Idle only engine misfires?

DJ001

MEMBER
2017 MAZDA 6
2.5L
4 CYL
2WD
AUTOMATIC
115,000 MILES

Hi, my car has idle only misfires on cylinder four mainly and to a less degree on cylinder two. There is no CEL. The mechanic has tested for vacuum leaks and compression and there seems to be no issue there. Spark Plugs and coils were changed, and the issue has not been resolved. Keen to hear your thoughts. Is it possible to swap injectors around to troubleshoot possible injector issue on a DI engine?

Thursday, September 15th, 2022 AT 3:14 PM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
51,582 POSTS

Yep, I would replace the #4 injector, it must be getting clogged which alters the spray pattern which is most noticeable at idle. Here is how to change the injector out in the images below. Please go over all service precautions before you begin, (last three images). Check out the images (below). Please let us know what you find. We are interested to see what it is.

Images (Click to make bigger)

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Friday, September 16th, 2022 AT 10:53 AM

DJ001

MEMBER
2 POSTS

Thanks for your response. It's just that I got a mechanic to move the injector from 4 to 3 and the misfire did not follow, so wondering if it is actually the injector at fault.

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Sunday, September 25th, 2022 AT 4:26 PM

KEN L

MASTER CERTIFIED MECHANIC
51,582 POSTS

The injector seems to be okay then. That just leaves the coil and spark plug, I would replace both in case there is a defective unit which happens. Also we should do a compression test on #4 this guide will show you how.

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over this guide and report back.

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Monday, September 26th, 2022 AT 11:25 AM