Volkswagen Passat Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
89 Posts
Discussion Starter #1
Hi all! 2003 Passat 1.8T GLS, awm engine. Revs pulse up and down under 2000rpms under normal driving conditions, typically anything under about 50 mph, like in residential areas. About 1000rpms per pulse. Very rhythmic. Fresh air filter. Cleaned mass air flow sensor. Pcv completely redone less than three years ago. O2 readouts stick around .45-.60 under normal driving. No dash lights on (besides the washer fluid sensor going to sh!t again). Nothing unusual showing on the Carista OBD2 monitor sent to my phone. Passed NY state inspection just in July, and had the pulses then, too. Any ideas what I should be looking for?
Thanks n advance.
 

·
Registered
Joined
·
26,127 Posts
Have you cleaned the throttle body? Just to clarify, you are pulsing every 30 seconds at 2K rpm or is the engine speed going up/down by 1K rpm?
 

·
Registered
Joined
·
89 Posts
Discussion Starter #3
Have you cleaned the throttle body? Just to clarify, you are pulsing every 30 seconds at 2K rpm or is the engine speed going up/down by 1K rpm?
I’ll try cleaning the throttle body. It’s rpms going up and down, so I don’t know. I don’t think engine speed it changing, since the car itself doesn’t seem to be going faster/slower with the pulsing, and my foot is steady on the accelerator. Little more frequent than 30 second pulses. I could try to get a video of the display next time I go out, hopefully with the sound of the revs, too, if that’d help.
 

·
Registered
Joined
·
26,127 Posts
If the rpms are going up and down, the engine speed is changing or your tach has a bad connection. With any luck, cleaning the throttle body will help.
 

·
Registered
Joined
·
29 Posts
Throwing out another scenario.......If you have an automatic transmission...............and also if you have harsh shifts:
There could be an issue with the automatic transmission. There is a valve in the valve body that maintains pressure but if the pressure drops then the gears shift until the pressure increases creating another shift.
I had this problem too and I saw on my VCDS that the transmission gears were changing rhythmically and the car/engine was surging at lower rpms (mine would act up while driving around 1400-1800 RPM).
There is a kit to modify that valve but in my case I pulled a JY valve body and installed it.
BTW my 1.8t throttle body is cable controlled and not DBW.
 

·
Registered
Joined
·
89 Posts
Discussion Starter #6
Cleaning the throttle body worked. After shearing three of four bolts putting it back in. rolleyes Was our if commission until the new bolts got here. But she’s smoother than she’s been in ages. Thanks!!
 

·
Administrator
Joined
·
23,318 Posts
Cleaning the throttle body worked. After shearing three of four bolts putting it back in. rolleyes Was our if commission until the new bolts got here. But she’s smoother than she’s been in ages. Thanks!!
How the F did you shear them off? It’s not supposed to be very tight.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
89 Posts
Discussion Starter #8
How the F did you shear them off? It’s not supposed to be very tight. I guess some people don’t have the “touch”.


Sent from my iPhone using Tapatalk
I used the torque wrench, set to 7 ft/lbs. The new ones I hand tightened.
 

·
Administrator
Joined
·
23,318 Posts
7 ft/lbs still seems low for them to shear. Strange.
 
1 - 9 of 9 Posts
Top