01 ALH - Hard Cold Starts - Rough idle and diesel smoke until warm - VCDS

walrus

Member
Joined
Oct 9, 2024
Location
Eugene OR
TDI
2001 Jetta ALH
Just got my VCDS hooked up for the first time and have a compression tester on the way so that I might be able to get the necessary info to pin down my issue!

Hard cold starts - harder with cold ambient temps (30~deg F), but still hard when fair temperatures (50-60deg F).
Turn over for 10 seconds or more and sometimes it still doesn't start.

Installed a manual glow plug momentary switch to help cold starts and avoid the excess wear on my starter and ring gear.
Currently mid 30's F and 4-5 seconds of glow plug allows it to start right up.

Lots of diesel smoke for 5 minutes or so of idling, then mostly clears up - at least gets much thinner/less.
Sounds fairly rough - possibly like a misfire during this time - then smoothens out after 5 minutes of idling or driving a couple miles.

Bought this 01 Jetta a few months ago and been commuting daily - 35-37 MPG running it a little on the fast side - seems like this might be lower and point to something.
Fires right up after only sitting for an hour or so even in this colder weather.
Injection pump and injectors and filter were replaced with used replacements from previous owner at a "VW mechanic". They were also having smoke and hard start issues, so this replacement doesn't seem like it solved anything and they are of unknown condition to me. I do have the receipt for this work.

What should I check with my VCDS to start pinning this issue down?
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
My #1 test would be timing. Will be a little tricky in cold weather, as the coolant temperature has to be at least 80C, but it would be my #1 suspect.

My #2 test would be compression. Not a VCDS thingie, but a very common cause of hard cold starts with lots of smoke, and a good thing to rule out before you spend more time and potentially money digging deeper.
 

walrus

Member
Joined
Oct 9, 2024
Location
Eugene OR
TDI
2001 Jetta ALH
My #1 test would be timing. Will be a little tricky in cold weather, as the coolant temperature has to be at least 80C, but it would be my #1 suspect.

My #2 test would be compression. Not a VCDS thingie, but a very common cause of hard cold starts with lots of smoke, and a good thing to rule out before you spend more time and potentially money digging deeper.
I will look into testing the timing. Any tricks on testing in this cold weather? I'm thinking cabin fan off to start, wait for a day that's a bit warmer, anything else?
Any specific articles you recommend on the matter? Otherwise, I will see what a search can warrant.

Compression tester should be here in a week or so, so I will do that ASAP!

Thank you for the help.
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,glutton for punishment got another tdi 2001NB,another yellow tdi NB , added an 06 NB DSG
As Vince said, do those steps first , with any lick just the timing is off . The lock down tools would be very helpful particularly the cam lock. You can get away with a drill bit for the IP pin ( not sure of the size ). And don’t necessarily need the crank lock as long as you can keep an eye on TDC through the inspection hole.
Just make sure all accessories are off and engine is up to temp an select the correct year for your engine.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Yup, although no need for locking pins etc if you're just going to use VCDS to measure your current timing. :)

In terms of heating up the engine so that it's warm enough to accurately read the timing, I tend to:
- have a cold front on the rad
- no cabin heat, as you mention
- ride 'er hard on the highway, for at least 10 minutes, then pull over somewhere safe and read the timing before the engine cools off at idle.
 

walrus

Member
Joined
Oct 9, 2024
Location
Eugene OR
TDI
2001 Jetta ALH
csstevej and Vince Waldon,

Thank you for advice! I will look into getting or make shifting a cold front. Seems like it would be a good idea to have anyway. Then hopefully I can manage to get an accurate reading one of these next days when its in the 40Fs.
And I will test compression when I get the tool delivery as well and report back.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
All of what I said being said, I live in the Great White North where winters tend to be pretty extreme and hence one has to use every trick to get the coolant warmed up all the way.

People that live in warmer climes may only need 10 minutes on the highway.
 

walrus

Member
Joined
Oct 9, 2024
Location
Eugene OR
TDI
2001 Jetta ALH
Got it! In the PNW here, and we're having a little cold snap in our terms. Which is Lows in the 20s for a couple weeks. The 'dummy gauge' as I've seen it called only goes up about a quarter of the way on my 15 minute commute which is 60-70 mph most of the way. Heater is only luke warm by the time I get to work.
I already have some pipe insulation laying around so I was thinking about trying that in the grills for starters.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Another thing to check with the VCDS is the various temperature sensors. They should read close to ambient temperature when cold, higher when engine is warm. You're looking for wack numbers to indicate failure.
 

Zak99b5

Veteran Member
Joined
Apr 30, 2021
Location
Albany NY
TDI
2003 Jetta TDI
Got it! In the PNW here, and we're having a little cold snap in our terms. Which is Lows in the 20s for a couple weeks. The 'dummy gauge' as I've seen it called only goes up about a quarter of the way on my 15 minute commute which is 60-70 mph most of the way. Heater is only luke warm by the time I get to work.
I already have some pipe insulation laying around so I was thinking about trying that in the grills for starters.
That sounds like a stuck-open t stat to me.

In the 20's it takes about 7-8 minutes for my car to get to “temp” on the idiot gauge. It barely moves for the 2 or so miles of city, but when I hit the interstate spur going 65-70 it chugs right up to 12:00.
 
Top