FiTech EFI system

ken5124 said

Soooo, It's running ,, but at idle with IAC at about 7-10, every 30 seconds or so, it drops down to about 400 rpm and the IAC opens to allow air in to recover to 12 to 1300 rpm before it settles back down, and so on and so on.

Seems like a vacuum leak to me, and probably a PCV valve that is hanging open most times, and then slowly shuts down, cutting off that extra air and driving the rpm down until the IAC allows air back in.

Am I on the right track ? I will take the PCV valve out of the equation later for the next test.

Click to expand...

Hard to say. What's your afr do when that happens? Using timing control? What's the advance do when the rpm drops? How high does the iac go?

What's your initial timing at the moment? Is it verified with a timing light?

Mayne data log the idle and post some numbers or a screen capture of the data.

It could very well be a misfire or the timing is moving to try and hold idle and its not helping. Could be too lean or rich of an afr. Could be the learn value moving too fast, or the afr jumping too much at a time.

This was exactly what I had and reducing the idle learn and loop rate helped a bunch. As did making the afr jumps smaller.