General Engine Diagnosis Flashcards
A - one of the first steps in diagnosing a drivability complaint is to verify the driver’s complaint.
B - one of the first steps in diagnosing a drivability complaint is to perform a thorough visual inspection.
both correct
When diagnosing drivability complaints, the first step is to verify the driver’s complaint. Sometimes problems can be solved by performing a visual inspection. Cracked vacuum hoses wiring problems and leaks can often be found with a visual check.
A - the first step of any diagnostic procedure is to check DTCs.
B - the search for TSBs should be consulted before any repairs are made.
A - incorrect. First step is to verify complaint.
B - correct.
All of the following are part of the diagnosis process except: A - verify the complaint B - road test C - visual inspection D - reflash the PCM
D - reflash the PCM
Which is the very first step a technician should take when performing a diagnostic procedure? A - perform simple tests B - retrieve DTCs C - check for TSBs D - verify the customer’s complaint
D - verify the customer’s complaint
A - cranking the engine with the throttle fully depressed will force a lean mixture to clear a flooded engine on some vehicles.B - high system voltage will increase fuel injector pulse width
A - correct. Depressing the throttle fully will make the computer enter clear flood mode.B - incorrect. Low system voltage will cause battery voltage correction from the computer which will increase injector pulse width to compensate for the slow opening of the injector.
When diagnosing a fuel injection system problem, a TSB search is performed for all the following reasons except:a - year, make, and VINb - midyear production changesc - service manual updatedd - view revisions to existing procedures
a - year, make, and VIN should be known without a TSB search.
TSBs should be used for all the following except:a - updated service manual proceduresb - updated repair procedures for certain complaintsc - updated vehicle recallsd - updated flash programming
c - updated vehicle recalls. A TSB is not issued for a recall. Vehicle recalls are separately issued.
A - a stethoscope can be used to pinpoint engine noises.B - you may use a long screwdriver for noise diagnosis if a stethoscope is not available.
both correct
Which of the following is not a cause of a noisy valve train?A - high oil pressureB - collapsed lifterC - incorrect valve adjustmentD - bent pushrod
A - incorrect. Low oil pressure can cause valve train noise.B - correct. A collapsed lifter would cause a noise similar to the sound of an ink pen clicking.C - correct. Incorrect valve adjustment will cause noise if the valves are adjusted too loosely.D - correct. A bent pushrod will cause valve train noise because of the extra clearance the bent pushrod causes.
Which of the following is most likely to cause a double knocking noise with the engine at idle?a - excessive main bearing thrust clearanceb - worn main bearingc - worn piston wrist pinsd - excessive rod bearing clearance
c - Worn piston wrist pins cause a double knock because the piston changes direction at TDC and BDC every crankshaft revolution.a - Excessive main bearing thrust clearance will cause the crankshaft to have excessive endplay.b - Worn main bearings will cause a deep low-end knock at idle and at startup.d - Excessive rod bearing clearance will cause a knock that is noticeable on acceleration.
A - Worn valve train components usually produce a clicking noise.B - Engine noise diagnosis should be performed before doing engine repair work.
A - correct. A clicking is usually in the valve train. A double knocking is usually a piston wrist pin. A low knock on startup is usually a main bearing. A knock on acceleration is usually a rod bearing.B - correct.
A - An overfilled crankcase can cause hydraulic lifter noise due to oil aeration.B - Using motor oil with too low a viscosity can cause hydraulic lifter noise.
both correct
A 6 cylinder engine is making a loud metallic knocking that gets louder as the engine warms up or if the throttle is snapped open. The noise almost disappears when the spark to cylinder 2 is shorted to ground.A - The problem could be a cracked flexplate.B - The problem is most likely a loose connecting rod bearing.
A - incorrect.B - correct. If a knock gets quieter when a cylinder is shorted, then the rod bearing is the most likely cause.
A vehicle with double overhead valves is being diagnosed for backfiring through the exhaust manifold.A - This engine uses a separate camshaft for the intake and exhaust valves.B - A 4 cylinder DOHC engine has two camshafts.
A - correct. An engine with double overhead valves will have a camshaft for the intake valves and a camshaft for the exhaust valves.B - correct. A 4 cylinder engine will have two camshafts. A V6 DOHC will have four camshafts.
A - blue smoke in the exhaust indicates oil being burned in the combustion chamber.B - white smoke in the exhaust indicates a rich mixture.
A - correct.B - incorrect. White smoke is an indication of coolant in the exhaust. A vehicle running too rich will have black exhaust.
Which of the following is the most likely cause of blue exhaust smoke?a - worn piston ringsb - worn piston pinsc - rich fuel mixturesd - internal coolant leak
a - worn piston rings. Worn rings allow oil to leak into the combustion chamber where it burns, developing blue exhaust smoke.b - incorrect. Worn piston pins would cause a knock.c - incorrect. A rich mixture would cause black smoke.d - incorrect. An internal coolant leak would cause white smoke.
A vacuum gauge is connected to the intake manifold and the engine is accelerated and held at a steady speed. If the vacuum drops slowly to a low reading then which of the following is the most likely cause.A - a rich fuel mixtureB - over-advanced ignition timingC - sticking valvesD - restricted exhaust
A - incorrect. A rich mixture would cause black exhaust, not vacuum to drop.B - incorrect. Advanced timing would cause a spark knock, not vacuum to drop.C - incorrect. Sticking valves would cause the vacuum needle to flutter.D - correct.
A vacuum gauge indicates 12 inHG. A - Late valve timing will cause a low vacuum reading.B - The gauge should be connected to a venturi vacuum port.
A - correct. Late valve timing will cause the valves to open and close at the wrong time, causing low vacuum.B - incorrect. The vacuum gauge should be attached to manifold vacuum.
During a vacuum test the gauge shows a rapidly fluctuating motion from 15 - 21 inHg at idle. A - This could be caused by a loose intake manifold.B - This could be caused by a burned exhaust valve.
A - incorrect. A loose intake manifold would cause a steady low vacuum reading.B - correct. A burnt valve would cause the vacuum to drop some.
A restricted exhaust will cause vacuum readings to do what?a - 2-3 inHg higherb - 2-3 inHg lowerc - gradually drop as engine speed is increasedd - fluctuate between 17-20 inHG
c - gradually drop.a - incorrect. A high reading is good.b - incorrect. Suspect slight vacuum leak or ignition timing.d - incorrect. Suspect a burnt valve or broken valve spring.
A cylinder power balance test on a distributor ignition vehicle can indicate all of the following except:a - burnt valveb - cracked pistonc - blown head gasketd - weak ignition coil
d - A weak coil would affect all of the cylinders.
During a cylinder power balance test, there is no RPM drop on cylinder 4.A - The cylinder is not contributing to the power flow of the engine.B - The cylinder may have an inoperable spark plug.
both correct
A - During a compression test, low readings on adjacent cylinders may be caused by a cracked cylinder head.B - A low reading on a single cylinder that increases when oil is added is probably a valve problem.
a - correct. A head gasket or cracked head should be suspected.b - incorrect. A low reading that increases with oil is a ring / cylinder problem.
A - running compression should be half of static compression at idle.B - During a running test, the technician should increase the engine speed to 2000 rpm and the value should be less than at idle.
both correct
