FIDLE PWM signal noise
Posted: Fri Aug 23, 2013 11:26 pm
Hi,
I am running MS-2 on a V3.0 board with 2.892 FW. I am using a bosch 3-wire fast idle valve. I've got a Glen's garage-type circuit driving the valve. The warm- up curve does modulate the valve, but at every duty cycle one side of the valve has way more voltage. The closed side gets 0-2 volts rms, while the open side gets 9-11 volts rms. So, I can modulate the valve from about 85% to 100% open. I think I have traced this to the IDL-1 signal coming out of the MS-II daughter board. The attached image shows the PWM signal on the scope. The zero part of the duty cycle looks okay, but the positive part seems to have a lot of high frequency noise on it that prevents it from pulling all the way up. The inverse of this signal has a good positve part, but a noisy "zero" that never pulls all the way down. Hence the valve bias towards open. Has anyone seen this before? shouldn't the IDL-1 signal be a nice square wave, without the noise? BTW the signal was captured with the engine off. Any help would be greatly appreciated.
I am running MS-2 on a V3.0 board with 2.892 FW. I am using a bosch 3-wire fast idle valve. I've got a Glen's garage-type circuit driving the valve. The warm- up curve does modulate the valve, but at every duty cycle one side of the valve has way more voltage. The closed side gets 0-2 volts rms, while the open side gets 9-11 volts rms. So, I can modulate the valve from about 85% to 100% open. I think I have traced this to the IDL-1 signal coming out of the MS-II daughter board. The attached image shows the PWM signal on the scope. The zero part of the duty cycle looks okay, but the positive part seems to have a lot of high frequency noise on it that prevents it from pulling all the way up. The inverse of this signal has a good positve part, but a noisy "zero" that never pulls all the way down. Hence the valve bias towards open. Has anyone seen this before? shouldn't the IDL-1 signal be a nice square wave, without the noise? BTW the signal was captured with the engine off. Any help would be greatly appreciated.