2001 VW Eurovan - mid-grade octane fuel reaps havoc

bfregon

Member
Joined
Jan 20, 2022
Location
San Diego
TDI
2001 VW Eurovan (non-turbo)
I bought this 2001 VW Eurovan about 3 weeks ago. Road like a dream for a few days – just over the moon.

Van has 170k miles on it.

Read through huge stack of service receipts from the years. Engine was rebuilt 40k miles ago! Transmission was “re-serviced” as well. About $8k total invested at that time. What a deal I got!

Then I filled the tank with some mid-grade fuel.

[Queue suspenseful music]


1 Day after filling with mid-grade, check engine light comes on.

  • Error code: 01192 – Torque converter lock up clutch (clutch circuit open)

***? Did I get duped on the vehicle sale – maybe dude cleared fault code before I came and test drove. But the transmission felt fine! Confused.

Clear fault code and pray it’s a fluke (knowing it isn’t)

2 Days after filling with mid-grade, check engine light comes on again.
  • Error code: 16684 – Random/Multiple Cylinder Misfire Detected
  • Error code: 01192 – Torque converter lock up clutch (clutch circuit open)
  • Fan stays on after turning vehicle off for a couple minutes
Ooook. Transmission still feels fine. So confused. Did I get a real lemon?

I clear codes again. I start paying a LOT more attention.

3 Days after filling with mid-grade, check engine light comes on again.
  • Error code: 16684 – Random/Multiple Cylinder Misfire Detected
  • Error code: 01192 – Torque converter lock up clutch (clutch circuit open)
  • Error code: #### (not sure which code) – Transmission Fluid Temperature Overheat
  • Fan stays on after turning vehicle off for a couple minutes
This is bad. I had already make an appointment for mechanic – really hoping I don’t have to go in. Don’t want a mechanic mucking with such a fresh engine rebuild and tranny.

So to recap, I was getting the following errors:

  1. Random cylinder misfire error
  2. Transmission fluid overheat error
  3. Torque-converter lock open error
One of the freeze frames from my drives showed I was going 7 mph. By this time I specifically felt the tranny getting squirrelly whenever I went up low grade hills.

By this time I had also read that low octane fuel can cause misfires (or pre-ignites) in older engines that call for high octane – high compression engines, like the 2001 VW Eurovan V6.

Theory -- It’s pretty hilly where we live now, and this scenario would cause what felt like excessive tranny slippage:
  1. Going up low grade hill in 1st or 2nd gear at slow speed and nominal acceleration
  2. As speed increases, tranny upshifts
  3. Random Misfire(s) from low octane fuel (theory at this time), decreasing motor power
  4. Torque-converter senses low power, down shifts
  5. High RPMs, vehicle gains speed as I give more gas, cylinders catch back up, engine has more power so again upshift
Torque-converters cause friction normally. Too much up/down shifting than it’s made for, however – this can heat up the tranny fluid. VW ECU locks the torque-converter as a precaution to reduce friction (which was causing heat).

Testing the Theory –

I had about half a tank of mid-grade fuel left, topped it off with Mobil premium (high octane)

1 Day after topping with high octane:
  • Check engine light came on only once
  • Transmission shifted notably better
I added octane booster that day after clearing fault code.

2 Days after topping with high octane, one day after adding octane booster
  • ZERO ISSUES!
4 Days after topping with high octane:

I never got error codes again. I checked for codes even though check engine light has not come back on. Nothing.

Furthermore, the freaking transmission is shifting like butter! And going up low grade hills after an upshift with zero problems – no more sporadic downshifts.

I’ve driven a lot more over the past couple days, going up low grade hills at low acceleration trying to trigger downshifts… it’s doesn’t downshift because it doesn’t have to!

The fan does not stay on after short or long road trips now.

I think it’s safe to say the mid-grade fuel did not sit well with this particular engine.

I'm keeping my appointment with mechanic today, but the agenda is very different: check spark plugs, take a gander at tranny fluid, change oil... and don't touch anything else!
 

TurboABA

Veteran Member
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
How about you start posting the actual codes\data\errors instead of telling stories.... there's a lot of info in full scans, and a lot of clues, etc.
Then, start doing logs\output tests on suspect components, issues, etc. Try to monitor things, determine patters, isolate issues, etc.
What's compression like? How old are the plugs? Are they the correct spec? Lots of unknowns!
 

bfregon

Member
Joined
Jan 20, 2022
Location
San Diego
TDI
2001 VW Eurovan (non-turbo)
How about you start posting the actual codes\data\errors instead of telling stories.... there's a lot of info in full scans, and a lot of clues, etc.
Then, start doing logs\output tests on suspect components, issues, etc. Try to monitor things, determine patters, isolate issues, etc.
What's compression like? How old are the plugs? Are they the correct spec? Lots of unknowns!
Thanks - will post printout next time.

Don't like the story? Don't read it. Search engines will index phrases that others may search for in Google, like "slow acceleration", "uphill", etc. Others may read and connect the dots.

Plus the point is that no more error codes. This may save someone lot of time and money. I have a friend that put low octane in his 2007 Audi Q7 one time and had issues like this.

Will def post other stuff next time, though. Thanks.
 

TurboABA

Veteran Member
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
Do you want to argue or do you want to troubleshoot your heap?
You're posting about a gasser on a DIESEL board..... some of us are wasting our efforts trying to help you.... but if you want to discuss SEO instead, sure......

Bottom line is, you have missfires.... this can be compression related, injection related, fuel related, air related, carbon buildup related, plug related, etc.
Without info, we don't know if it was at high rpm, high load, etc, etc, etc.
Pull the plugs.... clean them, gap them, run injector cleaner, run Seafoam, check your wires\coils whatever it has (I'm too lazy to look it up, probably coils) etc.

Even if you optimize your post so that it directs everyone who ever has a similar problem to your informative post, it won't help them.... just sayin.
 

bfregon

Member
Joined
Jan 20, 2022
Location
San Diego
TDI
2001 VW Eurovan (non-turbo)
No, really appreciate it. Was also just saying... for me, using mid-grade fuel seems to have needed up the works for several days. Topping half tank with high octane plus octane booster really seems to have resolved all 3 error codes. No more misfires, no nothing but smooth shifting and easy riding.

I posted in wrong place. Don't want to waste anyone's time. I'll delete post.

Really appreciate your reply, will take your suggestions even though all seems clear, and next time will post only pertinent data.
 

Windex

Top Post Dawg
Joined
Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
'Sides, a misfire code, even if related to fuel quality, will do nothing to aid or cause a fault with the torque converter clutch lockup.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
So, engine specifies 91 octane fuel. Owner ran 89 and had an issue. Switched to 91 and no issue.

That sum it up? ;)

OK, in all fairness, the 01P transmission in that T4 is not the best unit out there, they are a high failure item. The octane of the fuel won't have any impact on the TC lockup. You may have several problems. Normally, the 24v VR6 will "run" OK on lower octane fuel, but the knock sensor input will cause the ECU timing map to retard some, which makes the engine more sluggish... and with only 2.8L pushing a heavy brick through a power robbing 4sp slushbox, sluggish isn't exactly what you want. That engine may have a ~20hp peak output difference from fuel quality, since it probably needs the full advanced timing map to make all its 200hp, so you'll almost certainly feel it. Some engines just don't care, because their maps are just not made to take advantage of it.
 

TurboABA

Veteran Member
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
:unsure:Engine was rebuilt..... to what spec? Different compression? Or did you do all this extensive "research" to just make sure the owner's manual was correct in saying it requires 91 octane because you didn't believe it?
 

bfregon

Member
Joined
Jan 20, 2022
Location
San Diego
TDI
2001 VW Eurovan (non-turbo)
So, engine specifies 91 octane fuel. Owner ran 89 and had an issue. Switched to 91 and no issue.

That sum it up? ;)

OK, in all fairness, the 01P transmission in that T4 is not the best unit out there, they are a high failure item. The octane of the fuel won't have any impact on the TC lockup. You may have several problems. Normally, the 24v VR6 will "run" OK on lower octane fuel, but the knock sensor input will cause the ECU timing map to retard some, which makes the engine more sluggish... and with only 2.8L pushing a heavy brick through a power robbing 4sp slushbox, sluggish isn't exactly what you want. That engine may have a ~20hp peak output difference from fuel quality, since it probably needs the full advanced timing map to make all its 200hp, so you'll almost certainly feel it. Some engines just don't care, because their maps are just not made to take advantage of it.
Thanks. Someone that can read
So, engine specifies 91 octane fuel. Owner ran 89 and had an issue. Switched to 91 and no issue.

That sum it up? ;)

OK, in all fairness, the 01P transmission in that T4 is not the best unit out there, they are a high failure item. The octane of the fuel won't have any impact on the TC lockup. You may have several problems. Normally, the 24v VR6 will "run" OK on lower octane fuel, but the knock sensor input will cause the ECU timing map to retard some, which makes the engine more sluggish... and with only 2.8L pushing a heavy brick through a power robbing 4sp slushbox, sluggish isn't exactly what you want. That engine may have a ~20hp peak output difference from fuel quality, since it probably needs the full advanced timing map to make all its 200hp, so you'll almost certainly feel it. Some engines just don't care, because their maps are just not made to take advantage of it.
This was helpful info. I admittedly know only as much as I read over past 2 weeks, thus the theory and not a claim.

I know torque converter takes engine load as one of several inputs when determining when to shift up or down.

I do not know how the 2001 VW ECU was programmed to calculate engine load. Maybe someone here knows.

So I based my theory on what seems likely in my original post. Just now I read this about engine load after seeing your reply, oilhammer - general definition of what makes up engine load:

"For vehicle running on road, various loads act on the engine such as wind resistance, gradient of the road, self-weight of the vehicle, weight of passengers and luggage etc.".

Again, no idea if these (like wind resistance) are values this 2001 VW ECU considers, but I would expect loads and gradient of road to be included. I'd also expect engine load to increase as available "power" from the engine decreases.

I've also read that yes, T4 provided weak transmission and just enough HP.

So if low octane can cause loss of HP, and engine load is a factor of torque converter decision making, and torque converter shifting causes a lot of friction by nature, I thought that maybe during these times of sporadic HP loss, vehicle shifts up and down more frequently to get up the hill. RPM no doubt plays a roll. The vehicle was definitely shifting up and down at low RPMs like it couldn't make up it's mind.

Torque converter shifting causes friction, so excessive shifting would cause too much heat. Too much heat in transmission fluid, from what I've read, can trigger torque converter to lock up to prevent more shifting. That's good because more damage would be done to transmission if trans fluid keeps rising. That would explain why fan was staying on for a few minutes after turning car off before... thing was freaking hot. Fan doesn't stay on after turning car off now, either.

So would a mechanic say "Gremlins"? Doubt it. They'd probably not know what the hell happened and tell me I need to rebuild more ****, which i really don't think I need at this point.

Premium fuel - vehicle runs beautifully. Coincidence? Could anything else cause misfire codes, torque converter locks and overheating of trans fluid for a week straight, then just disappear completely right after upping octane? Just kinda doubt it.

Thanks again, oilhammer! You prompted me to get an idea of what makes a torque converter tick.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
The converter lockup strategy on those is I believe never in first, sometimes in 2nd, usually in 3rd, always in 4th. And it has to unlock for gear changes. You can monitor this information with a suitable scan tool by watching the TCM data.

The TCM monitors the lockup by simply comparing the CKP sensor value (supplied via the Engine controller) against input shaft data (supplied by its own sensor atop the transmission case). It knows that if it supplies the command to the TC solenoid for lockup, those two values should essentially be identical. Some slippage is considered tolerable, but not a lot. If it sees enough of a difference in those two values for long enough, it flags the DTC you had, and then simply stops trying, and if it happens over a couple key cycles, it will send a MIL request to the ECU, which in turn tells the Instruments to turn on the MIL. If you continue to drive this way, the ATF temp will increase, since much of the heat generated in an automatic is from the converter during non-lockup conditions. That transmission was designed from the get-go with a lockup converter in mind, so it simply does not have the extra cooling capacity to deal with a converter that is not locking up. Then the second TCM DTC: ATF overtemp (this is also likely why the fans ran longer.... all the heat is exchanged into the coolant, which is in turn exchanged to the air via the radiator and fans).
 

DizelDvica

Active member
Joined
Jan 30, 2008
Location
MN
TDI
2006 TDI Jetta
01P - 2002 Eurovan
Oilhammer, can you give any recommendation for replacement lockup TC? Local dealer tells me they are no longer available and aftermarket offerings are numerous from rebuilt to Chinese ?? with unknown quality. Are the 01M TC units same, assuming not?



OP:
I owned Eurovans for a long time, use 91 as default. Had filled with 87 on more than few occasions with no issues, codes, misfires. All of my engines are stock, unmodified or rebuilt. That could be main reason you had issues. Eurovan manual does state that 91 is recommended and 87 is minimum.
 

bfregon

Member
Joined
Jan 20, 2022
Location
San Diego
TDI
2001 VW Eurovan (non-turbo)
01P - 2002 Eurovan
Oilhammer, can you give any recommendation for replacement lockup TC? Local dealer tells me they are no longer available and aftermarket offerings are numerous from rebuilt to Chinese ?? with unknown quality. Are the 01M TC units same, assuming not?



OP:
I owned Eurovans for a long time, use 91 as default. Had filled with 87 on more than few occasions with no issues, codes, misfires. All of my engines are stock, unmodified or rebuilt. That could be main reason you had issues. Eurovan manual does state that 91 is recommended and 87 is minimum.
Thanks for your input.

Not sure if you may be referring to valve body, but found this very informative when reading about Eurovan TCs:


Hope that's of some use if you haven't already been there.
 
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