# 03 jetta 2.0 rough cold start



## thedaddy1967 (Mar 4, 2009)

I have a 2003 Jetta with a 2.0/01M that is giving me fits - hopefully someone can help me. I have read through the forums, and checked all of the things that I could find that were related to my car's symptoims, but I can't seem to fix it. The car started to have a very rough idle last winter when the morning temperature got colder. It would start, but it would idle very rough for about 30 seconds, then smooth out and was fine for any starts during the remainder of the day. I read that this problem is often caused by a faulty coolant temperature sensor, so I replaced it with an aftermarket sensor from my local auto parts store. The problem persisted, so I replaced it again with a part from GAP. Still rough, so I finally replaced it with a VW/Audi sensor. There was not a change in the behavior of the car, except now I was getting a CEL. I ran VCDS Lite and it the CEL was from P301 and P302, random multiple engine misfires. I replaced the coil from my local auto parts store, and replaced the plug wires with Bremi wires and the plugs with Bosch double platinum units. The car ran better for two days, then the same rough idle at start up came back, along with the same CEL and codes. I replaced the coil again, this time with no improvement. I got a new code and EPC light for the MAF sensor that said it had a low input, so I cleaned it with sensor-safe cleaner, and when the code wouldn't go away, I replaced it with a rebuilt Bosch unit from FCP Euro. I cleared the codes and started the car. The MAF sensor codes are all gone, but the car still runs rough at start up, and then smooths out after about 30 seconds. The temperatures are warming up, but the rough idle gremlin is still there. The car now idles rough at almost every start, especially if it has been sitting for an hour or two. There has to be something I am missing - what is it? (besides about $300 in parts that haven't made a difference!)

Recap: New coil (2x), new coolant sesnor (2x), new plug wires, new plugs, rebuilt MAF, no obvious vacuum leaks


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## roadsterred (Feb 25, 2010)

Check the Purge Valve and the Gas Cap. The VW emissions system may be the cause of your problem.


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## thedaddy1967 (Mar 4, 2009)

Thank you for the quick reply. I am not really sure how to test the gas cap, but I removed the purge valve, cleaned it and the small filter inside of it, and blew it out with compressed air. I tested it with test leads from a 12v battery, and when the battery was momentarily connected, the solenoid made a clicking sound. I reassembled everything, and this morning it still had a very difficult time getting started. It was about 30 degrees outside, and the car would catch, run for a second, then die. I repeated this "start, die, restart" process 5 or 6 times, and finally it started and stayed running, but it sounded like an old Allis-Chalmers tractor for about 30 seconds - I think it was only running on two cylinders. The CEL came on, and the code was P0301 and P0302. Then, it smoothed out and ran great for the 12 mile drive to work. After work, when it was 50-plus degrees outside, it had the same tough time staying running when I tried to start it. I'm puzzled and still looking for suggestions.


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## rommeldawg (May 25, 2009)

try cleaning and then running the adaption for the throttle body also check compression if it still doesnt improve and the compression is good start looking at fuelling, check fuel pressure check injectors arent leaking down, is fuel pump running/priming when the drivers door is opened


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## thedaddy1967 (Mar 4, 2009)

try cleaning and then running the adaption for the throttle body also check compression if it still doesn't improve and the compression is good start looking at fuelling, check fuel pressure check injectors aren't leaking down, is fuel pump running/priming when the drivers door is opened

I took the TB off yesterday and cleaned it very thoroughly, While doing so, I noticed that the air pipe between the MAF sensor and the TB was very oily. I checked the hose coming from the side of the oil filler neck and found it was completely filled with what can only be described as sludge. The sludge also covered the PCV valve, but I have no idea if it was interfering with its operation. I cleaned all of the sludge out of the pipe and off of the PCV valve and reassembled everything. It dod NOT change the performance of the engine at start-up. I will need to check compression, and I have no real way to run a TB adapt because all I have is the VCDS Lite, and that function is not allowed. I am not sure how to check if the fuel injectors are leaking down, but will search the vortex to see if there are any good threads on this subject. Yes, the fuel pump runs when the door is opened.

I am now experiencing the stumbling idle on every cold start, even if the car has only been sitting for 15 minutes after a long drive. My codes are P030, P0301, and P0302. The random misfires are ALWAYS and have ALWAYS been on cylinder 1 and cylinder 2. Once the car has idles for approximately 20 seconds, it smooths out and runs great. Thanks for the help - KEEP THE IDEAS COMING!


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## thedaddy1967 (Mar 4, 2009)

*what about PCV valve???*

I hope that I still have some followers on this thread! I haven't yet been able to do a throttle body adaptation, but I did clean the TB, and in the process, noticed something that I think is strange about the PCV valve: When the engine is at idle, I can spray TB cleaner into the PCV valve itself, after taking loose the hose from the valve cover, and the engine dies. I guess that I don't understand how this is supposed to work, because to me, that seems like a source for a vacuum leak - a HUGE one. Shouldn't the PCV valve be closed most of the time, so that it isn't sucking air through that hose?


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## thedaddy1967 (Mar 4, 2009)

*What the heck?*

Today, I took the air pipe off of the car, removed the hose from the PCV valve, and sprayed nearly a full can of throttle body cleaner through the PCV valve and the throttle body while the car was NOT running. I used my fingers and a small wooden dowel to prop open the throttle body, and gave it heck with the cleaner, and then let it sit for about an hour. It didn't want to start at first, but once it finally did start, it was soooo smooth. I can't remember when it ran this smooth. I shut it off after about 30 seconds, left it for another hour, cleared the codes, and tried to start it again. Normally, it would be back to its old crappy self, stumbling and throwing codes. NOT THIS TIME! It started right up, idled at about 1,000 RPM for 15 seconds or so, and then slowed down to about 750 RPM. I may have fixed it, or maybe the fix is only temporary - I'm not sure. My question is, what did I do? There must be something dirty or stuck, and I want to make sure that if it needs replacements parts, I have them on-hand. Any ideas?


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## thedaddy1967 (Mar 4, 2009)

*still need help!*



thedaddy1967 said:


> try cleaning and then running the adaption for the throttle body also check compression if it still doesn't improve and the compression is good start looking at fuelling, check fuel pressure check injectors aren't leaking down, is fuel pump running/priming when the drivers door is opened
> 
> I took the TB off yesterday and cleaned it very thoroughly, While doing so, I noticed that the air pipe between the MAF sensor and the TB was very oily. I checked the hose coming from the side of the oil filler neck and found it was completely filled with what can only be described as sludge. The sludge also covered the PCV valve, but I have no idea if it was interfering with its operation. I cleaned all of the sludge out of the pipe and off of the PCV valve and reassembled everything. It dod NOT change the performance of the engine at start-up. I will need to check compression, and I have no real way to run a TB adapt because all I have is the VCDS Lite, and that function is not allowed. I am not sure how to check if the fuel injectors are leaking down, but will search the vortex to see if there are any good threads on this subject. Yes, the fuel pump runs when the door is opened.
> 
> I am now experiencing the stumbling idle on every cold start, even if the car has only been sitting for 15 minutes after a long drive. My codes are P030, P0301, and P0302. The random misfires are ALWAYS and have ALWAYS been on cylinder 1 and cylinder 2. Once the car has idles for approximately 20 seconds, it smooths out and runs great. Thanks for the help - KEEP THE IDEAS COMING!


Well, I am still in need of some help. Here is where I am now: I have access to VCDS Lite, but not full Vag-Com. I have replaced the TB with a rebuilt Bosch unit, and the rough idel and the P0300 (random misfire) and P0301 and P0302 misfire codes are still popping up. I replaced the purge valve solenoid with no improvement, BUT here is a weird thing - I then replaced the spark plugs with the uber-expensive NGK #7968 spark plugs, and the darn thing started right up, and idled perfectly for THREE days. Then, the rough idle at start-up came back. PLEASE HELP ME!!!! It acts like the plugs are fouled and then they get cleared after about 30 seconds of running. Sometimes it even dies a couple of times at start-up. Hot or cold - doesn't matter. I have sprayed ether around the engine bay on the various vacuum hoses and have not noticed a change in RPMs, I can hear the fuel pump prime when the door is opened. I have tried different kinds of gas, have replaced one of the secondary AIR pump hoses that had a crack in it, and I am at my wits-end. Can someone tell me what to try next? I am not opposed to buying a VCDS license, but would need some help on reading the results and looking for specific metering blocks.


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## rommeldawg (May 25, 2009)

were you able to verify fuel pressure at the rail cold? so this is only for the first few seconds cold and then after that the car starts and runs normally? and the tb will eventually adapt itself


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## thedaddy1967 (Mar 4, 2009)

rommeldawg said:


> were you able to verify fuel pressure at the rail cold? so this is only for the first few seconds cold and then after that the car starts and runs normally? and the tb will eventually adapt itself


Thanks for the reply, Rommeldawg! I was hoping to hear from you. I am not able to verify the fuel pressure at the rail - only because I don't know how to do it. My alternative will be to swap fuel pumps with one from a car that is not having problems if you think that is a good idea. I can do the swap in less than 10 minutes. Yes, the rough start is only for the first few seconds, and sometimes it is so bad that the car dies. Once it has started, ran for a few seconds and smoothed out, it can be immediately restarted after a shut-off and it starts great, BUT, if once it sits for a while it is back to the rough starts. The temporary improvement after swapping plugs has really got me baffled. It was two days of driving bliss, and then the rough starts came back. I appreciate your suggestions - thanks again for replying!


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## rommeldawg (May 25, 2009)

try replacing the fuel pump relay first from a jetta that runs normally and when was the last time you replaced the fuel filter?


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## RickZero (Jun 25, 2015)

By any chance, do you have fuel trim numbers? Long and short fuel trims? With these, we can distinguish vacuum leaks or excessive fuels. Once you respond with those, then we can look further into the correct path.

It is also possible that you may have a faulty fuel regulator. Since your issue first began with the car running rough for 30 seconds in the morning, your fuel regulator could have began to slowly go bad. When the diaphragm inside these things go bad, they typically crack and higher pressure flows. They can also fail by sticking and just barely opening. The injectors can also be an issue, but once you can post the fuel trims, we can see if you are have an air issue or a fuel one.

Side note: When you replaced your plugs, you did not use that "non-electrical grease" correct? I couldn't tell you how many times I have ran into the issue where that grease is the root problem to the electric systems.


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## thedaddy1967 (Mar 4, 2009)

*answers to questions*



RickZero said:


> By any chance, do you have fuel trim numbers? Long and short fuel trims? With these, we can distinguish vacuum leaks or excessive fuels. Once you respond with those, then we can look further into the correct path.
> 
> It is also possible that you may have a faulty fuel regulator. Since your issue first began with the car running rough for 30 seconds in the morning, your fuel regulator could have began to slowly go bad. When the diaphragm inside these things go bad, they typically crack and higher pressure flows. They can also fail by sticking and just barely opening. The injectors can also be an issue, but once you can post the fuel trims, we can see if you are have an air issue or a fuel one.
> 
> Side note: When you replaced your plugs, you did not use that "non-electrical grease" correct? I couldn't tell you how many times I have ran into the issue where that grease is the root problem to the electric systems.


RickZero, thank you for the suggestions. I only have VCDS Lite so I don't think I can get the fuel trim numbers for you. I have a spare fuel pressure regulator that I can try. I have ruined a set of plug wires when I tried to remove them at a scheduled plug change and they were stuck to the plugs, so, yes, I used the dielectric grease on both ends of the spark plug wires - both where they attach to the coil and where they attach to the plugs. Rommeldawg, if you are checking in on this post, today I replaced the fuel filter and the rough start was still there. I also switched out the #409 relay and there was no improvement. I have noticed that once the car runs for 30 seconds or so and a second start is done, it does not idle rough, and I do not get any new codes.


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## rommeldawg (May 25, 2009)

yes fpr is worth looking at... fuel pressure test would verify good or bad and show residual pressure maintained after shut down which is useful. you can also test for volume/flow but the lines themselves are very hard to get off an old car without destroying. so dropping in a fpr from a known good running car would be quick. as for fuel trim and vacuum leaks it is possible but you were not getting a lean code and these engines typically were not prone to the vacuum leak issues like the 1.8t, there are far less things to leak. two most common were brake booster line to intake and fpr vacuum line.


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## thedaddy1967 (Mar 4, 2009)

rommeldawg said:


> yes fpr is worth looking at... fuel pressure test would verify good or bad and show residual pressure maintained after shut down which is useful. you can also test for volume/flow but the lines themselves are very hard to get off an old car without destroying. so dropping in a fpr from a known good running car would be quick. as for fuel trim and vacuum leaks it is possible but you were not getting a lean code and these engines typically were not prone to the vacuum leak issues like the 1.8t, there are far less things to leak. two most common were brake booster line to intake and fpr vacuum line.


I swapped out the FPR and did not experience any improvement. Do you suggest that I purchase a version of VCDS from Ross-Tech so I can perform better diagnostics? I sprayed ether around the hoses again, and no change in idle occurred, so I am doubtful of a vacuum leak. I am really frustrated that the car runs like crap for about 30 seconds, and then behaves. It is almost like some sensor needs warmed up or some excess fuel needs burned off right at the beginning of startup. It has a rough start EVERY time now - even when the engine is warm. Its driving me nuts!


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## RickZero (Jun 25, 2015)

I just back read the entire post to see everything you have done and what not. There are 2 things that I would recommend doing next.

1. It is very possible that one of your injectors (specifically 1 & 2) may not be shutting completely when you power off your car. Fuel can still be bypassing into cylinder 1 & 2. Hence, why the car acts funny for the first 30 seconds. It needs a few seconds to burn the excessive gas that is already sitting in the cylinder. When you start your car, it probably sounds like crap right it turns on. If you can get your hands on a fuel pressure tester, I recommend to test the pressurized fuel line maybe 2-4 hours after the car has been sitting. You should still have , if I remember correctly, over 30 PSI remaining. If you have less, then that means the fuel is going somewhere hen the car is off. 

2. You should really find someone with VCDS to adapt your throttle body. The only way to adapt your throttle body is by using VCDS. When you turn your key to the on position, your throttle body will make a noise because its doing the initial self test. Many people believe that it is doing and actual adaption. When the car is on, the throttle body will adjust itself (the idle control is built in) to compensate for excessive or lean amount of fuel. If your throttle body is not adapted, then the control will obviously adjust itself to correct idle speed, but if you adapt it, it will not have to work as long to adjust. When your turn your car on right now, you probably see your RPM gauges bounce up and down slightly for about 1 minutes or so. Overall, this adaption is not the reason for your car acting funny for the first 30 seconds, but it is not something that you should let go for a long time.

Note: If you don't want to spend the money for VCDS, then you should try posting in the regional section for your area and see if someone has a one.


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## thedaddy1967 (Mar 4, 2009)

RickZero said:


> I just back read the entire post to see everything you have done and what not. There are 2 things that I would recommend doing next.
> 
> 1. It is very possible that one of your injectors (specifically 1 & 2) may not be shutting completely when you power off your car. Fuel can still be bypassing into cylinder 1 & 2. Hence, why the car acts funny for the first 30 seconds. It needs a few seconds to burn the excessive gas that is already sitting in the cylinder. When you start your car, it probably sounds like crap right it turns on. If you can get your hands on a fuel pressure tester, I recommend to test the pressurized fuel line maybe 2-4 hours after the car has been sitting. You should still have , if I remember correctly, over 30 PSI remaining. If you have less, then that means the fuel is going somewhere hen the car is off.
> 
> ...


RickZero, you may be onto something here! I ordered a brand new Bosch fuel pressure regulator last week, just to eliminate the possibility that the one that I was trying from a donor car that I have was faulty. I drove the car all day today off and on, and parked it at home at 2:30 this afternoon. After dinner 5 hours later, I went out to the car to change the FPR, and when I pulled the retainer and lifted it out of the socket, THERE WAS NO RESIDUAL PRESSURE! It sounds like the injectors could be due for replacing. Can you confirm this based on what I have described?


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## rommeldawg (May 25, 2009)

well there is a check valve in the pump as well that should maintain some residual fuel pressure. you would need to either pull the injector rail and test them or you could pull the plugs and look into the cylinders. i take it the new fpr didnt help?


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## thedaddy1967 (Mar 4, 2009)

rommeldawg said:


> well there is a check valve in the pump as well that should maintain some residual fuel pressure. you would need to either pull the injector rail and test them or you could pull the plugs and look into the cylinders. i take it the new fpr didnt help?


The new FPR did not work. I have no real way to test them, so I guess that I will purchase rebuilt ones and see if that does the trick. Any other suggestions?


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## rommeldawg (May 25, 2009)

well the test is crude but you would have the injectors pulled out of the intake but still attached to the rail and crank the car with the coil unplugged checking the spray pattern and that when they shut-off they do not continue to leak beyond just a drip or so. it could though just as likely be the fuel pump itself


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## thedaddy1967 (Mar 4, 2009)

rommeldawg said:


> well the test is crude but you would have the injectors pulled out of the intake but still attached to the rail and crank the car with the coil unplugged checking the spray pattern and that when they shut-off they do not continue to leak beyond just a drip or so. it could though just as likely be the fuel pump itself


Thanks for the suggestion, Rommeldawg. That is kind of the way that I was going to test the injectors. As far as the fuel pump is concerned, I can understand that losing pressure after several hours could mean a leaky injector (or two) or a leaky check valve in the fuel pump, but I don't understand how the leaky check valve would produce my symptoms. I can hear the fuel pump prime when I open the door, so would that bring the pressure back up in the fuel system prior to starting? I may as well replace the injectors while I have it all torn apart anyway - I have replaced nearly every other component on this engine in the process of chasing this demon!


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## rommeldawg (May 25, 2009)

no you hear the fuel pump run, but insufficient pressure or if the lines have bled back to where there is air in them a single key cycle will not compensate for this


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## thedaddy1967 (Mar 4, 2009)

rommeldawg said:


> no you hear the fuel pump run, but insufficient pressure or if the lines have bled back to where there is air in them a single key cycle will not compensate for this


Thank you for getting back to me and giving me a little education on this - I will try both the injector test and maybe another fuel pump from another car. That is a simple change!


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## thedaddy1967 (Mar 4, 2009)

thedaddy1967 said:


> Thank you for getting back to me and giving me a little education on this - I will try both the injector test and maybe another fuel pump from another car. That is a simple change!


So, last night I had an idea - swap the injectors from the cylinders that are throwing the misfire codes (1 and 2) with the injectors that are not throwing the codes (3 and 4). My thinking was that if the problem is with the injectors, the codes would follow them to cylinders 3 and 4. At least, that's what made sense to me! I did the swap, cleared the codes, and restarted the car. Within three starts and stops, the codes came back, and they are still with cylinder 1 and 2. I don't think its the injectors. Any thoughts on what to try next?


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## rommeldawg (May 25, 2009)

have you checked compression, compression fuel spark... one of them is usually the problem.


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## thedaddy1967 (Mar 4, 2009)

I'm not sure who is still following this thread - but just in case...I spent last Saturday cleaning the battery terminals (they were already pretty clean and coated in dielectric grease to prevent corrosion), and I changed the broken fuel injection terminals (I broke one of the clips trying to remove the connector, and the rest were broken by the PO). I also noticed that the connector to the coil was not "clicking" into place because it had a broken retaining clip, and I cleaned the connections for the ground wires under the battery box that connect the battery to the frame. Since doing these things, the car has started every time with no misfires and has been running like a dream. Thanks for replying and keeping my in the loop with your ideas.


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## rommeldawg (May 25, 2009)

good deal... i like your persistence and thanks for keeping the thread updated


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## thedaddy1967 (Mar 4, 2009)

*I'm back!*

I appreciate all of the help and suggestions - I have been driving the car and putting up with the misfire code for a while now - it keeps reappearing. However, I am nearly 100% convinced the problem is not with the coil, wires, or plugs, as these are all new. The other day, the car wouldn't start,. and had an 0322 code, so I needed to replace the crankcase speed sensor. During that maintenance and oil change, I noticed that there is serious positive air pressure coming out of the top of the valve cover when the filler cap is removed, and the bottom of the filler cap and the neck of the valve cover have a tan "sludge" on them. The sludge doesn't surprise me - we have had some crazy weather in Indiana and moisture in the air may be causing some condensation in the crankcase. What concerns me is the volume and pressure of air that is coming out of the hole with the cap removed. I am wondering if some of this "sludge" could be drawn into the engine during startup and could be the cause of the rough idle. The car only idles rough for about 15-20 seconds, and then smooths out - almost like the plugs get fouled, then the clear themselves once they get warmed up for a few seconds. The tube connecting the intake tube/PCV valve to the valve cover was also FULL of the sludge, as was the PCV valve itself. I grabbed an intake tube from a local salvage yard, but am having the same problem with it. Any thoughts?


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## RickZero (Jun 25, 2015)

How is your coolant level? Do you have to add coolant every so often? What about oil levels? Do you add oil after a set amount of miles? Have you been able to check the compression on cylinder 1 and 2? Could you possibly get a picture of all 4 spark plugs and post them on here? 

It sounds like your issue is within the head or the block.

-If the issue is the block, then your piston rings would be worn causing blowby and allowing oil to enter the cylinder.

-If the issue is the head, then you can have bad valve stems allowing oil to slowly seep down into the chamber. You may also have a crack in the head between the 2 cylinders and/or between the oil ports. This will, of course, cause excessive pressure to be pushed out when your remove the oil cap.

-If the head gasket it bad then you can also have air, oil, and water mixing back and forth causing white milky looking oil into your engine.

Highly recommend doing 2 different test and compare number:

--Leak down test
--Compression test


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## thedaddy1967 (Mar 4, 2009)

*updates*

RickZero, thanks for the reply - yes, I need to add coolant every so often. At first, I thought it was because of a slow leak around a hose or something. Now i suspect it is much more serious! The leak is very slow, because I only add coolant about every 1,000 miles or so. Also, I need to add about a quart of oil - nearly at the same 1,000 mile interval. I have a slow drip from the drain plug that I can't seem to stop, which contributes to the need for oil. I did a compression check today, and here are the numbers: cylinder #1 - 210, cylinder #2 = 195, cylinder #3 = 190, cylinder #4 = 210. I have no idea how to post pictures of the spark plugs!


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## thedaddy1967 (Mar 4, 2009)

*Still at it!*

I'm really not sure who is still reading this thread - hopefully Rommeldawg and RickZero! I finally found the source of one of the slow coolant leaks - I had a heater hose split while I was driving the wagon to work the other day. I noticed that the inside of the hose was really badly eroded - and when I added water back to the expansion tank, I noticed that there was a lot of black rubber granules in the bottom of the tank. It makes me suspect that I need to replace a few more hoses! I have been thinking about the compression numbers, and have paid super-close attention to the exhaust at startup. I have no smoke in the exhaust - blue or white. I also changed the oil a few days ago, and the oil is not milky, other than the small amount of sludge that has been just inside of the fill cap. Even with the new hose, I am still losing coolant somewhere, but I'm not sure where. I am not convinced that the leak is in the head or head gasket. I have to say that the car has been starting and running much better since the hose was replaced, but I am not sure how one would have anything to do with the other.


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## Jzunrod (8 mo ago)

Hey, I am having same issue with a 2004 Jetta 2.0 Aut; did you solve it? I have to cold start mine using engine starter can every day.


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## ReidCleland (7 mo ago)

Jzunrod said:


> Hey, I am having same issue with a 2004 Jetta 2.0 Aut; did you solve it? I have to cold start mine using engine starter can every day.


I am also having the same issue, if youve figured it out lmk...


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