It would seem totally plausible to have this loss of power when starting from a stop with a failing pump, however I would assume that I would notice it being starved for fuel in the higher RPM range or when flooring it at highway speeds, etc. I wish these cars were smarter and could atleast give me one fault code to lead me in the right direction, seems like im just shooting in the dark at this point.

I'm going to do an oil and air filter change, and swap out the N75 for the EGR controller valve today, see if that buzzing noise from the N75 when blocking the turbo actuator vacuum line is normal or if my N75 is bad, will update on findings
 
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BobnOH

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central Ohio
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,,,,,,,,,,,,,,,,,, can anyone confirm that if I don't hear any noise from it when cycling the key its faulty?..................
It will make a noise when cycle key on. The thing on these PDs, seems the tandem pump still sucks a bit and allows the car to run. Often folks let it (in-tank) go and eventually the tandem pump fails.
 

~TDIguy~

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May 4, 2017
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Romulus Ny
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2005 Jetta Sedan
So I noticed something about the no throttle response on my car today when I was trying to make a quick run to town... It didn't have any response in the initial warmup, ya know how they rev up to 1000-1100 for a bit right after a cold start? Both this morning when I left the house and then at lunch break and again at the end of the day it did the same thing. No response till it throttled back to regular rpms then everything is the same again... Which kinda sorta makes sense, don't be driving or revving it till it gets the oil moving etc etc???? But I don't know why some of us have the symptoms and others don't.. But it reconfirms my theory of it being a software thing.

Oh and the temp this morning was in the teens Fahrenheit and in the 20s later in the day...
 
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