Idle Problem!!!!!!!

[DKew1.8t]

So, I just install after market exhaust on an 01 1.8t Jetta. When it idles it will idle at about 700 then it will shoot up to 900rpm then jump back down. Anybody got a clue what is causing this and how I can fix it?:mad:

[Mk4Gasm]

So, I just install after market exhaust on an 01 1.8t Jetta. When it idles it will idle at about 700 then it will shoot up to 900rpm then jump back down. Anybody got a clue what is causing this and how I can fix it?:mad:

It's not abnormal for a car to increase it's RPM at idle if something like say the radiator fan or the A/C or something kicks on that creates alternator drag. If you weren't experiencing this problem prior to the exhaust being on dustin than it may be something like they disconnected the battery terminal to weld on the exhaust and that may have reset a couple things on your ECU and now maybe your radiator fan will kick on right as you start your car. Try starting your car and then driving it until it's warm, turning it off, and starting it again and see if the second time you start it and idle it the RPM's increase. Although that doesn't seem like that big of a deal to me just 200 RPM's. You may also notice it now more because of the exhaust being louder and you can just hear it now.

[Mk4Gasm]

Yeah looked at my idle today at my car idles at 900 all the time, so I don't know what you're worried about.

[OrangeDUB]

The new ECU may be learning a new idle with less backpressure.

[Mk4Gasm]

The new ECU may be learning a new idle with less backpressure.

Yeah makes sense cause I always idle @ 900 RPM and I have the exact same exhaust

[iadubber]

vac leak? dirty maf? coolant temp sensor? O2 Sensor? dirty throttle body?

I personally would clean the MAF to start.