ASE Practice Test #4 2

Question 1

A vehicle with rack-and-pinion steering has excess play in the steering wheel (more than 2 inches of free play). What is the MOST likely cause?

Accepted Answer

Worn rack-and-pinion internal gear (rack yoke wear), worn tie rod ends, or a loose steering column coupling

Answer

Steering play (free movement of the steering wheel before the front wheels begin to turn) should be minimal. Excess play indicates looseness somewhere in the steering linkage. The most common causes are worn internal rack-and-pinion gear teeth or the rack yoke (which presses the rack against the pinion — a worn yoke spring allows the rack to separate slightly from the pinion), worn outer or inner tie rod ends, or a loose intermediate steering shaft coupling (U-joint or rag joint). All components from the steering wheel to the wheels must be inspected.

Question 2

A technician is replacing the timing chain on an OHC (overhead cam) engine. What critical adjustment must be made before installing the new chain?

Accepted Answer

Set the engine to TDC on cylinder 1 compression stroke and align all camshaft and crankshaft timing marks

Answer

Correct valve timing is essential for engine operation and to prevent valve-to-piston contact (on interference engines). Before removing or installing a timing chain, the engine must be positioned at TDC on cylinder 1's compression stroke (both camshaft lobes for cylinder 1 pointing away from the cam followers). All timing marks on the crankshaft sprocket and camshaft sprocket(s) must be aligned exactly as specified by the OEM before installing the new chain and verifying alignment again after installation.

Question 3

What is the purpose of "brake bias" in vehicle brake system design?

Accepted Answer

To distribute brake force front-to-rear in proportion to weight transfer during braking, ensuring optimal stopping performance without rear wheel lockup

Answer

During braking, vehicle weight transfers forward, increasing front tire load (grip) and reducing rear tire load. If rear brakes receive too much hydraulic pressure relative to the reduced rear tire grip, rear wheels lock up, causing a spin. Brake bias (also called brake proportioning) distributes hydraulic pressure front-to-rear so the front brakes do proportionally more work. This matches braking force to available tire traction on each axle. Proportioning valves and electronic brake force distribution (EBD) implement this bias.

Question 4

A gasoline direct injection (GDI) engine has been diagnosed with excessive carbon deposits on the intake valves. What is the root cause specific to GDI engines?

Accepted Answer

In GDI engines, fuel is injected directly into the cylinder (not the intake port), so there is no fuel washing over the intake valve backsides to clean off oil vapor deposits from PCV and valve stem seals

Answer

Traditional port-injected engines spray fuel directly onto intake valves, and the fuel naturally washes away oil vapor deposits from PCV blow-by and valve stem seal leakage. GDI engines inject fuel directly into the combustion chamber, so the back of the intake valves never gets this fuel wash. Over time, oil vapors from the PCV system coat the intake valves with carbon deposits that build up, restricting airflow and causing rough idle, hesitation, and power loss. Walnut blasting or chemical intake cleaning is the repair.

Question 5

What is the purpose of measuring valve stem-to-guide clearance in a cylinder head rebuild?

Accepted Answer

To ensure the valve stem moves freely without side play that causes oil burning and without so much clearance that the valve rattles or seats improperly

Answer

The valve guide provides a precise bore for the valve stem to travel up and down while sealing the valve stem from combustion chamber gases and engine oil. Insufficient clearance (too tight) causes the valve to stick or seize, especially when hot. Excessive clearance allows the valve stem to rock side-to-side, causing side loading on the seat (improper sealing), excessive oil consumption (oil sucked past valve stem seal), and valve stem wear. Measuring with a dial indicator determines if guides are within spec or need reaming/replacement.