Rough idle

KEAHUPIE

MEMBER
VOLKSWAGEN

I've got a 1998 VW Jetta GLX (VR6) with 5 speed and with 117k miles. I have two issues that may or may not be related:
-unusually high idle rpm: hovers around 1100-1200rpm where 700 was the norm in the past. Also, the idle rpms are not as steady and fluctuate a bit more than they used to.
-after driving on a highway for about an hour, found that the car would intermittently jerk (loose power?) For a second or two. This comes and goes in small batches and can happen at any gear. The jerking is a lot more severe than if I abrubtly let gas pedal off which makes me think that it's not engine related. If I abrubtly let gas pedal off in any gear, the car slows down relatively smoothly as it should. No stalling has occured yet (crossing my fingers).
-Here are my trouble codes:
P0103 Mass or Volume Air Flow Circuit High Input
P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem
P0442 Evaporative Emission Control System Leak Detected (Small Leak)
P1544 Throttle Actuation Potentiometer Signal too High
P1580 Throttle Actuator B1 Malfunction
P1582 Idle Adaptation at Limit
-I took the throttle off to check it and all mechanisms are in good shape even the gears and potentiometer.
-AMF sensor is responsive to throttle position changes
-throttle pos. Sensor is responsive to pedal pressing (as seen in my scanner)
-Fuel filter is one year old, air filter is clean
-new spark plugs

3 Replies

LILWE3ZY05

MEMBER
5 POSTS

Double check for vacuum leaks. They seem to be a big problem, and also check your idle air control valve. If it is stuck open, that can cause higher idle.

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Thursday, September 14th, 2006 AT 8:06 PM

CAPTAINMANIACDRIVER

MEMBER
15 POSTS

VW's computer can cause the idle fluctuation to tell you of a problem. Usually you need to then clean the airflow sensor, new sparkplugs and/or timing check. A vacume leak could cause it too. On non-CIS or Difigiant the idle stabilizer need be checked more often. It seems it's your rubber boot from the air filter to the manifold because the engine moves a bit while the air filter does not, thus opening the boot even more in first gear with most torque. When full thottle you can beat the stall. There may be a hose below into the boot which also may have come loose either end.