Erratic Idle with no CEL

[yellowbird986]

Hello,

I have a 2000 Boxster with an Evolution Motorsports cold air intake, Fabspeed exhaust and headers, and Powerchip programing. The car has roughly 50,000 miles on it and has had no major engine problems thus far. A couple months ago before I installed the exhaust and intake, I replaced the engine air filter with a K&N filter. In the process, I disconnected and reconnected the battery so the onboard computer would learn the new filter and adjust accordingly. Immediately after installing that filter, my engine started idling erratically once the engine heated up- the RPMs jump back and forth between 450 and 1000, the jumps varying from 250 to 500 RPM. There is no CEL and there are no error codes after a diagnostic was done. The MFAS is clean (no oil) and disconnecting the airflow from the throttle body has no effect on the erratic idle. When the throttle controls are disconnected from the throttle body, the idle rises a bit and remains steady, possibly indicating that some component is giving the throttle a bad signal. I'm a bit skeptical that the issue is caused by carbon buildup in the throttle body or the idle stabilizer valve because of the low miles on the car but I could be wrong. Does anyone have any ideas as to what is causing this fluctuation in idle? Initially I thought it was simply a matter of the ECU needing to be reset but I have tried this numerous times to no effect.

Thank you for your time.

[vizcarra44]

Hello,

I have a 2000 Boxster with an Evolution Motorsports cold air intake, Fabspeed exhaust and headers, and Powerchip programing. The car has roughly 50,000 miles on it and has had no major engine problems thus far. A couple months ago before I installed the exhaust and intake, I replaced the engine air filter with a K&N filter. In the process, I disconnected and reconnected the battery so the onboard computer would learn the new filter and adjust accordingly. Immediately after installing that filter, my engine started idling erratically once the engine heated up- the RPMs jump back and forth between 450 and 1000, the jumps varying from 250 to 500 RPM. There is no CEL and there are no error codes after a diagnostic was done. The MFAS is clean (no oil) and disconnecting the airflow from the throttle body has no effect on the erratic idle. When the throttle controls are disconnected from the throttle body, the idle rises a bit and remains steady, possibly indicating that some component is giving the throttle a bad signal. I'm a bit skeptical that the issue is caused by carbon buildup in the throttle body or the idle stabilizer valve because of the low miles on the car but I could be wrong. Does anyone have any ideas as to what is causing this fluctuation in idle? Initially I thought it was simply a matter of the ECU needing to be reset but I have tried this numerous times to no effect.

Thank you for your time.

Well the carbon buildup can cause this issue, just clean it and then when you turn key on, dont start and dont step on throttle, let e-throttle adapt for about 1 minute then switch off ignition for 10 seconds, then just drive it, see what happens. Otherwise maybe the stuff you installed is causing the problem, such as K&N filter.

vizcarra44