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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old October 31st, 2019, 14:50   #1
turbotuff
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Default ALH cold start issue

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!

Last edited by turbotuff; October 31st, 2019 at 16:15.
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Old October 31st, 2019, 15:11   #2
mr.loops
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Default ALH cold start issue

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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Last edited by mr.loops; October 31st, 2019 at 15:19.
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Old October 31st, 2019, 15:17   #3
turbotuff
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Originally Posted by mr.loops View Post
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
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Old October 31st, 2019, 16:28   #4
Fahrvegnugen
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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
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Old October 31st, 2019, 16:39   #5
BobnOH
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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.
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Old October 31st, 2019, 18:48   #6
jmodge
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Have you gone to advanced measuring blocks checked your speciified against actual timing during this period.
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Old October 31st, 2019, 18:53   #7
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As mentioned above, it does start on static timing before the ecu takes over. Maybe bump it around and see what happens
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Old October 31st, 2019, 19:38   #8
WildChild80
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Diesel purge, closed loop system and see if that helps

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Old October 31st, 2019, 22:37   #9
turbotuff
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Originally Posted by Fahrvegnugen View Post
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
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Originally Posted by jmodge View Post
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.
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Diesel purge, closed loop system and see if that helps

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Already done that with no improvement
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Old November 1st, 2019, 00:20   #10
Nero Morg
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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.
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Old November 1st, 2019, 00:23   #11
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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.
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Old November 1st, 2019, 03:36   #12
Tdijarhead
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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.

Last edited by Tdijarhead; November 1st, 2019 at 03:41.
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Old November 1st, 2019, 06:31   #13
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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?
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Old November 1st, 2019, 06:38   #14
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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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Last edited by WildChild80; November 1st, 2019 at 06:41.
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Old November 1st, 2019, 06:41   #15
turbotuff
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Hammer mod

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Hot idle correct?
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