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Discussion Starter · #1 ·
Hello,

Since, last Friday, I had to spend more than a minute to start my 2003 VW Passat Wagon engine. I thought it would be related to my 5-year-old battery so I replaced it yesterday. Today in the morning I tried to start and I still have the issue. It did not start for a minute and one time I thought it started but it went down. But the interesting part is that I can start the engine again and again without issue after the first hard start and running for 5 minutes. I never had this kind of experience and I am wondering if you have any similar experience.

Side note, I added 1 quart of engine oil(5W-40) to top up but it is still low. I just want to confirm that you add engine oil through the bubbled lid right? Before I add another engine oil, I was going to check with my mechanic if there is any issue with this engine start issue. Do you think low engine oil can create an issue with starting the engine in the morning?

Thank you for sharing all of your insight and advice.

bigevent.
 

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Yes, you've identified the oil fill cap. It should have an oil can image on it.

No, low engine oil has zero influence on starting the engine.

Your starting problem may be a defective coolant temperature sensor, fairly common. Air leaks can also have that effect.
 

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Discussion Starter · #3 ·
Hi ylwagon, Thank you for your comment. What I am not fully understanding is why it works fine after the first difficult start. Does defective coolant temperature sensor or air leak create the same issue whenever I start the engine? Do I ruin the car when I am trying to start the engine in the morning with multiple engine ignition trials and keeping the key at the ignition position for a long time?
thank you.
bigevent
 

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Once the engine has been run 5 minutes it is warmed up a bit. If the coolant temperature sensor (CTS) failed and indicated that the engine was hot all the time it would start normally when hot but wouldn't get enough fuel when cold.

If you try to re-start it immediately after it starts but before it warms up does it start normally?
 

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Discussion Starter · #6 ·
Hi Lowegian,

I tried what you told me. It took me about three times trial of 5-10 second of keeping the key at ignition position. After I was able to start the engine( sound was not that good and it sounds like it is about to stop), I turn it off and started again. Second time was also not easy but I could start with about 5 second ignition position. I turned it off and tried again. It was easier and got better. I turned off the engine and tried again. Fourth time it was more or less normal. I drove 20 min and parked for about one hour. When I started the engine again it was normal.

Does it tell you any clue on this issue?

Thank you.

Bigevent
 

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Sounds exactly how mine was acting last time the CTS failed. Failing VCDS or another VAG-compatible scanner handy, I'd just go ahead and replace it. The part isn't that expensive or that awful to replace. (NB: get at least one extra sensor retaining clip).
 

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Here's a video of the process.
I don't have a V6 but I assume this is how to do the job on your car.

It's usually recommended to get an OEM version of this part since cheaper varieties can fail. If your OBD setup can read the temperature read by the engine, that is what you want to see. There are actually 2 separate sensors in the CTS. One is used to display the coolant temperature on the dash and a completely separate one is used by the engine management system to determine how warm the engine is. It's not uncommon for one to fail while the other works.
 

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Discussion Starter · #10 ·
Hi lowegian, Thank you for the video. So CTS that scotts13 mentioned means "Coolant Temperature Sensor". Thank you for the lesson and I will let my mechanic know to see the CTS error. My mechanic does not normally choose OEM version for the auto parts but I will let him know that I want the OEM CTS if that is the issue.

So the engine start issue started last Friday morning. Do you have any clue why that happened? Two weeks ago was even colder but I did not have any issue with starting the engine in the morning. I would like to know what I should do to avoid failing the CTS in the future.

Thank you for all your lessons.

bigevent.
 

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You don’t need to purchase an OEM temp sensor - think about it… VW does NOT make the parts that are in your car. A VW dealer will charge you $220 for a temp sensor where the same brand name is available at rockauto.com for $30. You can get cheaper ones than that too. And the way that guy in video is doing it, you better have very small hands to fit down the back that way. If your hands are like mine, you’ll have better luck just taking off the ribbed tube between the air box and the snorkle, and remove that back snorkle to the throttle body. Never mind the air box cover; it’s a distraction. If your sensor was never replaced in a long time, you’ll need a bit of prying force to break it free as it sits in a seat that might be gunked up with old coolant and whatever ridiculous coolant additives someone else may have added - like stop leak… But before you do, make sure the engine is dead cold or you’ll have a fountain of coolant.. (don’t ask how I know this) so you may want to also drop the coolant level just a tad with a vacuum pump… (it’s hard to get to the rad drain without removing the bumper cover)
 

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I wouldn't bother with lowering the coolant level. Do this job with the engine cooled off, and leave the coolant filler cap on the reservoir. The coolant loss should be minimal. And don't miss scotts13's comment about an extra retaining clip. These get lost when they spring off, unless you tie a long piece of dental floss to them first.
 

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Discussion Starter · #13 · (Edited)
Hi Rob,Achmann and ylwagon,

Thank you for sharing your experience. I will see what my mechanic says when I see him tomorrow. I wish I could try by myself but I don't have the right experience and tools to do this job. From your story, it sounds like I would need to pay some money for this fix.

FYI, I filmed how I started the engine today which you can check from the link below.


It was not too cold since it rained so it was not too bad to start the engine. But the engine started without any excitement and it stopped by itself after it started first times. I noticed that the sound of the engine was not recorded clearly but you will hear it when you raise the volume. Sorry for the dinging sound. I thought it can be a good reference for the future.

Thank you.

bigevent
 

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Discussion Starter · #14 ·
Hi all,

Today I checked with my mechanic and he said that his scanner indicates that my Coolant Temperature Sensor is working. He told me his experience, the engine start issue in the morning can happen from a bad fuel filter. He gave me an instruction that tomorrow morning, turn the key on and keep it for 3 seconds and turn it off. And do the same five times before I actually crank the engine. According to him, if this helps to start the engine, the current issue is definitely from the bad fuel filter. I am wondering if you had this kind of issue from a bad fuel filter.

FYI, today's temperature was at around 32F so took me 2 minutes to start the engine. For the record, I am leaving the recording file below.


I will keep you updated. Thanks.

bigevent
 

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Hi,
I am really interested to know how you get on. Something similar has just started happening with my 2011 2.0ltr bluemotion Passat.
Any help would be greatly received. Will try the key thing tomorrow when cold. By turning on for 5 secs off etc without starting to see if helps.
but it only does this on first start in the am. Doesn’t do it later in the day. Left it for 8 hours today after first bad start and was fine. Will try and add video if I can work it out.

vikki
 

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Hi,
I am really interested to know how you get on. Something similar has just started happening with my 2011 2.0ltr bluemotion Passat.
Any help would be greatly received. Will try the key thing tomorrow when cold. By turning on for 5 secs off etc without starting to see if helps.
but it only does this on first start in the am. Doesn’t do it later in the day. Left it for 8 hours today after first bad start and was fine. Will try and add video if I can work it out.

vikki
This is a totally different engine and generation of Passat to yours. I would suggest that any further posts on the subject for your car be made in the B6 forum in a new thread. Asking advice in this thread will only derail the current members' conversation and confuse things.
 

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Today I checked with my mechanic and he said that his scanner indicates that my Coolant Temperature Sensor is working. He told me his experience, the engine start issue in the morning can happen from a bad fuel filter.
If the CTS is truly working correctly, then an air leak or low fuel pressure are possibilities. But I disagree about the fuel filter. A dirty fuel filter acts similarly to a resistor in series with an electrical load: When supplying current to a very small light bulb, the resistor may be insignificant. But use a large bulb instead, the Voltage may be lowered significantly by the same resistor.
In the case of your starting issue, consider that the lowest demand for fuel flow is at cranking RPM, while the highest demand for fuel flow is at full-throttle, max RPM. So a filter clogged enough to prevent the engine from starting, would be too clogged for driving.
 

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Well, I had issue on cold start when I forgot to connect the pvc tube to the intake manifold- the one that goes to the brake booster, etc. But it sounded crazy bad if it even got started. So my issue was air leak in the worst way. So air leak sounds decent. But my CTS didn’t throw codes before I replaced it - neither did the temp switch for the rad fan. Now after replacing both, things work
 

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Discussion Starter · #19 ·
Thank you for sharing your experience. As you mentioned, changing fuel filter did not work. It took me 3-4 min to start today as well. As always, it seems to be normal after the first difficult start of the engine.

Here is more detailed description. I tried not to step on the gas pedal when it starts today. It kept stopping for a couple of times when first started. When engine first started, the condition was not very stable and the car was shaking with the unstable engine sound. When the engine finally kept running after 3-4 minutes of try, I kept it on for about 5 minutes, then everything seems to be normal and I can start engine easily from that point.

One thing I am worried is if I am making the condition worse by spending 4-5 minutes of engine starting and cranking.

My mechanic kept on saying that CTS should turn on engine light if it is an issue. I mentioned about air leak and low fuel pressure but the mechanic was not interested in checking that.

I opened and checked the engine air filter and it seems to be fine. I will keep you updated and thank you again for all your advices.

bigevent
 

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Discussion Starter · #20 ·
Sounds exactly how mine was acting last time the CTS failed. Failing VCDS or another VAG-compatible scanner handy, I'd just go ahead and replace it. The part isn't that expensive or that awful to replace. (NB: get at least one extra sensor retaining clip).
Hi scott13,

When you had the similar issue, was it okay after you started the engine first time in the morning? I am trying to understand why my car works fine the whole day after the difficult start once in the morning.
 
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