Piston Slap: Getting in the Zone, Audi A4 1.8T Edition

Sajeev Mehta
by Sajeev Mehta

C.T. from AutoZone (yes, that AutoZone) writes:

Dear Piston Slap, I drive a 2002 Audi A4 1.8T with the CVT. It has 75,000 miles on it, and has been properly maintained. I am experiencing a vibration under these conditions:’

-Only after at least 10 minutes of driving…never cold

-Only between 70-80 mph

-Only when accelerating

-The same no matter how much throttle I give it

-I cannot feel it in the steering wheel

-It feels like it is coming from the axle/drive shaft area

-Sometimes it doesn’t happen at all

I recently took it to a reputable independent shop I have used several times to perform the timing belt and drive belt swap recommended before 80,000 miles. I mentioned the vibration, but they could not replicate it (although I am sure they drove it cold). The vibration was happening maybe 1-2 days a week then. Now it is happening 9 in 10 days under the conditions above. This is probably the only place I trust with my car where I live, but they are so busy right now that I’m afraid they still won’t take the proper time to do a 20-minute highway test drive to properly diagnose the problem.

I don’t have the time, the tools, or the skill to DIY this. I have searched the Audi forums for answers and most blame their mods for their vibrations. I’d like to be able to give my shop a better idea of what it might be…they are more likely to spend the time looking at the car on a lift than test driving, so if I can get them going in the right direction, maybe they will find and fix it.

Help me Piston Slap, you’re my only hope.

Sajeev answers:

And with that: help me, Best and Brightest! This week’s Piston Slap comes from India and Internet access is, uh, somewhat limited. And intimate knowledge of CVT repair/diagnosis is quite hard to find outside of a stealership service bay. But that’s not to say that CVTs aren’t worth their weight in gold to someone.

I reckon you have a mechanical problem internal to the CVT, since you mentioned that the problem happens as the car’s fluids warms up. Failing sensors or worn CV joints need not apply, but a used CVT from car-part.com runs $800-1000 and the labor is several hundred more. That’s probably your only route, as locally rebuilding a CVT is almost entirely out of the question given the complicated nature of CVTs.

If your mechanic is still clueless after the road test, I suggest a change of plan: add a bottle Lucas (purchased with your AutoZone rewards card, wink-wink) and sell it to a faceless dealership, or Carmax. Bad Karma to the next owner be damned, I suspect far, far more terrible financial pain in your future should you not heed this advice.

And if you’re a modern hot-rodder who loves getting on the boost, I’d recommend choosing a more robust platform for your future modifications. You know, if you did that in the first place.

[Send your queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • Pch101 Pch101 on Sep 01, 2009

    I don't know why tires and suspension wouldn't be the first things to check. These can be inspected for wear, imbalance, etc. without replicating the problem itself. I would suspect some combination of these as the culprit. Edit: I missed the above post about the problem being solved. Sorry about that.

  • Psarhjinian Psarhjinian on Sep 01, 2009
    I don’t know why tires and suspension wouldn’t be the first things to check. These can be inspected for wear, imbalance, etc. without replicating the problem itself. I would suspect some combination of these as the culprit. I think it was because he noted he didn't feel it through the steering wheel. Usually you'll feel (and see) the imbalance that causes as vibration in the wheel. I kick myself for not thinking about the motor mounts. My Saab busted two over a period of six months and exhibited about the same symptoms. I think the lesson here is that we all distrusted the CVT and were too willing to find it at fault, or we didn't listen to his description of the issue.
  • Ronin The very asking of the question "Are Plug-In Hybrids the Future?" is an interesting one. Because just 2 or 3 years ago we'd be asking- no, asserting- that E cars are the future. We're no longer asking that question.
  • Peter Benn There apparently were some K-code 4-dr sedan Fairlanes. Collectible Automobile Apr 2024 has found a '63 500 with HD 3/spd.
  • Mia Hey there!I recently stumbled upon the Crack Eraser DIY Windshield Repair Kit (check it out here: https://crackeraser.com/collections/diy-windshield-repair-kits) and decided to give it a shot on a small chip in my windshield. I have to say, it worked like a charm! Super easy to use, and it saved me a trip to the professionals. If you're dealing with a similar issue, this kit is definitely worth considering. 😊
  • Rust-MyEnemy Whoa, what the hell is wrong with Jalop1991 and his condescension? It's as if he's employed by Big Plug-In or something."I've seen plenty of your types on the forums....."Dunno what that means, but I'm not dead keen on being regarded as "A type" by a complete stranger"" I'm guessing you've never actually calculated by hand the miles you've driven against the quantity of gas used--which is your actual miles per gallon."Guess again. Why the hell would you even say that? Yes, I worked it out. Fill-to-fill, based on gas station receipts. And it showed me that a Vauxhall Astra PHEV, starting out with a fully charged PHEV battery, in Hybrid mode, on my long (234-mile) daily motorway daily commute, never, over several months, ever matched or beat the economy of the regular hybrid Honda Civic that I ran for a similar amount of time (circa 5000 miles)."You don't use gasoline at all for 30-40 miles as you use exclusively battery power, then your vehicle is a pure hybrid. Over 234 miles, you will have used whatever gas the engine used for 200 of those miles."At least you're right on that. In hybrid mode, though, the Astra was using battery power when it wasn't at all appropriate. The petrol engine very rarely chimed in when battery power was on tap, and as a result, the EV-mode range quickly disappeared. The regular hybrid Civic, though, deployed its very small electric reserves (which are used up quickly but restore themselves promptly), much more wisely. Such as when on a trailing throttle or on a downward grade, or when in stop-start traffic. As a result, at the end of my 234 miles, the Civic had used less gas than the Astra. Moreover, I hadn't had to pay for the electricity in its battery.I look forward to you arguing that what actually happened isn't what actually happened, but I was there and you were not."Regardless, that you don't understand it appears not to have stopped you from pontificating on it. Please, do us all a favor--don't vote."You really are quite unpleasant, aren't you. But thanks for the advice.
  • Tassos Jong-iL Electric vehicles are mandated by 2020 in One Korea. We are ahead of the time.
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