Question - TDI in limp mode for about 40 seconds?

GoneDiesel

Veteran Member
Joined
Jun 2, 2000
Location
USA
Today may TDI went into limp mode for about 40 seconds and then snapped out of it. No engine light thrown. I didn't have my laptop in the trunk to check. After I got home there were no codes. What I did notice before this happened I was showing my friend the engine bay and notice a very large air bubble in the fuel line. When I got home the air bubble was not there. Later in the day after sitting a couple of hours a smaller air bubble was present. I have checked for any leaks but can't really see anything suspicious. When a TDI goes into limp mode because the ECU is putting it in limp mode for what ever reason, wouldn't it throw a code or cause engine light to come on? Could the airbuble be the culpret? I have driven it several time today without it happening again. Tomorrow I will check for air bubbles after sitting all night.
 

DEZLBOY

Veteran Member
Joined
Feb 19, 1999
Location
Arlington VA
TDI
2000 Golf GLS, Candy White
I've read messages that air bubbles in fuel line is okay. Limp mode means would only go real slow....or did you lose all power?
 

GoneDiesel

Veteran Member
Joined
Jun 2, 2000
Location
USA
DZELBOY, it did loose power. I had it floored and it would only do about 35mph in 4th. I let off of it and let it idle several times and then it finally powered back up. I see different size bubbles too and I don't think they really bother much. The bubble I had that day was about 3-4 inches long in the fuel line. Then when I got home there was none. Later that day there was a small one. I didn't have my laptop to run diagnostics. I just bought a Sony VIAO slimcomputer to place in my trunk just for this type of ordeal.
 

dsljay

Veteran Member
Joined
Sep 15, 2000
Location
Allentown, Pa. USA
Gone diesel- We had a similar problem with are 96 Passat. On three or four occassions the motor went into limp mode and did not respond to the accelator peddle. This happened at low speed. After the 2nd time I replaced the fuel filter, but it happened again. No check engine light. The bad news is that I never found the problem, the good new is that it hasn't happen in about 40K miles.( I guess it is fixed)Since the accelator is a "drive by wire", I'm guessing that the problem was in a sensor. Good luck,
 

golfstream

Top Post Dawg
Joined
Jan 10, 2001
Location
Balmer, Hon
TDI
Golf, 2000, Black
Don't think it's the air bubble. Air bubbles are usually visible in my clear fuel line and vary in size also. Sometimes I look and they are virtually non existent. Other times there is a large one. I have also noticed (I think) that when I first stop the engine there may be a small air bubble that may get larger the longer the car sits. Also, there seems to always be a stream of small bubbles in the tubing while the engine is running.

I believe all of this is pretty normal. The system has behaved this way since I took delivery of the car and it has never caused a problem. I think as long as there is not an actual fuel leak around the filter fittings or the bottom drain valve, there won't be a fuel feed problem.

Wish my old marine diesel wasn't so picky. The slightest amount of air in the fuel system and it craps out.

-Mel
 

jck66

Top Post Dawg
Joined
Jan 4, 2001
Location
Greenwich, CT, USA
TDI
12 Passat SE / 14 BMW 535d
I experienced this with my '97 shortly after I removed the mouse screen from the airbox. I goosed the pedal trying to get across an intersection and wound out first gear. It resolved itself within the (panicky) 0.5 miles it took me to get home.

Unfortunately, I don't have an explanation, just an anecdote. I thought maybe the MAF was "surprised" by some extra airflow or something, but I have no way to check and it didn't happen again.
 
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