An easy quiz

[jimberg]

Chris, here are my answers and my rationalizations.

1. An EFI system is unable to change the pulse widths of the injectors, which of these could cause the problem?

d. A Defective ECM.

I'm not really sure about what you were asking. If the O2 sensors were 100% bad, the ECM wouldn't be able to adapt by changing the pulse width, but the pulse width would still be changeable based on MAF, BAP, ECT, and ACT readings.

A weak fuel pump or defective FPR would be the cause of a pulse width change, not the limitation.

2. An EFI engine has an irregular idle speed when cold:

Tech A says that the problem could be caused by a bad oxygen sensor.
Tech B says that the problem may be a faulty Idle Air Control (IAC) system.
Who is right?

B. Tech B.

I think the "when cold" is the key here. When the engine is in cold startup, it's using open loop and therefore the O2 sensors aren't active. Even if the O2 sensors were defective and the computer adapted by richening the fuel mix, a rich mixture is good for cold startup conditions.

3. A car equipped with a smog pump system backfires during deceleration, which of these could be the cause of the problem?

a. Defective diverter valve.

This is a tricky question so I'm not sure about the answer, but given the options, only the diverter valve seems to make sense. A bad check valve would allow exhaust to flow backwards into the diverter valve and air pump wich would damage the other components and maybe eventually cause a backfire, but I'm thinking you want the one defective component that would cause such a problem. A bad pump would just not pump air which would be no big deal other than the eventual clogging of the cats.

4. A vehicle hesitates when the throttle is opened quickly, which of these is a possible cause of the problem?

a. Low fuel pump pressure.

5. While inspecting a set of spark plugs, you find one plug that has a badly burned electrode, what is the most likely cause of the problem?

c. Ignition cross firing.

I'm assuming that by burnt, you mean melted. Preignition and cross-firing would cause electrodes to melt.

6. Which of these will NOT cause a tapping noise while the engine is running?

d. A burnt exhaust valve.

The other three options can clearly cause a tapping noise. A burnt exhaust valve may allow for low compression or backfiring because of fuel getting into the exhaust manifold, but it wouldn't really be a tapping noise.

7. When replacing piston rings:

c. use a ball hone to deglaze the bore.

8. All of these will cause low compression readings, EXCEPT:

c. A slightly slipped timing belt.

The other three are obvious causes and a slightly slipped timing belt wouldn't be off timing enough to allow a valve to be open on the compression stroke to reduce compression.

9. Which of these is a true statement about oil pressure?

b. The pressure will be high if the pressure regulator is defective.

Large oil clearances will cause low pressure.
A blockage will raise pressure.
High viscosity means that it is thick oil and, therefore, will flow harder causing the pressure to go up.

10. All of these could be the cause for one power door lock not working, EXCEPT:

b. A defective circuit breaker.

A defective circuit breaker would cause a failure in both locks.



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351W 89 Mustang GT Convertible