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Discussion Starter #1
I have an issue with my 2004 Passat 1.8t. The car usually shakes or vibrates roughly on start up and at times the engine light will flash. It usually stops when I start driving but the odd time I do have to shut it off and turn it back on.

I replaced my spark plugs but it still happens. Also I’ve been told I need to replace my thermostat but I dont think it’s related to the issue.

I do have 2 engine codes:
05241
08577

Im thinking I should changing the coils next.
 

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That problem is NOT caused by the thermostat.
I suggest you check the CTS in the coolant flange at the back of the head.
Check or replace the vac lines and all PCV system.
 

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Has the plenum, where the battery is located, been flooded?
I had the same code when I bought the car. Found out that the brake booster was submerged in water due to clogged up drain holes there.


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Discussion Starter #5

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That problem is NOT caused by the thermostat.
I suggest you check the CTS in the coolant flange at the back of the head.
Check or replace the vac lines and all PCV system.
thanks! So start with replacing the coolant temperature sensor and see if that fixes the issue? And if not then the vac lines and all PCV system?
 

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Has the plenum, where the battery is located, been flooded?
I had the same code when I bought the car. Found out that the brake booster was submerged in water due to clogged up drain holes there.


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Not sure. Any resources on how to check it myself or is that something better to get a mechanic to do?
 

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P2181 can sometimes be a thermostat, but in this case with your symptoms, the CTS would be the first one to look at.

Axenstar's recco refers to the area under the plastic cover at the firewall where the battery is located. The drains in there can clog and water can fill that area, messing with wiring or brake components.

The brake boost vacuum code could be a split or separated suction jet pump assembly. If original to the car, it can crack open at a seam causing a vac leak and that is connected directly to the booster via a curved hard plastic pipe into the firewall. They revised that part later on. 058 133 753 D.

Amazon/eBay has assemblies like this.
 
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If the misfires are on both warm and cold starts, you probably have a vacuum leak in the power brake system. It will often throw the P1479/005241 code even if the pump is working. It just notes that the pump is not producing enough vacuum and assumes it's the pump.
I've found the large cloth covered line under the coolant tank leaking where it attaches to the hard metal line that continues to the vacuum reservoir. The cloth hides the break in the line, but this leak causes the car to deplete the vacuum reservoir, making the car replenish it upon startup.
As for the P2181, I find it is the thermostat in most cases.
 
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If the misfires are on both warm and cold starts, you probably have a vacuum leak in the power brake system. It will often throw the P1479/005241 code even if the pump is working. It just notes that the pump is not producing enough vacuum and assumes it's the pump.
I've found the large cloth covered line under the coolant tank leaking where it attaches to the hard metal line that continues to the vacuum reservoir. The cloth hides the break in the line, but this leak causes the car to deplete the vacuum reservoir, making the car replenish it upon startup.
As for the P2181, I find it is the thermostat in most cases.
Shouldn’t the auxiliary booster pump be kicking in constantly to compensate the lack of brake pressure boost?



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Feel free to read this article if you have time as it can give you the answer and solution to your problem.

 

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Shouldn’t the auxiliary booster pump be kicking in constantly to compensate the lack of brake pressure boost?



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Yes, it should, but it can't overcome the leak and a depleted reservoir on startup. While running, the engine will do a good job of producing vacuum even with a leak.
 
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Feel free to read this article if you have time as it can give you the answer and solution to your problem.

Thanks will do.
 

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If the misfires are on both warm and cold starts, you probably have a vacuum leak in the power brake system. It will often throw the P1479/005241 code even if the pump is working. It just notes that the pump is not producing enough vacuum and assumes it's the pump.
I've found the large cloth covered line under the coolant tank leaking where it attaches to the hard metal line that continues to the vacuum reservoir. The cloth hides the break in the line, but this leak causes the car to deplete the vacuum reservoir, making the car replenish it upon startup.
As for the P2181, I find it is the thermostat in most cases.
its mainly on cold start ups, usually doesn’t happen on hot start ups from what I recall
 

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Forget about the thermostat for now, a faulty thermostat can't cause rough running on a cold startup.
 

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Thanks. I’m thinking of starting off with replacing the CTS and seeing how that goes.
 

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You can check the CTS with VCDS, by checking the 2 temps reported to the gauge and the ECU.
If the CTS is OK, check for a leak in the vac system and the PCV system.
 
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