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Discussion Starter #1
Well, I figure it's about time to get around to creating this thread now that I have access to a scanner that can pull codes and communicate with the car.

As a background, I started driving this car heavily right around wintertime in Ohio, so it lived in below freezing weather up until late February. Around mid April / May (50 deg F or above at the time), I started to notice lacking power, as did my passengers. The car really doesn't like low RPM. If the car is traveling up a slight incline in 5th (maybe going around 40-45mph), it'll unlock the torque converter to compensate. The car will rev up to 3000 RPM and barely accelerate.


The dirty old stock MAF crapped out on me on my way to work around two months back, so there's a new Bosch one in it's place.
Old Bosch +4 spark plugs have been replaced with a set of Bosch plugs with two ground electrodes from ECS.

Now here's the weird part. When the temperature drops to below 65 F, the car might as well be brand new. Throttle response, torque, low end power, and acceleration are all back and my cruise (which doesn't work most of the time) is fully functional.

CODES:
18057: Databus drivetrain,missing message from ABS control module - Active/Static
17530: 02 Sensor Heater Circ., Bank2-Sensor2,Open circuit - Active/Static
17548: Bank 2, Sensor 2,internal resistance too high - Active/Static
17887: Brake vacuum system,mechanical malfunction - Active/Static
16995: Cruise Brake Switch (A) circ.,Malfunction -Passive/Sporadic
16805 Warm Up Catalyst, Bank1,Efficiency Below Threshold - Active/Static
17831: Bank1, secondary air system, Flow too Low - Active/Static
17819: Bank2, secondary air system Flow too Low - Active/Static

TCM
17087: Torque Converter/Brake Switch B Circ.,Malfunction - Active/Static

Almost all of the ECU codes will come back within a day or two of clearing them, so my futile attempts to get rid of my MIL was thwarted pretty fast. The car is perfectly operable and it still gets me from point A to point B without falling apart, but things not working right tends to literally keep me up at night. I haven't seen the TCM torque converter code any time recently. From what I can see from scanner live data, Fuel trims are okay, but tend to hover a little negative (2-4 percent) when it's warm. IAT sensor reads about 37 C (98.6 F) when its around 75 F out, which doesn't seem too off, given that it runs through the piping in the engine bay.

The car likes to misfire randomly when ambient temp is higher as well. It isn't enough to throw a code, but sitting at idle, you can feel and hear it.

Any info is helpful.
 

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It looks to me like a transmission problem and you are investigating it as an engine problem. The loss of power on a slight incline in 5th, you determined it was 5th using tip mode? That’s all I got. If you’re using tip mode already to diagnose.
 

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Discussion Starter #3
It looks to me like a transmission problem and you are investigating it as an engine problem. The loss of power on a slight incline in 5th, you determined it was 5th using tip mode? That’s all I got. If you’re using tip mode already to diagnose.
I was moving around 50mph and yes, I slid the shifter into Tip mode to see if it had downshifted. Putting the car in tip mode forces the torque converter to lock up (which I assume is to give it a more "manual" feel).
 

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“Slid back into 5th on a slight incline at 50”. I use tip mode more and more now and I might do that myself in a normal course of driving. “ Feeling misfires at idle”, maybe it’s the transmission, and not misfires? How are the spark plugs? Clean or oily ?
 

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Discussion Starter #5 (Edited)
I'm fairly confident that it's a misfire. Engine RPM drops for a sec and I can hear it from my little exhaust leak in the flex pipe. Off-idle / under load, there is no misfire that I can feel and there's no codes. Could the ABS module being out cause any of the driveability issues?
 

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Don’t think so about the ABS. I’m at a loss as I’m not an expert mechanic. Interesting though about the temperature factor. Something has to give. Meanwhile, the summer is nearly over and the car will be good as new again.
 

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Is it possible you have an air leak that is so slight it only manifests in warm weather? Also I once discovered a collapsed hose no holes and no codes. It ran under the coolant reservoir and was braided in fabric and unmistakably completely collapsed like it was trying to black hole itself. I replaced it with a thick walled silicone. Another interesting one I had was a pinhole leak in a check valve coming from a hose that comes out of the top of the engine, but misfire codes came along with that.
 

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Discussion Starter #8
I had a bunch of the vacuum hoses replaced last year when I had the TB done. The brake vacuum pump doesn't seem to be working, which would cause the 17887 code. I might have to comb through my vacuum lines and try to find any sign of leaks.

And as rayj said, winter rolling around means the car will run well for the time being. The temperature part is what confuses me the most. I am at a loss as well.

Side note: are the screws on the vacuum pump torx or triple square? I know they're not allen.
 

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Side note: are the screws on the vacuum pump torx or triple square? I know they're not allen.
ETKA doesn't have an exploded view of the pump so I don't think it's meant to be serviceable. The top looks like torx but there are some other screws that go from the bottom up I think and the heads might be different. I've only had to deal with triple square bits in one area so far, somewhere in the trunk lid of my Passat wagon. I've read in some cases it's possible to substitute a torx bit for a triple square bit but you risk stripping the screw. If you're in a bind maybe you could try that.

97334


You could try researching its part number 8E0927317A for more info. Here's a guy who saved his by cleaning the gunk and then greasing it but he doesn't show how:
 

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Discussion Starter #10
I ordered a fuel filter from ECS. I'm gonna try to check / fill the transmission fluid (my thoughts being that it's low but low temps making the fluid more viscous, offsetting the TC slip) before I start diving into parts or just getting rid of the car all together. I love her, but man she's fussy.

I've been thinking about a full fluid and filter change, but given the lack of service history and 191k miles, I don't want to have the tranny start slipping on me. In reality, I would like to do a manual swap but budget issues, part sourcing, and the fact that the car has so many other issues would make that kind dumb from a logistical and financial point of view. Why dump thousands into an okay condition, high mileage car when I can go buy an A4 or a more suitable car?

Love for cars is something strong, I tell ya.
 

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I had my trusted transmission service guy do a fluid change and I’m sorry I did. He’d been in business at the same location for probably 35 years , more or less apprenticed himself to the owner out of high school and eventually bought him out. Also he was a part of a friendly group I palled around with sometimes. I say this to show I fully trust him. I took it to his shop, ( he had 3 or 4 employees ) because sometimes my trans remained in first far too long to upshift when cold. His mechanic employee did the work. Within a week or so, I got a loud bang out of the underside of my car, and a noticeable bump now when it downshifts from 3rd to second. In hindsight now, it becomes clear to me that my friend did thw service because I asked him to, not because he was convinced it was necessary. Point 2 in hindsight, his mechanic might be a bit of a yahoo. So I caution to let your mechanic guide the job. Let it be his decision according to his expertise. The old “don’t fix it if it ain’t broke” really bit me. It will be a $300 + job and fluid level must be checked at a certain temperature. Well maybe you or someone else out there know more about the job and I’d love to hear about it.
 

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Discussion Starter #12
There's a ton of threads out there about doing fluid changes and basically anything to do with transmissions. My little scan tool can check transmission fluid temps and I have a buddy with a big garage and a two post lift. I'm hesitant to do a full change do the mileage and lack of service history.
 

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The flaw in the logic is that there’s usually an existing problem that causes someone to do the fluid change at high mileage. About the only realistic problem caused by new fluid alone would be clutch slippage on worn plates assuming the new fluid had lower friction than the old fluid. The “freed crud in tiny passages” is unlikely since not much gets past a filter, esp if it’s old and mostly clogged.
 

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Discussion Starter #14
The flaw in the logic is that there’s usually an existing problem that causes someone to do the fluid change at high mileage. About the only realistic problem caused by new fluid alone would be clutch slippage on worn plates assuming the new fluid had lower friction than the old fluid. The “freed crud in tiny passages” is unlikely since not much gets past a filter, esp if it’s old and mostly clogged.
That's my issue. If I'm being honest, I can't really afford to have a transmission start slipping. I don't have the time to try to rebuild it myself, let alone even getting it back together.
 

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Discussion Starter #15
Reviving my own dead thread a little bit here, but I thought I would share an update with you guys.

I just decided to deal with the issue until the cold rolled around (which this winter, seems to be never). A while back, I found this thread about somebody with an 05 A4 with a very similar issue. They're solution was a brake light switch, which makes a little bit of sense if you squint your eyes and turn your head.

But anyways, the traction control in my Passat decided it wanted to permanently disable itself the other night, which solved my issue. 60 degrees F and the engine feels like new again.

I believe I've made the decision to make this my dedicated winter ride despite the lack of rust. It eats through snow like no other car I've ever driven, and the heat is torching hot.
 

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Bit of my 2 cents:
In my 2.8 v6, I had misfire issues after it rained. I replaced my coil pack and that fixed that.
also wondering if your ECTS is shot or having issues, so your car gets the wrong A/F ratios, which is why it is fine in certain temps but not in others.

all the misfires and horrible A/F ratios would lead to all the crap with your o2 sensors.
 
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