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Quiche2192 · 10-12-2022, 07:03 PM

The engine recently started surging and I am at a loss as to finding out what could be the cause. I have read around and tried diagnosing the following:

- The engine has been rebuilt and has been tuned and been running fine for months. IACV is new.

-Went to a drift event and at the end it started surging at idle. The engine starts normally then after a while it will start raising the idle to around 1700. Timing will then drop from 15 to 0, which causes the idle to drop. Then the cycle repeats.

-Checked vacuum leaks by using a propane torch and waving it around the intake. Hasn't pointed out anything.

-Replaced the O2 sensor, but hasn't made a difference

-MAF is OEM new

-Checked timing. It was at 20deg btdc. Turned the CAS almost all the way to get it to 15. Then the engine started idling normally again, but the it doesn't run right. Throttle is not very responsive. Plus if everything is good, 15 deg btdc should be when the CAS is centered. Mechanical timing is dead on.

-I'm thinking now that it might be CAS related.

So yeah I'm at a loss. I'd appreciate any input. Thanks!

10-12-2022, 07:03 PM	#1
Quiche2192 Join Date: Oct 2018 Location: FL Age: 32 Posts: 47 Trader Rating: (0)	Redtop Idle Surging The engine recently started surging and I am at a loss as to finding out what could be the cause. I have read around and tried diagnosing the following: - The engine has been rebuilt and has been tuned and been running fine for months. IACV is new. -Went to a drift event and at the end it started surging at idle. The engine starts normally then after a while it will start raising the idle to around 1700. Timing will then drop from 15 to 0, which causes the idle to drop. Then the cycle repeats. -Checked vacuum leaks by using a propane torch and waving it around the intake. Hasn't pointed out anything. -Replaced the O2 sensor, but hasn't made a difference -MAF is OEM new -Checked timing. It was at 20deg btdc. Turned the CAS almost all the way to get it to 15. Then the engine started idling normally again, but the it doesn't run right. Throttle is not very responsive. Plus if everything is good, 15 deg btdc should be when the CAS is centered. Mechanical timing is dead on. -I'm thinking now that it might be CAS related. So yeah I'm at a loss. I'd appreciate any input. Thanks!