Last month we asked this Tech question and invited you to share your answer. We value your expertise and want to thank everyone who participated!
Question: While performing an exhaust backpressure test on a 2.0L four-cylinder engine, the technician notices that the needle of the gauge is fluctuating between 0 psi and .3psi at idle but is fairly steady at .4 psi while holding the engine to 2500rpm. What does this indicate?
Answer: Normal condition. During an exhaust backpressure test a gauge is installed in front of the catalytic convert to determine if there is a restriction behind this point. There is only one cylinder at a time on the exhaust stroke. As each cylinder pushes its exhaust out there is a fluctuation in the gauge. Because there is 180 degrees of crankshaft rotation between each cylinder’s exhaust stroke the needle of the gauge will fluctuate more at idle than at 2500 rpm where the exhaust strokes are happening faster.
Congratulations to the following shop who answered this question and will be receiving a prize pack!
- Mike at Elford Automotive. in St Thomas, ON
The Tech Challenge question is published in our weekly eNewsletter with an online answer form. Fill out the form with the details of how you would perform the repair to be entered for the chance to win the prize pack. You can also submit a challenge for future Tech Challenges! A draw is conducted with all shops who answered the question correctly and one is selected as a winner for a prize pack.
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