Fuel cuts out while going up hill

jhax

Veteran Member
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Jan 24, 2012
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Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Good Morning Everyone,

I am curious to know why my 96 B4V is doing the following...

I am driving on flat ground at 65mph (cruise on or cruise off). I push the accelerator down and the car speeds up, just like any car should. I get to a long hill, there is a nice one along the I-70 corridor where the front range meets the mountains, still going 65 with cruise on.

Once the car starts climbing the hill, the RPM will hit about 2500 and then drop. The car will slow down to about 60mph (roughly 2250 RPM) and sometimes it hangs out there, sometimes it accelerates again to about 2500 RPM and cuts out again.

I can put the go pedal to the floor and the behavior remains the same. This only happens when going up hill. Other than that the car behaves fine.

Thank You,
Justin
 

Windex

Top Post Dawg
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Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
I would suspect a fuel starvation issue, if the low power goes away on its own. If it requires you to cycle the key, it may be limp mode due to a boost problem.

Have you changed the fuel filter lately? Are there bubbles in the clear line going to the injection pump? What is the fuel level when this occurs? have you tried to replicate the problem with a completely full tank?
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
I changed the fuel filter 20k miles ago. No more air bubbles than normal. Full tank, half tank. Once I get to the top of the hill and flattens out everything acts normal. I have never had to cycle the key. Just get to the top of the hill. Would limp mode caused by the turbo go away by its self?
 

Windex

Top Post Dawg
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Location
Cambridge
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05 B5V 01E FRF
No, it would require (at very least) a cycling of the key - off->on. It would also set a code which could be read with VCDS (but not a generic OBDII scanner).

How long after you're going up hill does the power drop?

Can you replicate the power drop on a long gradual acceleration?

I wonder if the pickup in the tank is plugging?

What is a "normal" amount of air bubbles for you? there shouldn't be very many at all.

Trying to understand if this is starvation, if it's an airleak into the line, or a restriction somewhere.

Do you have VCDS or access to it to scan for codes?
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
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Aug 16, 2004
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'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
20K is the fuel filter change interval. I'd replace it and see if it solves the problem. You may have gotten some bad fuel that clogged the filter partially.
 

jhax

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Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Windex,
I don't find key cycling is necessary. I have never had any codes (I do have a VCDS). I could capture a run on VCDS. Which measuring blocks should I log? As for the amount of time it takes for the RPM to drop, it's a gradual drop down to about 2350 rpm (~60MPH), maybe 3 or 4 seconds from end to end then it starts to gradually accelerate again back up to 65MPH. I have not been able to replicate it on flat ground, although I've tried. Normal being a very small amount that usually occurs. This has been going on since I bought the car. It came with the original fuel hoses and it happened then too. Once there was a split in the hose I replaced them with tygon and the same thing happened.

Peter, this happened post fuel filter change two oil changes ago which leads me to believe that the filter is/was good prior to this thing happening.
 

Windex

Top Post Dawg
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Cambridge
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05 B5V 01E FRF
Interesting - any other symptoms when it happens? Any black smoke?

If not, just a loss of power, I would log boost requested vs actual when the issue is occurring - if the boost actual hits requested, then you almost certainly have a fuel issue - either a restricted supply or a problem with the pump.
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
No other symptoms. Would you happen to know what block that is in VCDS?

Good advice! Thanks!
 

Windex

Top Post Dawg
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Location
Cambridge
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05 B5V 01E FRF
Measuring block 11 if I recall - just look for MAP absolute / requested, and MAP measured - they should follow each other pretty closely, especially if you use the graphing function
 

jhax

Veteran Member
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Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Will do. I'll post results when I obtain them.
 

KLXD

Top Post Dawg
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Lompoc, CA
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'98, '2 Jettas
If it's fuel starvation I'm thinking the IQ would increase trying to maintain power???

Log that too while you're at it.
 

jhax

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Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Okay will do. Thank you.
 

jhax

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Jan 24, 2012
Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Alright folks here is the MAP log I captured. If I am correct, I started it in a 5th gear pull to as high as the tach would register. I stopped the log and captured again starting from cruise control set at 65mph heading up a hill. I am pretty confident I captured the fuel cut out toward the end of the graph.



 
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UFO

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A mile high
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2001 Beetle
I had to recently change my fuel filter due to starvation going up hill (I'm in Denver), and it had only been about 5k miles. Bottom line, we get bad fuel, change filters just like diapers.
 

sootful

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1997 Passat TDI, 2002 Golf GLS TDI
The only time I have had this scenario happen to me was with a bad fuel filter. Once I replaced it, all was good.
 

jhax

Veteran Member
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Jan 24, 2012
Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Alright, I'll start there then.
 

jhax

Veteran Member
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Jan 24, 2012
Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Right, getting this one back up. I have since changed the fuel filter and replaced all old lines under the hood with tygon lines. I am still experiencing the same issue. Car hits about 2500rpm up hill, then backs off (no matter how far pedal is pressed) to 2000rpm. I notice when I do a hard pull on flat ground, I hit a point at about 3000rpm where the motor temporarily loses power but almost immediately pulls through past 3000. Could there be some sort of limp mode situation happening at those RPM? I don't get a check engine light or anything.
 

Abacus

That helpful B4 guy
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Location
Relocated from Maine to Dewey, AZ
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Only the B4V left
I doubt limp mode is happening since, like Windex said, you'd have to cycle the key. Incidentally, I have hit limp mode and not set a code before but it always cleared with a key cycle.

You will need to log more than just the MAP, all that does is tell us what your turbo is doing, and it look like it's following requested as it should. It looks like you logged Group 011 already.

With the VCDS, grab logs of Groups when it's not performing correctly:

003:This will tell us if it's a Mass Air Flow and EGR issue
007: this will tell us your fuel and IAT temp, which will let us know if you have a misfueling issue due to a fault fuel temp sensor and if you have a boost leak in the charge air system that only shows up under load (and volume/pressure)
008: This will tell us if it's your fuel pump not delivering enough fuel
010: This will tell us if it's a charge air system pressure issue
015: This will tell us if it's your throttle position sensor
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Man, I am so glad I have folks like yourselves for a knowledge base. Thank you! I'll see what I can grab in the weeks to come.
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
I finally got around to getting logs of this. I did two separate pulls all grouped together.


Pull 1:
003



007



008



Second Pull:
008



010



015
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
It looks like my MAF Actual is struggling to keep up with specified.
 

Abacus

That helpful B4 guy
Joined
Nov 10, 2007
Location
Relocated from Maine to Dewey, AZ
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Only the B4V left
Your MAF looks fine. At lower rpms the EGR makes up the difference for the MAF, which is why it dips lower.

You have a split hose, split intercooler hard line, hole in the intercooler (or bad seams), or a bad clamp. I’ve had every one of those on various B4’s over the years. Your 010 log clearly shows the manifold pressure can’t hold despite everything else staying the same. It should not drop off like that under constant acceleration.

I doubt it’s the turbo of the MAF would show a similar trend, so it’s in the piping after the turbo.
 
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Mongler98

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Mar 23, 2011
Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
simple test, go get some plumbing fittings and plug the side that connects to the turbo, and do the same but with a valve stem on the other side right before the intake manifold. bring it up to 20 PSI. if it cant hold 20 PSI for a few minutes. if you cant keep 20 PSI for any amount of time then well, you have a leak. next fill that system up with water with some food colouring and a few drops of soap. put it back to 20psi and find out where the leak is if you cant find it when you were pressurizing. did this on my bosses cummins, turns out a seam had a crack in it from a rock strike up front on the IC. never would have found it, we knew there was a boost leak but could not find it for anything.
this worked.
 

jhax

Veteran Member
Joined
Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
Thank you both. Ill check it out. Abacus, I no longer have an egr.
 

jhax

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Jan 24, 2012
Location
Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
I have a blockoff plate. I dont think I did anything to set the value for egr in VCDS although I would have to look.
 

jhax

Veteran Member
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Jan 24, 2012
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Golden, CO
TDI
96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
For a 1z motor? I was under the assumption that the value could be changed in VCDS and that was it.
 

jhax

Veteran Member
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Jan 24, 2012
Location
Golden, CO
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96 Passat B4V, ALH engine out of a 2002 Jetta, some IE Rods and ASV Pistons. Nothing drivable yet though
I understand, thank you again. Im lucky enough to still have a job in these times, however our schedule is now 7 12 hour days on 7 days off so next week the passat will get some much needed attention.
 
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