Service Repair

Solved: A rough running Ford Escape

Feb. 12, 2025

A shop was facing a 2018 Ford Escape with a turbo-charged, four-cylinder engine. The vehicle suffered from a poor idle concern, intermittent cylinder No. 3 misfire at idle, but no DTCs stored.

Brandon Steckler

The rounded exhaust valve pocket and elevated intake manifold pressure come together like puzzle pieces inferring excessive valve overlap. Due to this valvetrain’s configuration, valve clearances are adjusted by way of selectable shims. The appropriate shim was chosen, and the clearances were brought back to within specification. The driveability symptom vanished, expected manifold vacuum was restored, and the fuel trim values nearly zeroed.

I was providing technical support to a shop facing a 2018 Ford Escape with a turbo-charged, four-cylinder engine. The vehicle suffered from a poor idle concern, intermittent cylinder No. 3 misfire at idle, but no DTCs stored.

Get caught up on the vehicle specifics.

What would you recommend doing next, given the data bullet points in last month’s challenge?     

Inspect valve lash.
Decarbonize induction system.
Treat crankcase for stuck piston rings.
Replace camshafts for decoupled CMP reluctors.

For those of you who chose answer No. 1, congratulations! The valve clearances were measured, and several of them (including cylinder No. 3 exhaust valve) were found to be too tight, creating the excessive overlap and reducing the manifold vacuum. This led to the speed-density fueling strategy over-fueling the cylinders and was the cause of the negated fuel trim.

The rough running condition was also attributed to the excessive valve overlap as the affective induction stroke of cylinder No. 3 was reduced because the cylinder was drawing in inert exhaust gas (like an EGR-effect).

Answer No. 2 is incorrect. Although a heavily carboned induction system could reduce manifold vacuum, the effected cylinders would tend to experience a worsening symptom with acceleration, as restrictions create pressure drops that intensify with flow.

Answer No. 3 is incorrect as well. Stuck piston rings would reduce manifold vacuum, cause a speed-density fueling strategy to over-deliver, and ultimately drive fuel trim numbers down. However, the relative compression pattern would’ve indicated lower starter load, not the steady 170 Amps that is visible in the capture. Besides, no smoke was exhibited leaving the tailpipe and no other evidence of oil consumption were present.

Answer No. 4 is incorrect as decupled CMP reluctors may allow a CKP/CMP correlation waveform to appear in time, however the in-cylinder pressure waveform capture would’ve demonstrated a shift in cam timing, which is not apparent. The most logical answer is to inspect the valve lash.

About the Author

Brandon Steckler | Technical Editor | Motor Age

Brandon began his career in Northampton County Community College in Bethlehem, Pennsylvania, where he was a student of GM’s Automotive Service Educational program. In 2001, he graduated top of his class and earned the GM Leadership award for his efforts. He later began working as a technician at a Saturn dealership in Reading, Pennsylvania, where he quickly attained Master Technician status. He later transitioned to working with Hondas, where he aggressively worked to attain another Master Technician status.

Always having a passion for a full understanding of system/component functionality, he rapidly earned a reputation for deciphering strange failures at an efficient pace and became known as an information specialist among the staff and peers at the dealership. In search of new challenges, he transitioned away from the dealership and to the independent world, where he specialized in diagnostics and driveability.

Today, he is an instructor with both Carquest Technical Institute and Worldpac Training Institute. Along with beta testing for Automotive Test Solutions, he develops curriculum/submits case studies for educational purposes. Through Steckler Automotive Technical Services, LLC., Brandon also provides telephone and live technical support, as well as private training, for technicians all across the world.

Brandon holds ASE certifications A1-A9 as well as C1 (Service Consultant). He is certified as an Advanced Level Specialist in L1 (Advanced Engine Performance), L2 (Advanced Diesel Engine Performance), L3 (Hybrid/EV Specialist), L4 (ADAS) and xEV-Level 2 (Technician electrical safety).

He contributes weekly to Facebook automotive chat groups, has authored several books and classes, and truly enjoys traveling across the globe to help other technicians attain a level of understanding that will serve them well throughout their careers.