I have a 2003 Passat Wagon, V6, with a little over 80,000 miles that has developed a problem that I have not been able to get fixed: after the engine has warmed up, when driving at under 2000 rpm, the car jerks when light throttle is applied. I could also describe it as a thump or shudder. There is a small blip in the tachometer when it jerks. If I give it enough gas to cause the transmission to shift up, it does not jerk, nor does it do it over 2000 rpm. It recently had it’s 80,000 mile service and runs very strong and smoothly when given enough gas. My dealer couldn’t figure what was wrong, and after they consulted with VW decided that I must have put in some bad gas. The problem was to have gone away after 5 or 6 tanks of good gas. After that didn’t solve the problem, I went to an independent repair shop. They told me that it couldn’t be misfire because there were no codes registered. Their theory is that it is problem with the transmission, whereby with light throttle the transmission is told to shift but then slips right back down, thus the jerkiness. They couldn’t offer a solution, however. Can anyone help me figure out what the real problem is and what to do about it? Thanks.
First, it is quite likely that if a misfire is bad enough for you to notice that a code would be set. However, the computers aren’t as “smart” as many people give them credit for. So I wouldn’t be surprised if you had a misfire that wasn’t being reported.
However, what you describe is just as likely a transmission issue - probably with the torque converter clutch lockup. You need to take it to a good, local, independent transmission shop. Ask them to scan it and drive it.
Do you have something like an “O/D Off” button? If so, turn the overdrive off. This often disables the TCC lockup. If you can drive around normally that way then suspect the TCC lockup.
You might want to try driving around slowly in low gear if the transmission does not have an O/D off button or switch. See how it drives then.
Not to be contrary but I had a similar bump or multiple bumps like that only under load. I had no codes but it was one bad spark plug wire. So just because you don’t have a code, doesn’t mean you don’t have a spark problem. A good full computer diagnosis though with a good technician should spot if it is a spark issue. My diagnosis cost me $135 plus another $80 for new wires.
misselman-driving in low gear is mostly OK as long as I keep the RPMs up.
Bing-what can of shop did you go to for the diagnosis? I’m not getting anywhere with the dealership.
In most states the chain type auto parts stores will scan a car for free to see if there any codes or not. Their job is to provide a code (if one exists) to you; not to provide a diagnosis. You might try that as a quick freebie just to see if something surfaces.
There are a lot of things that can cause a symptom like this and there’s not enough info known to make much of a guess. Bing is correct about this possibly being a spark plug or plug boot issue and this could be especially true if the car still has the original plugs in it.
For what it’s worth, bad gas can and has happened but in most cases it’s a brush-off way of not admitting they don’t know. I also doubt very seriously they consulted with corporate VW and that the regional office agreed with the bad gas diagnosis.
I worked for several VW dealers and my experience with corporate VW is that they take care of things and do not tolerate wild guessing and hack jobs.
The independent shop is also dead wrong with what they told you about a misfire leaving a code. There are a number of things that can be iffy and yet no code will be set. Such is the curse of modern electronics… 
@FredT: Actually it was the GM dealer since I thought it might still be a warranty issue on my Pontiac. Don’t know what else to say except at one point I had another car towed from my home 50 miles to a transmission shop because I didn’t trust anyone in town. You either need a good dealer or Hans who has been working on German cars for 30 years.
Our 2004 Passat had a recall for faulty plug coils. If you haven’t had that done, that’s the cheapest solution to try. Usually, though, a faulty coil will consistently misfire. Still, it couldn’t hurt.
JDMERE STOLE THE WORDS OUT OF MY MOUTH…This is a WELL KNOWN ISSUE in the VW Audi world and one issue that I have fixed many x before…I believe one batch of Bosch Coils were known suspect and they sent out a VAST recall on them…does your vehicle fall under this recall? Look it up… “Bosch Coil problems VW/Audi” on the net…
Blackbird