Changed battery / found disconnected intake hose

JSH1

Member
Joined
Jul 14, 2018
Location
PDX
TDI
2014 JSW TDI DSG
I pulled the battery to replace it and found an intake hose with an ID of about 1.5 inches disconnected.
What is this hose for and it is possible it was disconnected as part of the emissions Fix or the charge cooler icing problem?

https://photos.app.goo.gl/EYqmp2VmpMVhHSjZA



This is a 2014 Jetta Sportwagen TDI DSG. CPO car with an appointment next week for some issues.

Background

For about 6 months the car occassionally will misfire and bog under acceleration. It is random and can happen a couple times a day or go a month without happening. I hit the throttle to go, the car bogs and looses power, and then clears in about 1 second and takes off.

Last Sunday I had what I thought was an iced charged air cooler. The car started fine at 25F. I drove 30-40 minutes to the snow park to ski. I came back 4 hours latter and the car started then immediately died. (Temp 39F) The next crank got about a 1/2 turn. The 3rd attempt nothing. 4th attempt it cranked fast for a about 2 seconds and started but died again. 5th attempt nothing. I jump started the car and it cranked, ran rough for about 30 seconds and then idled normally. I drove to an auto parts store for a battery capacity test and they said the battery was fine. The lights on the dash were fine, not dim, no warning lights. The next morning the car started again at 22F and it has started and ran find all week until..

Last night (5 days later) the car cranked slow coming home from the store but started. Got home and the voltmeter says 12.4V. Put the battery on a charger and it says it charged to 12.8v but the next morning it is down to 11V and the lights on the dash flicker and lots of buzzers. So the battery is dead, I pull it out and find mystery hose.

So could this hose be causing by misfire under acceleration? For my trip to the dealer should I leave it disconnected tell them about it. Or should I connect the hose and drive the car for a bit to see if it fixes the problem? The car is CPO but they charge a $155 diagnostic fee if they can't replicate a problem and don't fix anything.
 
Last edited:

soot1

Veteran Member
Joined
Nov 6, 2009
Location
Houston, TX
TDI
Currently none. Formerly: 2010 VW Jetta TDI 6M, 1993 Dodge Ram W250 Cummins 5M 4WD, 1990 VW Jetta Diesel 5M, 1986 VW Jetta Diesel 5M, 1980 VW Uabbit Diesel 4M. Currently driving 2018 Toyota 4Runner SR5 4WD.
That hose is there to bring warm air from behind the engine to the intake, and its purpose is to shorten the time it takes the engine to warm up in cold weather. Therefore, I seriously doubt it is the cause of the problems you are seeing.
 

jhintontdi

Veteran Member
Joined
Jan 15, 2004
Location
PDX
TDI
2014 JSW TDI DSG
That hose is there to bring warm air from behind the engine to the intake, and its purpose is to shorten the time it takes the engine to warm up in cold weather. Therefore, I seriously doubt it is the cause of the problems you are seeing.

Thanks for the reply. Without the warm air from behind the engine would the charge air cooler be more likely to freeze?

While it is likely that my failure to start was due to the battery I still find it really odd that the car would not turn over at all and then the next attempt crank like normal. I have never had a dead battery recover and work for a week after being so dead it would not turn the engine at all.
 

soot1

Veteran Member
Joined
Nov 6, 2009
Location
Houston, TX
TDI
Currently none. Formerly: 2010 VW Jetta TDI 6M, 1993 Dodge Ram W250 Cummins 5M 4WD, 1990 VW Jetta Diesel 5M, 1986 VW Jetta Diesel 5M, 1980 VW Uabbit Diesel 4M. Currently driving 2018 Toyota 4Runner SR5 4WD.
Thanks for the reply. Without the warm air from behind the engine would the charge air cooler be more likely to freeze?
While it is likely that my failure to start was due to the battery I still find it really odd that the car would not turn over at all and then the next attempt crank like normal. I have never had a dead battery recover and work for a week after being so dead it would not turn the engine at all.
If you have enough water in the intercooler hose and the hose is exposed to freezing temperatures, it will completely choke off your air passage into the engine, and you will not be able to start the engine, whether or not the warm air hose is connected. The symptoms you described earlier clearly indicate you have a dead battery. When a battery is about to release its ghost, you can see some really strange behavior, including miraculously coming back to life for a few moments, only to go really dead for good the next minute. Don't spend too much of your time on this, get a new battery, drain the water from the intercooler outlet hose, and move on.
 

jhintontdi

Veteran Member
Joined
Jan 15, 2004
Location
PDX
TDI
2014 JSW TDI DSG
Well the car has a new battery and still runs rough. It is under warranty so the dealer can sort it out.

Thanks for the replies.
 
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