VW lost its oomph

passat
volkswagen

#1

2000 VW Passat 4 Motion wagon, V6
129K miles

Car lags for one to two seconds when accelerating from 0. Does not stall. No warning lights. Idles smoothly. Acceleration on highway is okay, but not what it used to be. Acceleration declined gradually.

Recent services:
· Replaced air filter
· Replaced spark plugs
· Replaced fuel filter
· Replaced MAF

After the last oil change and inspection at the VW dealer a few months ago, no flags were raised by the service advisor.


Update 1

  • Tried manually shifting via the Manumatic, starting in 1st. Not a significant improvement.
  • Tried Techron Complete Fuel System Cleaner. Perhaps a small improvement.
  • Tried Poor Man’s Throttle Body Alignment. No difference.

#2

When you press the accelerator, does the engine rev high (higher than it used to) without the car accelerating at first?


#3

Engine stays quiet when pressing accelerator from stand still. The transmission behaved strangely (downshifting) a few months ago, so the local mechanic replaced the MAF. The shifting isn’t perfect, but it doesn’t seem to slip.


#4

Hello there… Your Passatt is a “Fly by wire” throttle body… Meaning there is no traditional throttle cable between the accel pedal and the engines throttle body. SO… A motor and controller actually open the throttle for you. This system can get out of adjustment. When this occurs there can be a sluggishness to the response of the throttle open/close.

Now… there are a few ways to go about this TBA “Throttle Body Alignment” which involves:

(1) the VW Dealership

(2) The use of “VAG-COM” “Volkswagen Audi Group-Communication” This consists of the correct VAG-COM cable and relevant software. Basically this is the same software used by the Dealership to perform a dizzying array of VW functions, Troubleshooting, Code Reading…etc basically everything you could want to do or see regarding the Audi/VW Engine ECU functionality. It is akin to having the capabilities of the Dealership when it comes to communication to the ECU in your vehicle. ONE of those functions is to Re-calibrate your Fly by Wire Throttle body.

(**) Then there is also the PMTBA… “Poor Mans Throttle Body Allignment” Basically this is a procedure where you get in the vehicle and turn on the ignition for between 2-4 minutes without starting the vehicle. This, according to SOME Folk forces a re-cal on your Throttle Body. OTHER Folk disagree and say that the only real way to do this is via VAG-COM… Or the Dealer (Who is using VAG-COM also).

While I cannot argue that the VAG-COM is able to perform this function…because it can, and rather easily. I have my own VAG software for my 03’ VW GTi, so I know for certain it works.

Go online and research “00’ VW Passatt Throttle Body Alignment” and you will see the PMTBA…Poor mans version… Honestly if memory serves me correctly, I think its simply turning the ignition on for 2-4 minutes without starting the vehicle…if you listen carefully you will hear the Throttle Body working itself back n forth or making noises at least. Some swear by it and say that it indeed works, I have no reason to doubt this as I’ve heard it works.

Im sorry I cannot say for certain that it works… I have the correct software and VAG cable to do this procedure in a formal manner via the software…so I’ve never tried it without… It SHOULD Work however.

See whatcha get… Look up the search parameter I gave you…and that should guide you thru the procedure without using the software… I know the procedure is all over the net…so you will find it. Good Luck and let us know how you make out.


#5

@Honda_Blackbird:

Thanks for the info on Throttle Body Alignment (TBA) techniques.

I went through the VW forums and found the information to which you referred. I tried one of the free “recipes”, or chicken dances, as they are called. Half of the folks swear it works, half swear it doesn’t work, and the third half don’t swear.

For me, the free recipe didn’t solve the problem (perhaps the TBA worked but was not required), but it was a harmless exercise worth a try. Many of the issues these folks were trying to solve involved poor idling. The idle on my VW is very steady (by ear and by tach).

Before trying the paid options (1) or (2), I will search some more to see if the TBA solved a case similar to mine.


#6

@tiffany000007, are you related to Yogi Berra?


#7

@jtsanders,

My math, I learned from Click and Clack; so they are more closely related.


#8

@Honda_Blackbird Hey blackbird long time no see glad you are O K and back


#9

It sounds like you’ve done all the obvious things for reduced power problems … hmmm … other possibilities beyond what’s mentioned above, for reduced engine power and no diagnostic codes, fuel pressure problem or exhaust system is partially clogged.


#10

@GeorgeSanJose
Re: fuel pressure or exhaust clogged

Any DIY testing options, using MacGyver-style tools, without doing major surgery?


#11

No, testing fuel pressure and for exhaust system clogs requires more sophisticated measurement tools than that. Note that just b/c there are no dash warning lights doesn’t imply there are no diagnostic codes stored in the computer’s memory. If you haven’t actually checked for diagnostic codes, including pending codes. that’s the first place to start. Poor acceleration can be caused by low compression too. Usually that would show up as hard to start, but not always. Again you’d need a specialty tool to measure compression. I’ll add that anytime hesitation on rapid acceleration is the symptom, a thorough check for vacuum leaks is warranted. A vacuum leak will make the mixture go lean right after you step on the gas. But it might not show up at idle, as the O2 sensor feedback loop is able to compensate at idle. A vacuum leak might well set a lean code in computer memory, but not trigger a dash warning light. Fuel trim would be something a pro mechanic would probably check for this symptom too.


#12

Re: “A vacuum leak will make the mixture go lean right after you step on the gas.”

When I had the car scanned at Pepp Boys, they found no fault codes. Trust, but verify. So, I got a VAG-COM KKL cable and installed the VCDS Lite software. The engine scan found one fault:
17539 Oxygen Sensor, B2 S1 Internal Resistance too High
P1131 - 31-10 – Intermittent
Translation: [Driver side pre-cat sensor]

I’m not clear on whether this is realted to my initial problem, but since I have an emissions test coming up, I guess I can’t ignore it. The firmware was updated by the dealer 4 years ago (to version 0050) - I believe that was also related to an issue with O2 sensor.

Some opinions suggest first testing for vacuum leaks before tackling the O2 wiring and sensor, as they can cause the same fault code.

If I register ($99) the VCDS Lite software, will the other tests (block 032) reliably determine if there is a vacuum leak?

I cleared the fault code and will check again for faults in a few days.


#13

Vacuum leaks or any other route that unmetered air enters the engine can cause O2 sensor codes. Since vacuum leaks are such a common problem, mechanics usually can find them without much difficulty. They have special tools and procedures on hand for that. I’m not familiar with the details your software package, but diagnostic software – while it can flag the3 effects of a vacuum leak – isn’t a good way to determine where the vacuum leak is located.

Internal resistance too high for an O2 sensor, that’s a new one for me. There’s more than one type of O2 sensor and maybe you got one of theother kinds, but the versions I have experience with, they output a voltage, and their internal resistance isn’t monitored. You may have another type, or you may have a heated O2 sensor, in which case that might mean the heating element is intermittent. It could also mean the connector isn’t making a solid connection from the harness to the sensor.