restricted intercooler observations

2014 Chevrolet Cruze Eco 1.4 Turbo

After having a PCV mishap, replaced the valve cover and intake manifold with new OEM parts.   After the replacement, the crankcase seemed to have a little too much vacuum - probably 4 psi.    So I swapped on a Dorman valve cover and checked that the boost check valve was still in the intake.   Same result - higher than expected crankcase vacuum.   

Cooling fan needed to be replaced as the resistor was fried and the fan wouldn't run at any speed.   The bumper needs to come off to do that job, making it easy to inspect the intercooler input/output pipe connections.   Could tell that some oil had gotten into the intercooler and leaked past the o-rings and leaving some residual oil around the connection.   Removed and cleaned the connection on the output side, will conduct a pressure test to see if the seals are leaking at 15-20psi. 

The MAF sensor had been showing about 1.8 g/s at warm idle, and the car has poor idle with the AC compressor clutch energized. 

Hypothesis: The intercooler isn't free flowing enough and causing the engine to pull a higher than designed vacuum through the PCV system.  Test: Pull the intake pipe off the throttle body and check to see if the crankcase pressure decreases to normal <18 inches of water.

Does the hypothesis/test sound plausible? 

 

Does the hypothesis/test sound plausible? 

Honestly? No, I don't think so. But I'm wrong all the time! I'd be genuinely interested to see how this goes if you do the test.

For me, your charge air cooler has to be severely restricted in order to cause an increase in intake vacuum and impact PCV function. Restricted, like, the car won't make it out of the parking spot. Completely caved in. I've seen those charge air coolers leak a few times, but never restrict.

Plus, your MAF reading of 1.8 g/s sounds entirely reasonable for this engine. You can also compare the MAF rate with the Calculated Air Flow for reference. They should agree within .5 g/s.

Another test would be to monitor Absolute Load and the boost pressure sensor during a WOT run through 2nd gear. Healthy LUV/LUJ engines will clear 175% Absolute Load. A restricted cooler would lead to low Absolute Load and low boost (or vacuum) at the boost pressure sensor.

Just remembered, you've got a data log!

 

Absolute Load only goes to 150%-ish, but you may not have been standing on the gas, either. MAP was reading a decent 25 PSI. I don't think you'd see those kind of numbers with a restricted charge air cooler.