05 Passat TDI having weird problems (hard to tell if fuel-related)

ybiofuels

Veteran Member
Joined
Jun 17, 2003
Location
Ukiah, CA
TDI
2003 silver Jetta wagon
Hello everyone,

As some of you may know, when all else fails, and I have a genuine TDI mystery to solve, I tend to post here and see what the collective thought process can yield. I've always appreciated your input in the past. Here's the latest:

Hi Kumar,

Here is a summary of what has been going on with my Passat 2005 TDI wagon:

On Sept. 9, I got in my car to go to a friend’s. It started fine but could barely make it up my driveway (8-9% grade). I continued at half power 1 mile up my dirt road (also a grade) to the main road. I knew I could make it to town (downhill) but didn’t think I could make it home again, so I turned around there and went home. There were no warning lights on the dash to give me a clue what was going on. At that time I had about 90% biodiesel in the tank, 10% diesel #2.

The next day I had to unload something at the cottage and drove up my driveway with no trouble at all, perfectly normal.

The next day was a Monday and I called my mechanic. He was booked but squeezed me in on Tues. for a new fuel filter. We both hoped that would fix the problem.

I picked it up and drove it all around for 10 days, including to Potter Valley and back (4 1/2 hours round trip). On Friday Sept. 22, I started off to my physical therapy appointment in Ukiah, 2 hours away. I realized right away that I had only half power, like before. I decided to drive about 15 miles, to see if it would correct itself. It didn’t. At Point Arena I stopped and went into the clinic to call and cancel my PT appointment. When I came out, the car started and drove perfectly. (But I was now too late for my appointment.)

The next Monday, Sept 25, the car had its 40,000 mile service. Everything checked out fine.

On Friday, Sept 29, I was going to a friend’s, and it happened again. I turned on the car, and while backing up could tell I had only half power. So I turned the car off right in the driveway, waited 2 minutes, and turned it on again. This time it was working fine and I drove to my friend’s house.

I live on the coast and the temperature has not been below 50. The temp does not seem to be a factor. I have put more diesel in the tank, so the percentage is about 50-50. This is not something I intend to do for the future, however.

It has been driving fine since the third incident, and I hope this mystery gets cleared up!
Although the customer has brought the car to a mechanic, I do not believe that a VAG-COM has been run on it. I've been trying to reach Steve Ahl, and coordinate that.

The customer has used a mix of fuels, including from my company.

With the older TDIs, when all else failed, we could open the top of the fuel pump and see what there is to see. I don't know if that's possible with these newer ones. I will be very grateful for any guidance.

-Kumar
 

nh mike

Top Post Dawg
Joined
Apr 28, 2002
Location
NH
TDI
2003 Jetta GLS wagon, 2004 Passat GLS wagon
My first thought was to check the MAF, but if it started working fine again after the initial "half power" incident....
 

mudshark

Veteran Member
Joined
May 25, 2005
Location
Los Angeles CA USA
TDI
Passat Wagon 2005 Northern Green
I don't have time to find the threads right now, but this is something that myself and others have experienced. Last year, it happened to me three times, within a few weeks of each other. Hadn't happened again until last week...

I'd turn the car off then right back on again and the problem went away...

I don't think anyone ever figured it out...when I get some time I'll see if I can find the threads.
 

ybiofuels

Veteran Member
Joined
Jun 17, 2003
Location
Ukiah, CA
TDI
2003 silver Jetta wagon
nh mike said:
My first thought was to check the MAF, but if it started working fine again after the initial "half power" incident....
I rode that same thought train. Other thought was potential emulsion from small amount of soap and water, sitting in top of fuel pump funking things up (seen this in another car), but that had different symptoms too. This really sounds like a sensor thing, but I'm not the remotest of experts on these newer TDIs (not that I don't have a major vested interest- beyond the customers, my wife and I currently drive an '06 Golf TDI with lovely lovely tiptronic)

Oh, and mudshark, thanks, and good luck finding that stuff.
 

ybiofuels

Veteran Member
Joined
Jun 17, 2003
Location
Ukiah, CA
TDI
2003 silver Jetta wagon
Thanks again mudshark. That first linked thread is a real trip to hell. Man! VW sure sucks in a lot of ways.

Turbo vanes? MAF? N75 valve? Fuel temp sensor? Argh, so many possibilities. I don't *think* there were any problems with the fuel in this case, although with the mix the customer was running, it might be hard to find out. We test all of our fuel, but that doesn't mean it can't create mysteries that we must solve.

Well, 2 developments: got an e-mail from Steve, so maybe we can VAG-COM this car soon, but the second development is that the customer will be gone for a few weeks, so things are effectively delayed until then. Will report back.
 

CaJones

BANNED
Joined
Jun 8, 2006
Ironic, I just had the same problem this morning, engine just had no get up and go. I stopped to get some coffee, started it up, and the Passat ran fine the rest of the way in.

I'm currious, why is it that after looking at the previous thread from last year, this seems to be a late September /early October type of pattern that it occurs. Anyone else notice this? Is it fuel related or temp related? Or Both? I'm running B99 right now, but I think it's time to start splash blending.


It seems to happen to me only first thing in the morning when its cold. Maybe I'm pushing the car too hard when it's cold, I was running late this AM?
 

mudshark

Veteran Member
Joined
May 25, 2005
Location
Los Angeles CA USA
TDI
Passat Wagon 2005 Northern Green
Kumar, add to your list of possibilities, "a vacuum line to the wastegate was cracked? Maybe a line to the N75 valve?"

Please keep us posted. Since I've had the same problem, I'd sure like to know what the cause is, should you find it...
 

mudshark

Veteran Member
Joined
May 25, 2005
Location
Los Angeles CA USA
TDI
Passat Wagon 2005 Northern Green
CaJones said:
I'm currious, why is it that after looking at the previous thread from last year, this seems to be a late September /early October type of pattern that it occurs.
Passats hate Autumn?

CaJones said:
Is it fuel related or temp related?
Since the guy who made the post in the Passat forum wasn't running bio, I don't think it's bio related...

CaJones said:
It seems to happen to me only first thing in the morning when its cold. Maybe I'm pushing the car too hard when it's cold, I was running late this AM?
My instances of this have always been when I first start up the car for the day, regardless of whether that was a.m. or p.m. I don't think it has anything to do with "pushing the car too hard."
 

MojoDiesel

Well-known member
Joined
Jul 2, 2006
Location
Valdez, Alaska
TDI
2005 Golf TDI
2006 Jetta - intermittent lack of power, engine light on

I have 4700 miles on my 2006 Jetta and have run B100 from tank 2 onward. Never any problems until today. Started noticing a slight delay from stepping on the pedal and getting acceleration. Then it dogged for about 15 seconds. I was coming to my destination so I shut it off. The rest of my day has been mostly normal - maybe some slight hesitation. The engine light is now on all the time.

This seems similiar to some others in this thread - but I haven't seen anyone writing that their engine light is on.

Any ideas?

Thanks!
 

MojoDiesel

Well-known member
Joined
Jul 2, 2006
Location
Valdez, Alaska
TDI
2005 Golf TDI
A bit more info

Someone was asking if maybe the colder weather has something to do with this hesitaton - limp mode problem.

I just noticed that my fuel is clouding a bit - and experiments show that this starts at 47 degrees. (Close to todays temperature). Might be coincidence. I am going to start blending 20 % dino which drops the cloud temp 16 degrees lower and see if the problem goes away. I doubt that it will have any effect.

My CEL is stuck on still. (Anyone know how to clear the CEL?)
 

mparker326

Veteran Member
Joined
Feb 28, 2005
Location
Knoxville, TN
TDI
Golf 2002 Gray
MojoDiesel said:
Someone was asking if maybe the colder weather has something to do with this hesitaton - limp mode problem.

I just noticed that my fuel is clouding a bit - and experiments show that this starts at 47 degrees. (Close to todays temperature). Might be coincidence. I am going to start blending 20 % dino which drops the cloud temp 16 degrees lower and see if the problem goes away. I doubt that it will have any effect.

My CEL is stuck on still. (Anyone know how to clear the CEL?)
Why not find out what the code is? Autozone reads for free.
 

MojoDiesel

Well-known member
Joined
Jul 2, 2006
Location
Valdez, Alaska
TDI
2005 Golf TDI
CEL cleared and no problems now

Before I could read the CEL code the light went off and I have never had another problem. It's been a few weeks now. I'm still running 20% dino now and plan to continue through the cold season.

Thanks for the replies.
 

Dimitri16V

Top Post Dawg
Joined
Jan 30, 2005
Location
DE
TDI
01 Golf, 04 Golf
This sounds like the problem I have been having with my 04 PD all last summer. Car would loose power randomly, turn it off and sometimes power would be back. CEL would come on and turn itself off after power was back . No turbo wistle , AC would not work. I scanned the ECU , the code was P0652 ( ???) , it was the reference voltage to MAF. I measured it and it was 2.5V instead of 5V. changing the MAF did nothing. Pulled the ECU made sure the connections were dry and tight. I had my mechanic do the TB and change the water temp sensor and have not had the problem resurface but I will wait till next summer to verify it. I noticed this only came up as the weather warmed up.
I suspect this is a grounding problem with the ECU. Last time the ECU/harness was touched was by the dealer when they performed the recall for bad grounds. I will install a ground wire from the grounding screw to the (-) pole of the battery and see what happens. But this a scary situtation, to loose power when merging on a highway.
 
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leicaman

Top Post Dawg
Joined
Dec 24, 2004
Location
Sheboygan, Wisconsin
TDI
2015 Golf TDI SE, 2005 TDI GLS, RIP
Actually if the CEL went off, the car will still store the code that was spiked, unless the code was cleared of course.
 

MojoDiesel

Well-known member
Joined
Jul 2, 2006
Location
Valdez, Alaska
TDI
2005 Golf TDI
Still not a repeat of the problem

Thanks - seems like this problem could be due to a lot of interelated causes - MAF, stuck turbo vanes, bad wiring... the problem with fancy control systems is that they can be almost impossible to troubleshoot. The day I had the problem was about 70 degrees. The CEL stayed on for a couple days but the limp mode and hesitation only happened over the course of a single 20 minutes period a month ago.
 
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