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flightlead404 flightlead404 is online now
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Join Date: May 2015
Posts: 801
OK Steve, looks like we're back in your court with this low RPM stumble on start up. I can pretty much reproduce this at will.

I just did 5 start tests.

For tests one and two, a cold start, and a slightly warmer start. The only change from my prior data was to swap the connector for the lambda valve from the Microsquirt to the original CIS connector for these 1st two tests. Lambda duty cycle controlled by CIS, I assume at 50% give or take. There was no initial low RPM stumble on either start.

3rd test I simply reconnected the FCIS to the lambda valve and confirmed that the low RPM stumble came back as before.

For the 4th test, with the FCIS still connected to the lambda valve, but disconnected power to the AFR. This test did cause the initial low RPM stumble for 15 seconds as before. This eliminates any possibility of the AFR calibration sequence screwing things up.

5th test was the same as the third, back to all FCIS connected and confirmed the stumble remains.

The low rpm stumble period seems to last anywhere from 13 to 24 seconds in my observations. It may be shorter the hotter the engine. The low rpm stumble ends exactly where the lambda frequency duty cycle makes a sudden drop of about 2%.

Can you think of any reason why the lambda valve duty cycle is changing? EGO control is off, and indeed it happens with the AFR even connected.
Old 04-30-2017, 04:50 PM
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