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Old March 10th, 2012, 08:08   #1
luvsoccer
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Default 2001 Jetta TDI Cold Start Problem

Hi - first post, new owner of used 2001 Jetta TDI sedan. Love the car, averaging 51mpg on first two tanks from long road trip. Only issue is cold starting problem. Car has lots of cranking power, but the first start of each day, with outside temps ranging from 25-45 degrees F, is difficult - takes 5-10 seconds of continuous cranking, and generating lots of smoke, to get it started. My partially-successful work-around has been to cycle the ignition 5-7 times prior to engaging the starter. On most mornings, that seems to shorten the start times (my theory - repeat glow plug warming, even if they aren't at 100%, should help preheat the engine). CEL has never been on.

Mechanics said the coolant temp sensor had erroneous readings so they replaced the sensor during oil change service a couple of days ago, but on starting the following morning I still have the cold start problem. I just checked the glow plugs, including the 3 in the air inlet, and all are 0.5 - 0.9 ohm. A couple of the plugs in the air inlet are around 0.5, the rest are all 0.7-0.9. Might that be a problem? The only other thing I noticed is that the rubber tubing that encases the glow plug wiring supply line (single tube that provides juice to each of the 4 plugs on the block) is cracked in a couple of spots - could that disrupt the current flow? Again, no CEL or codes are present.

I have not had the timing checked - from reading the forum posts I understand that's about the only other thing to check? Appreciate any more guidance anyone can offer. The guy that had the car before me is a mechanic but apparently just lived with the problem - the trunk lid is covered in baked on soot (can see it even though car paint is black) so I suspect this has been acting up for awhile. He said he recently put in new plugs and a glow plug harness along with all the other major maintenance items (timing belt, pumps, etc.).

Thanks in advance for any advice.
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Old March 10th, 2012, 09:08   #2
jettawreck
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There must be hundreds of poor cold start threads, and you have done some (re)searching already. Lots more to do and learn.
"Cold" temps right around 40/45F are sometimes the worst, as the GP really don't cycle (no matter how many times you attempt it) below that temp.
The three extra GPs are in the coolant flange off the head. They don't do anything except help warm coolant a bit faster, mostly an emmissions thing. The automatic versions don't have these.
Timing that is not correct certainly will make a difference. Many have an air leak (most common at the T fitting on fuel filter) either in line somewhere or an IP seal that makes the first start a long cranking affair. Low compression (unlikely), failing battery or worn starter that spins slower than required, despite what many are accustomed to, results in lots of poor cold starts.
Lots of possibilities. Search thru them in this and the MkIV-A4 section of the forum. Like this one:
http://forums.tdiclub.com/forumdispl...aysprune=&f=12
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2004 Cadillac SLS (wife's)
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Old March 10th, 2012, 09:40   #3
luvsoccer
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Default 2001 Jetta TDI Cold Start Problem

Thanks for the corrections. I just noticed there is an air intake tube missing in the air intake "upstream" of the air filter - this missing piece is on the fender side of the battery. The piece that connects to the air filter intake is there - it has a slant cut like a cut green bean on the exposed side, where it is not attached to anything - i.e., there is a 2-3" gap before the next plastic piece that sits right behind the driver side headlight. The slant cut end also has a spring and flap that presumably is actuated somehow to close off most of the incoming air for certain conditions. Might this explain the cold starting problem? Does it normally close off air intake supply when doing a cold start?
Obviously I will have to invest in a repair manual so I can talk more intelligently about the missing tubing and other hardware but I don't plan to do a lot of maintenance myself except for the easy/intermediate, but I would like to narrow the list of possible causes for cold start.
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Old March 10th, 2012, 10:15   #4
jettawreck
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The air tube you're missing would have a screen on the end commonly called the "snow screen". It is often plugged up with bugs, dirt, etc. Some cut it out and there is an upgraded air filter that has a foam top prescreen to it, as later model years did away w/snow screen. The flap is designed to open if the air filter got totall plugged and the incomong air suction would pull that open. has nothing to do w/starting issue you are having.
I personally would get the replacement tube. It pulls air in directly from in front of the grille, instead of out of the warmer engine compartment. Do NOT go for the bogus K & N "cold air intake" style sysems. They are actually inferior and draw air from the engine compartment and the oiled foam element damage the MAF sensor.
I would check the IP timing, the cranking speed and any signs of an air leak first. There is usually a short piece of "clear" fuel line between the IP and the fuel filter. While running if there are much for tiny bubbles going thru or a large bubble after its been parked for several hours, thats a good sign of an air leak.
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2001 Jetta TDI GLS Silver-current driver (salvage)permanently vented-Panzer Plate-Sprint 520s-ScanGauge-CheckTemp III-ZeroStart heater-CAT 2 filter
2003 Jetta GLS Black w/leather (New Project Car) fixer-upper w/broken TB
2004 Cadillac SLS (wife's)
1999 GMC Suburban (It's MN-you need one)
197? Shibura 2cyl diesel 4WD tractor-loader/brushhog (very handy unit)
196? International TD340 Dozer-w/Drott 4-in-1 bucket/back ripper attachment
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Old March 13th, 2012, 19:10   #5
luvsoccer
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Thanks for the wise counsel. I have checked clear fuel line and no signs of bubbles. FYI - I have had the car in two times to local independent VW shop in past 3 days to troubleshoot cold start problem and fix some other minor things and still having cold start problem. I went to pick up car this afternoon after they couldn't duplicate cold-start problem (after I dropped it off there last night). When I attempted to start this afternoon to bring it home - same problem. At least they got to witness it - lots of unburnt fuel smoke and very hard to start. Their comment "it's acting like it's flooded, getting too much fuel." Temperature about 42 degrees F this afternnon and about 32 this morning. The glow plugs were only on for about 1/2 second when I tried to start.

Thus far the coolant temp sensor has been replaced and the glow plugs have checked out OK. The shop has been unable to get a timing reading with their software (APR or ARP?) and asked me if car had been "chipped" for performance mod. I have no idea since I bought it used with no long term records about a week ago.

I still think the plugs aren't staying on long enough to warm it up (my point of reference is personal experience with Mercedes where the plugs stay on 3 seconds or longer) but I am now wondering how the shop is going to ensure timing is right when they can't get a reading...odd.

btw - here's what was replaced shortly before I bought the vehicle:
Glow plug harness
Remanufactured Bosch injection pump
Timing belt, tensioners, rollers
Water pump
Thermostat
Fuel filter
Rebuilt alternator

I also asked them about possibility of flakey glow plug relay and they doubted it - said that would typically generate a CEL code. My intuition is that the plugs aren't staying on long enough.
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Old March 13th, 2012, 19:37   #6
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Longer preglow time will help with starting, but It sounds more like timing is retarded. The recent TB and IP change make me think that is where the problem lies.

Paul
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Old March 13th, 2012, 19:44   #7
luvsoccer
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Thanks - the only odd thing is why did it start just fine for them early this morning? Would 10 degrees cooler (32F vs 42F) be just enough to cause the GPs to stay on longer and 'mask' the timing problem that rears its head at slightly warmer cold-start temperatures?

And regarding their APR software not picking up the timing info, wonder if I will have to go to a shop that uses vag-com...although I thought APR was supposed to be more capable...
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Old March 14th, 2012, 07:44   #8
jettawreck
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Quote:
Originally Posted by luvsoccer View Post
Thanks - the only odd thing is why did it start just fine for them early this morning? Would 10 degrees cooler (32F vs 42F) be just enough to cause the GPs to stay on longer and 'mask' the timing problem that rears its head at slightly warmer cold-start temperatures?

And regarding their APR software not picking up the timing info, wonder if I will have to go to a shop that uses vag-com...although I thought APR was supposed to be more capable...
Yes 10* colder may be enough for the GP cycle to actually come on and help with pre-glow. At aprox 42* they may not really be coming on, even though the indicator lights briefly, as it will at any temp. It comes on as a system test even when GPs don't cycle.

Perhaps the timing is so far retarded that it won't plot on their system. You need to get that issue resolved. VCDS should read it, even if its off the graph. Makes me wonder where/how the rest of the timing belt procedure was done. I would have someone (TDI guru only) look this over for you ASAP. If the job was buggered up it could really be catastrophic if something failed. Its common for "mark and pray" TB jobs to fail and many a decent shops have made mistakes with the tensioner adjustment which prove fatal for the engine over time. Get it looked at would be my advise, even if it means a day trip to the right guy.
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2001 Jetta TDI GLS Silver-current driver (salvage)permanently vented-Panzer Plate-Sprint 520s-ScanGauge-CheckTemp III-ZeroStart heater-CAT 2 filter
2003 Jetta GLS Black w/leather (New Project Car) fixer-upper w/broken TB
2004 Cadillac SLS (wife's)
1999 GMC Suburban (It's MN-you need one)
197? Shibura 2cyl diesel 4WD tractor-loader/brushhog (very handy unit)
196? International TD340 Dozer-w/Drott 4-in-1 bucket/back ripper attachment
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Old March 14th, 2012, 18:10   #9
luvsoccer
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Default Not Giving Up

jettawreck - thank you again for the excellent advice. I just talked to the VW shop foreman at the independent shop (shop gets universally high marks from customers from my research) and they are on the same path now that you outlined this morning - they said they had seen one other TDI awhile ago where the timing was so far off that it wouldn't even register on a graph.
So their game plan tomorrow sounds just like your prescribed note - they are going to pull the covers, re-check the timing belt, (set a cam code or pin???-don't know what that means) then check injector timing. Glad they came to it on their own because I got the speech yesterday about "sometimes you have to take advice from forums with a grain of salt." I attribute that to pride of workmanship - professionals typically don't like to admit that someone else may have the answer or a better approach.

If that doesn't get it resolved I will start searching a wider geographic area for a true Jedi Jetta Master VW TDI guru, or send you an airline ticket to come fix it
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Old March 14th, 2012, 20:03   #10
jettawreck
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Quote:
Originally Posted by luvsoccer View Post
jettawreck - thank you again for the excellent advice. I just talked to the VW shop foreman at the independent shop (shop gets universally high marks from customers from my research) and they are on the same path now that you outlined this morning - they said they had seen one other TDI awhile ago where the timing was so far off that it wouldn't even register on a graph.
So their game plan tomorrow sounds just like your prescribed note - they are going to pull the covers, re-check the timing belt, (set a cam code or pin???-don't know what that means) then check injector timing. Glad they came to it on their own because I got the speech yesterday about "sometimes you have to take advice from forums with a grain of salt." I attribute that to pride of workmanship - professionals typically don't like to admit that someone else may have the answer or a better approach.

If that doesn't get it resolved I will start searching a wider geographic area for a true Jedi Jetta Master VW TDI guru, or send you an airline ticket to come fix it
Most us that have been on here quite a while are very skeptical of dealership TB work, and for good reason(s). It's not a difficult procedure at this point w/o having to mess with the engine mount, etc.
Read thru this:http://pics2.tdiclub.com/pdf/a4timingbelt.pdf
At least you will know if they are blowing smoke or trying to be truthful with their findings and some of the terminology will be familiar.
Good luck there. I'll check back Monday when I get back from Canada ice fishing.
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2001 Jetta TDI GLS Silver-current driver (salvage)permanently vented-Panzer Plate-Sprint 520s-ScanGauge-CheckTemp III-ZeroStart heater-CAT 2 filter
2003 Jetta GLS Black w/leather (New Project Car) fixer-upper w/broken TB
2004 Cadillac SLS (wife's)
1999 GMC Suburban (It's MN-you need one)
197? Shibura 2cyl diesel 4WD tractor-loader/brushhog (very handy unit)
196? International TD340 Dozer-w/Drott 4-in-1 bucket/back ripper attachment
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Old March 25th, 2012, 18:06   #11
luvsoccer
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Default Problem Solved!

Happy to report that the cold starting problem has been solved. Jettawreck - you were right on the money. Independent VW service shop found that even though the timing belt was new, the tensioner was damaged and they believe not installed correctly as they could not properly adjust it. They also found the injection pump timing was so far out of spec that it was not even displaying on scan tool timing table. In addition to replacing the tensioner, they reset the basic timing settings including camshaft and injection pump, then adjusted the injection pump fine setting with a scan tool.
Starts immediately now at all temps whether engine is warm or cold, and seems to run generally a little smoother.
Thanks again for the tips - great site!
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Old March 26th, 2012, 06:21   #12
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Quote:
Originally Posted by luvsoccer View Post
Happy to report that the cold starting problem has been solved. Jettawreck - you were right on the money. Independent VW service shop found that even though the timing belt was new, the tensioner was damaged and they believe not installed correctly as they could not properly adjust it. They also found the injection pump timing was so far out of spec that it was not even displaying on scan tool timing table. In addition to replacing the tensioner, they reset the basic timing settings including camshaft and injection pump, then adjusted the injection pump fine setting with a scan tool.
Starts immediately now at all temps whether engine is warm or cold, and seems to run generally a little smoother.
Thanks again for the tips - great site!
Sounds like a major disaster may have been averted. The tensioner is a major cause of TB failure, especially when its tensioned wrong (often backwards). Your valves and cylinder head could have been trashed and your wallet beat up.
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2001 Jetta TDI GLS Silver-current driver (salvage)permanently vented-Panzer Plate-Sprint 520s-ScanGauge-CheckTemp III-ZeroStart heater-CAT 2 filter
2003 Jetta GLS Black w/leather (New Project Car) fixer-upper w/broken TB
2004 Cadillac SLS (wife's)
1999 GMC Suburban (It's MN-you need one)
197? Shibura 2cyl diesel 4WD tractor-loader/brushhog (very handy unit)
196? International TD340 Dozer-w/Drott 4-in-1 bucket/back ripper attachment
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