ALH cold start issue

turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
Hi there! I have a rough start issue first thing in the morning with my newly acquired 03 Jetta with 192k miles. The car takes only a couple seconds of cranking to start but runs rough for about 10 seconds and then smooths out. This doesn't seem to make a difference whether it's 40F outside or 60F. I've eliminated the thermostatic tee, drilled out the check valves in the fuel sending unit, ran new fuel lines under the hood, new fuel filter, new updated MAF, ohm'd all glow plugs to be 1.9 ohms, tested glow plug harness, verified coolant temp reads the same as intake air temp and fuel temp. Timing is dead on, IQ is ~3.5 at hot idle. No engine codes in the VCDS. Not sure where else to look. Any help would be appreciated!
 
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mr.loops

Veteran Member
Joined
Nov 24, 2010
Location
Kelowna
TDI
2002 jetta, 2003 Bora 1.8T
My freshly built ALH had a bad cold start stumble first thing in the morning ( lasted around 8 seconds). Starting it warm, I had no issues what so ever

Turns out my static timing was out a tad. Your belt might be stretched causing this rough start.

How do you confirm yours? Did you use the proper tools (cam plate and IP pin) or did you just do a visual check?



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turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
My freshly built ALH had a bad cold start stumble first thing in the morning ( lasted around 8 seconds). Starting it warm, I had no issues what so ever

Turns out my was my static timing was out a tad. Your belt might be stretched causing this rough start.

How do you confirm yours? Did you use the proper tools (cam plate and IP pin) or did you just do a visual check?



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I checked it via VCDS
 

Fahrvegnugen

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Joined
Jan 21, 2017
Location
Burlington Vt
TDI
01 golf 1.9 alh gls silver
A couple of cranking seconds on cold start makes me wonder about or starter or battery. Of course it could be something else but that would be checked later
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
The fact that it runs rough for 10 seconds makes me think maybe there is a small leak in the fuel system. Once running the air dissipates.
 

jmodge

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Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 5speed daily commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/502's backroad cruiser
Have you gone to advanced measuring blocks checked your speciified against actual timing during this period.
 

jmodge

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Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 5speed daily commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/502's backroad cruiser
As mentioned above, it does start on static timing before the ecu takes over. Maybe bump it around and see what happens
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
Diesel purge, closed loop system and see if that helps

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turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
A couple of cranking seconds on cold start makes me wonder about or starter or battery. Of course it could be something else but that would be checked later
Maybe I wasn't clear. It fires off right away and just runs rough once it's started. It doesn't have a starting issue, more a running issuem
Have you gone to advanced measuring blocks checked your speciified against actual timing during this period.
No, I've yet to explore the advanced measuring blocks but I'll have to do that.
Diesel purge, closed loop system and see if that helps

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Already done that with no improvement
 

Nero Morg

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Joined
Oct 19, 2017
Location
OR
TDI
2003 Jetta wagon, 2001 Jetta TDI, 2014 Passat TDI
Sounds like your fuel return system is bleeding down. Mine did the same thing, same symptoms and all. The thermo t wasn't sealing correctly, poorly manufactured filter. Replaced the filter and it fixed it right up. Mind you, when the fuel return system leaks, typically it'll let air in when cold, rather than leak fuel. Starts from #1 injector, goes to IP, then fuel filter thermo t. Check all the lines, and replace as necessary. Good luck.
 

turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
Sounds like your fuel return system is bleeding down. Mine did the same thing, same symptoms and all. The thermo t wasn't sealing correctly, poorly manufactured filter. Replaced the filter and it fixed it right up. Mind you, when the fuel return system leaks, typically it'll let air in when cold, rather than leak fuel. Starts from #1 injector, goes to IP, then fuel filter thermo t. Check all the lines, and replace as necessary. Good luck.
I've already bypassed the thermostatic tee and have a filter mount for a standard spin-on filter. All the lines under the hood are new with the exception of the injector return hoses, which are next to be replaced.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
Try moving the IQ to 4-4.5 and see what happens.

The only other thing I notice is your glow plugs are a little high on the ohm scale. They should be in the 0.5-0.7 area, however if they are all about the same and you have no glow plug codes I would leave them alone for now. They shouldn’t affect your idle.
 
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turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
Try moving the IQ to 4-4.5 and see what happens.

The only other thing I notice is your glow plugs are a little high on the ohm scale. They should be in the 0.5-0.7 area, however if they are all about the same and you have no glow plug codes I would leave them alone for now. They shouldn’t affect your idle.
Hammer mod or via VCDS?
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
Hammer mod but if you wanna try it with vcds to see if it makes a difference, I don't think that would hurt

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Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
Car fully warmed up and the hammer mod. I forget you can adjust it with vcds.
 

mr.loops

Veteran Member
Joined
Nov 24, 2010
Location
Kelowna
TDI
2002 jetta, 2003 Bora 1.8T
Car fully warmed up and the hammer mod. I forget you can adjust it with vcds.


If you have a VCDS and can advance or retard the IP pulley, is the hammer mod even necessary?

The only time I can think of needing to do this ( hammer mod) is if your injection timing is waay out of spec




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WildChild80

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Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
If you have a VCDS and can advance or retard the IP pulley, is the hammer mod even necessary?

The only time I can think of needing to do this ( hammer mod) is if your injection timing is waay out of spec




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Hammer mod is for iq, the pulley is for timing

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Nero Morg

Veteran Member
Joined
Oct 19, 2017
Location
OR
TDI
2003 Jetta wagon, 2001 Jetta TDI, 2014 Passat TDI
I've already bypassed the thermostatic tee and have a filter mount for a standard spin-on filter. All the lines under the hood are new with the exception of the injector return hoses, which are next to be replaced.
Another culprit can be the o ring at the quick disconnect fittings next to the firewall. They dry up over time.
 

turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
Slight update. I've changed glow plugs, tried some hot shots fuel additive, and still have the same issue.

My group 13 numbers seems decent
I'm seeing a slight fluctuation at idle but this is pretty close for the most part

1: -0.14
2: 0.28
3: -0.05
4: -0.09

Cylinder 2 is a little higher but I shut it off then fired it back up and cylinder 3 was closer to 2 and the values are lower.

Another thing I've noticed is that at hot idle sometimes idle will get a little rough for a few seconds and will drop to 880 and then it'll come back to 903. Only thing I've noticed is while it does this, IQ drops and then rises back up after it runs smoothly again. There doesn't seem to be any rhyme or reason. It'll just happen randomly at a stop light of something. And it's not very noticeable.

I'm at a loss! I will try bumping IQ but with my hot IQ being around 3.2ish, is that really too far off?
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
No it’s not far off and some cars run fine at that number, but one size (value) doesn’t necessarily fit all. Try bumping it up a bit and see if there is any improvement. You can always return it back to its current value.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Did a quick read of the whole thread, think we may have got side tracked. Seems you've ruled out fueling, glow plugs, injectors (unless they're just wore out). Since it's a newly acquired, I would check timing. Verify engine at TDC, cam slot aligned, IP pin close to hole. Then with VCDS, fine tune so it's in the window. Also with the VCDS check if any of the various temperature sensors are reading whack (check when cold, check when hot).
 

turbotuff

Member
Joined
Oct 22, 2019
Location
Chicago, IL
TDI
03 Jetta Wagon
Did a quick read of the whole thread, think we may have got side tracked. Seems you've ruled out fueling, glow plugs, injectors (unless they're just wore out). Since it's a newly acquired, I would check timing. Verify engine at TDC, cam slot aligned, IP pin close to hole. Then with VCDS, fine tune so it's in the window. Also with the VCDS check if any of the various temperature sensors are reading whack (check when cold, check when hot).
I've checked timing and temp sensors via VCDS and everything is right where it should be. I haven't checked mechanical timing as I don't have the specific tools.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
You can check it without tools, cam is a bit tricky, you have to remove vacuum pump to see align slot. Simply rotate to TDC mark on flywheel and check the other 2. Just don't try to change it without tools.
 
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