Idle surging and rough idle

Hi and thanks for using 2CarPros.

With a properly operating PCV, you shouldn't be getting that much pressure in the crank case. As far as the leak you described, that wouldn't be a vacuum leak but rather the pressure is blowing outward. Also, there shouldn't be vacuum in the crankcase.

If the PCV is good and working (check it for vacuum) then I question if there is excessive blow by being caused in the engine due to a compression loss via rings.

An erratic idle can be caused by a vacuum leak, or an idle air control valve. But again, vacuum would be drawing in and not blowing out. You may want to perform a compression test to confirm the pressure is within the manufacturer's specs. If one or more cylinders are low, that too will cause idle issues.

Here is a link that shows in general how to check compression:

https://www.2carpros.com/articles/how-to-test-engine-compression

Here are the directions specific to your vehicle for checking compression:

Engine Compression Test

Special Tools

EN-48248 - Cylinder Compression Pressure Gauge

For equivalent regional tools, refer to Special Tools See: Engine > Electrical / Mechanical Repair > Special Tools.

Removal Procedure

1. Remove the throttle body assembly. Refer to Throttle Body Assembly Replacement (1.4L LUH and LUJ) See: Throttle Body > Removal and Replacement > Throttle Body Assembly Replacement.
2. Remove the spark plugs. Refer to Spark Plug Replacement See: Spark Plug > Removal and Replacement > Spark Plug Replacement.
3. Remove the relay holder cover.
4. Remove the fuel pump relay.

Note: The engine cranking time for the compression test should be less then 10 seconds and at 30 second intervals.

5. Crank the engine with the starter motor for 5 seconds to remove any foreign substances from the cylinders.
6. Prior to taking a compression reading, verify the cranking speed is greater than 300 RPM. If the cranking speed is below 300 RPM, repair the slow cranking speed condition before continuing with the compression test.
7. Install EN-48248 - gauge in the spark plug bore for the cylinder that is being checked.
8. Using the vehicle's starter motor, rotate or crank the engine for 4 compression strokes, puffs, for the cylinder being tested.
9. Observe the compression gauge and note the reading as the compression test is being performed. A normal cylinder reading will be indicated if compression builds up quickly and evenly to the specified level. An abnormal reading will be indicated if compression is low on the first compression stroke, starts increasing on the following compression strokes but does not reach the specified level.
10. Record the compression reading for the cylinder just tested.
11. Repeat steps for all remaining cylinders. All 4 cylinders must be tested to obtain valid test results. Record the readings.
12. Maximum pressure differential 100 kPa (14.5 psi).

Installation Procedure

1. Install the fuel pump relay.
2. Install the relay holder cover.
3. Install the spark plugs. Refer to Spark Plug Replacement See: Spark Plug > Removal and Replacement > Spark Plug Replacement.
4. Install the throttle body assembly. Refer to Throttle Body Assembly Replacement (1.4L LUH and LUJ) See: Throttle Body > Removal and Replacement > Throttle Body Assembly Replacement.

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Let me know if this helps, if you have other questions, or need help with anything.

Take care,
Joe

Welcome back:

I'm glad to help. Honestly, vacuum leaks cause all kinds of trouble. You did a good job finding it.

Let us know if you need anything in the future.

Take care,
Joe