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Discussion Starter · #1 ·
2005/126k died after fueling a couple months back, never ran it into the red before, and it died after fueling up after being on E. Pumps done at local shop in a pinch, I supplied the VDO parts to save $400, no warranty on the labor. Ran well for 4-6 weeks, maybe 500 miles. Put in a new Interstate battery during this time as well, which corrected some weird check engine light/codes as the old batt was registering around 11 volts.

Ran it one line below "1/4" parked it for 5 days. Started it up to cool it off with AC before planning to gas up and go out of town. Died in the driveway idling after 2 or 3 minutes. Got it 3 miles up the road on way to gas station - died while driving. Filled it halfway up, turned around to drive it home and park it, no stalling on that leg. Planning to drive it locally today and see what happens.

What low-fuel situation would cause this? Or is the float screwed up and I have less gas than it is showing?
 

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You beed a scan.
Stalling can have different causes.
Without a scan we will be guessing.
If the scan is clean then we can start guessing.
Next time you fill up and it dies remove the fuel cap. Evap system issues can cause vacuum inside the tank and starve the pumps. You might have an evap valve n88 issue too. But let’s not start guessing. Get a scanner or better a vcds cable for 200$ well spent. Treat it like a human being where most of the time you need a scanner or blood test to see avoid guessing. Not saying the scan or the vcds will be your salvation here. Just something to put you on the right track or prevent from taking some wrong paths to solve the issue.


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You already spoiled some expensive parts and might have caused bigger issues with the fuel pump replacement guess.


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Discussion Starter · #4 · (Edited)
No relevant (to me) codes on scan. There is no check engine light, either. There was a code for the brake booster (the hard vacuum lines are cracked, but they've been cracked for the whole 4 years I've had it and this is a new issue). I will say I do not drive the car like a granny, but nonetheless did take it on the interstate the other day and merged, foot to the floor from 50-90. The cat stunk in the cabin something awful. Smelled like it burned something off. The smell did not come back in similar attempts. The mileage started going up visibly after that. I had run a bottle of techron in that fill-up FWIW, getting ready for an oil change in 300mi.

So, remove fuel cap? If there is an evap system leak, that should register a code, no? Wouldn't the cap create another point of leak that would muddle the diagnosis?

PS: New plugs and coils a few months ago. Has a misfire code back in Dec.

PPS: As far as replacement parts thrown at it/guessing, I opted to do the fuel pumps based on 1) 16 pages on this forum going back to 2008 of 4.2s with the same exact start-stall-restart-stall condition, and 2) watching the fuel lines pull fuel on start and then not get any fuel flow after running for 10-30 seconds, in the shop bay.
 

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Do you have a scanner or did you scan it one time only?
Four years with a cracked brake booster vac hose is looking for trouble. Depends where the crack is, before or after the check valves going to the intake. Most probably after the check valve as a leak before the check valve would cause a good amount of air fuel mixture issues.
Evap system is tricky and might register a leak or a blockage. Not sure you will have a CEL on all errors or malfunction. Your cat smell is probably a good lead as that might mean a clogged cat which would also mean car losing power and eventually dying. Your cat dying might be due to the messed up fuel mixture caused by the brake booster leak before the intake juncture or another evap leak somewhere. Cat dying is mostly caused by rich mixture. Meaning less air or more fuel.
Get another scan. Clear all codes and scan again when the issue happens. We have another forum member dealing with the same issue. We are waiting for him to come back for an update. He was waiting for his vcds cable so we can do some advanced measuring blocks logging to see how his system is behaving. If you’re interested I ‘ll post the link to his thread and when you have a vcds cable I can help you log some data and compare it to mine. I have the same engine. 2004 VR6.
The filler cap trick is release any vac created by oil vapor not managed correctly by a faulty system. It might even be caused a by faulty fuel cap as it does have a valve and should be seated correctly when put back. Go through the info in the other thread and let’s pick it up from there.




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Here is the link




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Discussion Starter · #7 ·
Thanks for all the info. You said that car was a VR6 - mine is a 4.2 V8 FWIW.

I drove the car after it didn't stall in the driveway for 10 minutes. I got a half mile up the road and thought the pedal felt a little flaccid. I said to myself, I wonder if it's in limp mode now. 1 mile later, check engine light, right on queue.

I took it by autozone to have the codes read - and it appears my OBDII port has gone dead since I read codes 3 weeks ago! YAY! Just gets better and better. Tried 2 readers, went to another Autozone to try a 3rd reader......port is dead. Fuse? What fuse is it?

It may be moot because I had been living under the impression that the brake booster wasn't a big deal - my main VW tech sort of just shrugged his shoulders and never made another mention of it in the 4 years since he first saw the code. No mention that it may cause a permanently rich issue, etc. Of note, I HAVE been chasing s light stumble after either WOT and then immediately backing off (this has gone away since last year - new plugs and coils) OR after steady-state cruising for at least an hour/etc when it is well-warmed up - which sounds similar to the other member in the other post and the issue he is chasing. Backing up now, in light of your info about the brake booster plastic lines, I think I may have 2 issues - one caused by the brake booster line holes, another caused by an evap issue. It makes sense as the reason why it is only happening under extreme low fuel (and in the case of yesterday, after the car sat for 5 days absorbing ambient heat in the fuel tank. Who knows what the code is (maybe it will be a cat code) but I suspect it will be another o2 code, either of which could be caused by vac leak due to the booster lines.

Either way, code or no code, it sounds like my next course of action is to grab these booster lines, and to figure out the evap leak. Don't they have a smoke test for this?
 

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I don’t know why I thought I saw a v6 somewhere ! I’m just seeing v6 everywhere now
Well well get yourself a vcds cable really. That’s what I told the other member and honestly you will appreciate the info and the troubleshooting easiness. I just replaced a suspension module on a friends treg with the help of vcds. Without vcds we would still be chasing suspension parts and guessing which one is making fun of us. Vcds said module defective. Got a used one and problem solved. I know it is not always that easy.
Back to your issue: the vac lines costs an arm and two legs. Your best option is to get a Gates brake booster hose and dump the vw vac hoses. hose is like 3$ per 3 or 6 feet I don’t remember. 12mm inside diameter. You can reuse the check valves. Get those hoses fixed then we move on. I’ve seen a rich mixture caused by brake booster line where the guy forgot to put it back on a W12 engine, that’s a 2 VR6 craziness. I myself am chasing a rich mixture issue where my last option is to rip the brake booster lines from the brake booster to the vac pump and re-do them with the Gates hose.
Then when you get the vcds cable we can fo some testing for the evap and the other systems. You can monitor your cat temp and your fuel mixture and maf behaviour. 200$ that will pay for itself saving you from driving to auto stores for some generic code readers.
So fix the brake booster lines
Fix any vacuum hose leaks
Check the evap purge valve or valves I don’t know how many on the v8.
And get hold of a vcds cable to try to understand what’s going on with the beast.


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Sounds like a clogged cat from running rich for 4 years.
 

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Discussion Starter · #10 · (Edited)
Gates brake hoses....is this an easy and obvious retrofit for a VW tech? Sounds like a better solution to me than buying decade old plastic from VW that's been sitting in a warehouse for $ and letting it crack again. But again, this has been broken since I bought it and discovered it - but the ONLY time it stall is under extreme low fuel situations and that really doesnt have anything to do with brake booster lines.

I see the VCDS - like 1000 results. Do you have a link to the best complete scan tool setup for this?

Clogged cat. Yeah, but unless the latest code is a cat code, there have never been any cat codes. 4 years and 16k miles. And remember, the STALLING issue is only occurring under extreme low fuel situations. That has nothing to do with the cat. Guarantee it's evap, so I need to chase. Again, is a smoke test the way to go to chase evap leaks?

Didn't stall at all yesterday in 30 miles. Has a half tank of fuel now.

EDIT for PS: The OBD port fuse seems to be blown. Can anyone share the quick and dirty location and type I need? Worth a test. If that isn't it, I'm down the rabbit hole.
 

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For vcds get the real deal. No hassle:



Direct from them or a reseller but make sure you’re getting what you’re paying for.

Evap leak can not be tested with smoke. See my links in the other thread for how it works. Might be only ab evap n88 valve issue.


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Here is the brake booster hose. Get some 3 meters ( convert to feet or arms ) and reuse the check valves. Cut to the lengths you need. 10$ instead of more than 200$ for the vw hard plastic hose if it is still available .



Hose diameter should be the same as the 3.2. The 3.2 and 4.2 use the same electric vacuum pump.


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Discussion Starter · #14 ·
Just a question as I dig into this. Which fuse would I replace for the OBD port? I don't see an OBD fuse listed. I am trying to get a basic code asap
 
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