Vehicle: 2018 Jeep Cherokee, 4WD, L4-2.4L, Automatic Transmission/Transaxle

Mileage: 147,095 miles

Problem: The Jeep Cherokee was brought in for a new head gasket. After the head gasket was replaced, the vehicle started and ran fine, but after idling for about five minutes, it would shut off and not restart until it sat for a few minutes.

Case Details: The technician checked compression by using a compression gauge. When the engine was running well, compression was about 150 psi. When the engine stalled and wouldn’t restart, compression would not go above 60 psi. If the technician reinstalled the spark plugs, the engine would start again, run fine for about five minutes and then die again.

The only diagnostic trouble code (DTC) the technician found was P0303 – #3 Cylinder Misfire, but all the cylinders would intermittently have little to no compression.

This weird problem presented a perfect opportunity to call ALLDATA Tech-Assist. The Tech-Assist consultant asked if the technician had checked the engine oil level. This vehicle has a “multi-air” engine that uses oil pressure to open intake valves. Low engine oil, low oil pressure, incorrect oil grade, or a variable valve actuation assembly (VVAA) solenoid malfunction could cause a compression loss.

The consultant also asked if the technician replaced or verified that the VVAA filter was clean when the cylinder head was off. (see #3 in image A.) In addition, he asked the technician whether he had the special tool to install the VVAA when he put the cylinder head back together.

NOTE: The manufacturer specifies that damage will occur to the VVAA assembly or the cylinder head if the tool is not used. The technician said that he had used the special tool and was careful not to damage the head or the filter.

In that case, the consultant said, the next step would be to test the solenoids (see image B). If the solenoids were not working, that could cause the misfire on cylinder #3 and the low compression issues. The technician went to work removing the head to check the VVAA filter and passageway first.

The Tech-Assist consultant suggested looking at TSB #28 09 05 in ALLDATA. The symptoms closely mirrored what the technician was describing. The TSB said that the DTCs and dying problem could be caused by the spacer installed between the engine speed (RPM) sensor and the gearbox. The fix was to remove the engine speed sensor, discard the spacer and then reinstall the engine speed sensor.

Confirmed Repair: After the technician removed the spacer and reinstalled the engine speed sensor, he cleared the DTCs and took the vehicle for a test drive. The engine ran very well, did not stall and no DTCs returned. Fixed!