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Discussion Starter · #1 · (Edited)
I have been chasing this for almost a year now. Took my car to Volkswagen to have the fuel cap replaced per recall and ever since it’s been hell. In a nutshell my car will sporadically Go into this fuel cavitation and want to misfire, stall/hesitate. ONLY fault was a below threshold fault for cats - my VW tech checked the cats and is very confident that’s not the issue. New ECU has a tune. At first I thought it was at certain positions on the fuel gauge like 3/4 full, 1/4 full, but then I noticed it just kind of happens whenever it wants to. I have replaced the following to no avail:
Fuel pumps
FPR
Fuel filter
All 8 fuel injectors
Spark plugs
Coils
Coolant temp sensor
ECU w/tune
Fuel filler cap
CCV
Smoke tested
Manifold actuators and linkage arms still good
Purge valve
Brake booster line
Fuel pump gaskets
Throttle body
Intake manifold barrels cleaned (moves freely)
Fuel pump relay
Car holds vacuum. Fuel trims are slightly lean when running “normal” @ around 7%. They should be between 0-5%. Keep in mind ECU tune voids out any emissions bulls**t.

Is there ANYTHING else in the tank that could be causing this? What about wiring? It seems that so many touareg owners have had the same problem and they keep coming back with problem resolved, replaced fuel pumps. Well they didn’t do it for me. I can’t be the only one out there that has had this issue…

**IT ONLY SEEMS TO START FAILING WHEN HOT OR DRIVING ON HOT/WARM DAYS. As long as it’s cold out, I can trust it!
 

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Wow this is a tough one. Honestly I'd see if a forum member is local and is willing to help out. Or find a Volkswagen Guru.
 

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my Former 05 gasser has a fuel tank flange recall. Is it for sure that hey replaced the filler cap and not the flange ?
 

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2006 V8 Touareg AIR, nav, hid
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In general, when you have a fuel issue after the fuel flange recall, the fix is to replace both fuel pumps. However I have never heard of any fuel issue that presented exactly this way.

I remember at least one person who had to repair the fuel pump wiring. It was damaged near the fuel flange, outside the fuel tank.

Have you replaced the entire fuel filter assembly with a new assembly. We are trying to get to all new hoses inside the fuel tank and the fuel filter has some hoses attached to it, so you replace the entire assembly.

If no luck, then at this point, I would be replacing the CPS (crank position sensor) with a OEM CPS. Don't use any generic CPS or you will have even more issues.

 

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Discussion Starter · #5 ·
my Former 05 gasser has a fuel tank flange recall. Is it for sure that hey replaced the filler cap and not the flange ?
I’m almost definite that this is how all of this started. Right after I took it in for the recall, about two or three days later I’ve got these problems. I figured they might’ve cracked the crossover piping but if that were the case I would imagine it would be doing it more consistently. It seems to be doing this at higher temperatures, it’s been pretty warm over the last two weeks and it’s been doing it since. While it was cold I could drive it all day for hundreds of miles and nothing would happen. It’s really bizarre.
 

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I'm still not clear on exactly what they replaced. Filler cap or tank flange ?
 

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The recall was for the fuel filter flange.
i know what the recall was for but th OP said they replaced the fuel filler. If he misspoke and meant the flange that's fine but I would then suggest he actually replace the cap since the symptoms could mean a clogged vent in the cap.
 

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Discussion Starter · #9 ·
i know what the recall was for but th OP said they replaced the fuel filler. If he misspoke and meant the flange that's fine but I would then suggest he actually replace the cap since the symptoms could mean a clogged vent in the cap.
Hey. Cap and fuel pumps, filter replaced… all new parts. The only thing I haven’t replaced yet are the intake suction lines and crossover line. Obviously the new pumps came with new lines, I’m talking about the other ones that are involved. I don’t think it’s those considering this is something that happens usually when I’ve been driving in warmer temperatures. At least that’s what I’ve noticed. All through the summer it was leaving me stranded, since it’s been colder it’s been driving perfect. But as I said it’s been warm all week and been giving me issues again pretty consistently.
 

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I recently replaced pumps and flanges on my Treg and while researching the topic came across two guys where the hoses inside the tank going into the filter flange came off after some driving, after installing new pumps. They did not describe the symptoms in detail but if you run out of ideas that may be something to look into.
 

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Discussion Starter · #11 ·
I recently replaced pumps and flanges on my Treg and while researching the topic came across two guys where the hoses inside the tank going into the filter flange came off after some driving, after installing new pumps. They did not describe the symptoms in detail but if you run out of ideas that may be something to look into.
Thanks man. I appreciate that but they’re secured. I really really wish that was the issue. I’ve spent so much money trying to figure this out. It’s such a clean Treg and literally nothing else wrong with it. And it’s about to get a 2.5” lift kit with fully refreshed suspension…
 

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Discussion Starter · #12 ·
Wow this is a tough one. Honestly I'd see if a forum member is local and is willing to help out. Or find a Volkswagen Guru.
I had 2 VW Mastertechs check it out to no avail. The problem is that it does not throw a check engine light when it starts to act up. And for the most part it drives normal… So there’s no way to diagnose it unless I get it to them as soon as it starts doing it. When I turn the car off and let it sit for a couple of hours it runs normal again. I think it’s temperature related, internal and atmospheric. My current mechanic is a volts wagon in Touareg Mastertech as well. He’s been a big help but it has been expensive trying to track it down.
 

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This is such a tough one, I've been in those vortexes where you just go and circles with bullshit. Believe me I have. Sometimes they're never resolved.
 

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Camshaft sensors is my bet. When they get hot the electronics go bonkers and make car hard to crank or run poorly. Once cooled down car runs fine. If it were a faulty speed sensor the car would stop running vs run poorly. Had similar issue VW could not resolve blamed on elongated timing chain. Turned out one sensor performed poorly when it got hot sending incorrect readings to the ECU, but nit throwing a CEL.
 

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Are your carpets wet? Sometimes the sunroof drains get clogged and leak into the carpets which has alot of wires in it.
 

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Discussion Starter · #16 ·
Are your carpets wet? Sometimes the sunroof drains get clogged and leak into the carpets which has alot of wires in it.
No they aren’t wet. Car stays parked in apartment garage. Now I will say I did notice the other day that my sunroof panel had small amount of water so now I need to go snake my drains. This is the first time it’s ever done this and I’ve owned the car for a long time. I’ve actually kept up with the sunroof drains.. my tech said the wiring looked okay from what could tell.
 

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Discussion Starter · #18 ·
Camshaft sensors is my bet. When they get hot the electronics go bonkers and make car hard to crank or run poorly. Once cooled down car runs fine. If it were a faulty speed sensor the car would stop running vs run poorly. Had similar issue VW could not resolve blamed on elongated timing chain. Turned out one sensor performed poorly when it got hot sending incorrect readings to the ECU, but nit throwing a CEL.
Got one one (genuine VW) on order. I’m going to replace both cam and crank sensors. Funny thing tho… when it starts stumbling, it never throws a check engine light. Can’t diagnose it without the CEL
 

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Sometimes an intermitent code may not cause a CEL, but should show up in a scan. In any event the two cam sensors and speed sensor are critical to proper timing, and just a slight signal error to ECU may cause poor operation, missfires, injection miscues, etc. One would think electronics exposed to so much heat would be hardened in some manner. Maybe the heat impacts the halls magnet , but think its the electronics. Hope this fixes the issue. If you still have car hot, hard cranking, or no start issue one of the new sensors is bad. I bring this up because happened to me. One of the new bosch sensors was toast from the start.
 

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Discussion Starter · #20 ·
Sometimes an intermitent code may not cause a CEL, but should show up in a scan. In any event the two cam sensors and speed sensor are critical to proper timing, and just a slight signal error to ECU may cause poor operation, missfires, injection miscues, etc. One would think electronics exposed to so much heat would be hardened in some manner. Maybe the heat impacts the halls magnet , but think its the electronics. Hope this fixes the issue. If you still have car hot, hard cranking, or no start issue one of the new sensors is bad. I bring this up because happened to me. One of the new bosch sensors was toast from the start.
Same exact issues happened to you????
 
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