rs varies between 0 REVIEW QUESTIONS 1. List four service precautions for workin
ID: 2088788 • Letter: R
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rs varies between 0 REVIEW QUESTIONS 1. List four service precautions for working on the fuel 2. What is indicated by a LTFT reading of 24 percent? 3. What is the correct procedure for checking an oxygen ally high, the air-fuel y be contaminated tinually low, the air. may be defective, or ay be dos the computer may injection system. ains in a mid-range pen loop or the sen- sensor with a DMM pen loop or thesen4. What is the difference between STFI and LTFT? en in the opposite onitored on a scan 5. The PCM checks for a dosed throttle plate each time the engine starts. This becomes the base for all throt- tle settings and can be viewed by looking at the PID with the throttle closed. Which ofthe following would not cause an abnormal reading and a higher-than- ses hard starts on o-start on single- normal idle speed? a. A bad TP sensor b. A bad IAC valve en causes a loss of aw fuel dribbling c Loose or worn throttle plates d. Excessive noise in the TP or related circuits son the tip of6. Which of the following is a likely cause of a lean con el sprayed by the lly sealing, allow- dition during acceleration and cruising speeds? a. A defective oxygen sensor b. A defective PCM king fuel pressure is ruptured, fuel , causing a rich c. A defective ECT sensor d. A defective MAF sensor 7. What problem may result from dirt buildup on an engines throttle plates? e cause of a lean eceiving a sig 8. Which of the following would not cause a hard-to- receiving a signal tor using a high- start problem on a PFI engine? a. A defective IAC valve b. A defective oxygen sensor c. A leaking fuel pressure regulator d. Dirty injectors njector I help isolate a c. A leaking fuel presure regulatorExplanation / Answer
1. a. jump starting is not recommeded
b. Don't disconnect or connect ECU to ignition during testing
c. Double check all other systems and make sure it is working fine
d. Check the manual thoroughly before performing service.
2. LTFT stands for long term fuel trim which represents a percentage of slower adjustment of the injector pulse width over a long term. The fuel delivery to engine is controlled by this value. A value of 24 suggests 24% increase in fuel delivery through the long term analysis by the LTFT units. It is recommended to service the engine at this time this value is abnormal and caused due to some issues.
4. STFT stands for short term fuel trim and LTFT stands for long term fuel trim . STFT is the immediate trimming or adding fuel based on different factors.hence it's adjustment is fast. LTFT is a long term adjustment of fuel from the details gathered from STFT. Therefore the adjustment is very slow and innocent a lot of data analysis.
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