VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED

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Tue 15 Nov 2011 12:57
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - Med

Hi, Afternoon.

Alongside the other problems im having with my passat, my mechanic just noticerd today that when he put the car on the lift, started it from cold the cat down to the exhaust manifold were actually red in colour and burning hot, this lasts for about 10 mins then cools back down.

No fault codes are logged for this, any ideas what it could be?

I've had it remapped about 1 month ago.

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Tue 15 Nov 2011 16:16
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - Peter D

Sounds like you have a fueling issue. What are the other problems. Regards Peter

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Thu 17 Nov 2011 16:00
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - martint123
No fault codes are logged for this, any ideas what it could be?

I've had it remapped about 1 month ago.

Looks like you may have answered your own question? Me, I'd get it put back to where it was and see if the problem goes away. If the map is running lean (which makes things run hot) then what it may be doing to your exhaust valves could be expensive.

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Thu 17 Nov 2011 22:58
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - Med

Hi, thanks for your replies.

The only thing i can think it is, may be the other problem im having. the car had a very bad idle, it flutters - going up and down, been trying to find the fault for a few days changed the pressure relief valve and now have ordered new hoses where it looks like a leak may be coming from including new valves.

Since that problem started, my mpg have been extremely bad - usually was getting about 22mpg but now hitting average of 14mpg, big decrease.

I have to see if this is going to fix the air leak, then if it heats up still i will get it demapped as you say or upgrade my air filter and parts to match to the big increase in bhp.

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Thu 17 Nov 2011 19:48
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - hardway

Sounds to me like classic symptoms of a blocked cat.Go back and get him to plug a low pressure gauge into the o2 hole,I'm guessing yours will read more than 5psi,ie,blocked cat/exhaust.and I'm willing to bet a lot of your other "problems" are connected.engines got to breath out!!

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Thu 17 Nov 2011 22:59
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - Med

hi, thanks for your replies.

The CAT is a new one. Ive done about 1,500 miles in it, the previous one blew the flange off.

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Fri 18 Nov 2011 08:40
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - TeeCee

Just 'cos it's a new one does not mean it's OK.

The ceramic matrix is quite fragile and one bit of careless handling between its manufacture and its fitting to your car could have killed it[1].

[1] Disclaimer: No cats were killed or harmed in any way during the writing of this post.

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Fri 18 Nov 2011 08:55
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - injection doc

Running rich can seriously damage a cat ! even just a few miles. Blimey Med you never mentioned before you were getting 14MPG

Do not drive, an air leak can make it run very rich and idle all over the place. If someone had checked the LTFT & STFT they would of seen straight away something was wrong.

No wonder the manifold is lighting up ! Overfuelling, restricted cat and or air leak will all casue the manifold to light up and the ceramics in the cat to melt !

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Fri 18 Nov 2011 09:53
VW Passat 2.0tfsi - Passat, CAT to Exhaust manifold burning RED - Med

thanks for the replies.

Ok, ok - i'll get the CAT checked today sometime.

With the rough idling and air leak it seems to be very common on VW/Audi's, the Pressure relief valve was an obvious thing to be changed but didnt do that much to change but i have ordered new hoses where we think a leak is and 2 new valves for vacuum.

Today, even though the car has been off and on idling i've managed to get back up to 23mpg on average, but it randomly goes up randomly.

I've taken the car so far to 3 Vw dealer, 1 of them i paid diagnostic and the other 2 i refused because they said they will need further time to inspect and find the air leak and that will cost min of £250.00, my local garage sprayed the pipes and we did come across on pipe that made the revs go up again, that pipe i will change tonight as i've ordered it in for today...i hope it will make a difference but i've already taken the car to work today so i'll have to take it easy on the way home.

VW told me its nothing to worry about and i can continue to drive as it seems minor!? also, one VW dealer noticed a crack in my engine over (just the plastic) the guy is telling me i need a new engine cover at £150.00 as its dangerous and can also cause an air leak!?? i told him to sod off but how true is that?

Taking car's out of the mind, its really funny if you think about us talking about an actual cat!! or perhaps its my bad sense of humour :P

Edited by Med on 18/11/2011 at 09:54

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