New MAF and O2 both replaced twice

BEE7AVC

MEMBER
2011 MAZDA 3
2.0L
4 CYL
2WD
AUTOMATIC
119,850 MILES

The car had broken down when the MAF sensor stopped working entirely and stopped running. I got a new MAF and it was giving me a lean code but also running rich. So I took it back and got another and the same thing happened again. So I changed the 02 sensor twice as well thinking that part was bad twice smoked out the entire system and sprayed carburetor cleaner no vacuum leak. A/F ratio is reading 9.5:1. Did a test run 0-60 on my diagnostic tool and recognized a weird fuel trim pattern as if I have a vacuum leak but I do not break booster works fine no issues.

5 Replies

BEE7AVC

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4 POSTS

This is the result of the test.

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Wednesday, September 12th, 2018 AT 11:51 AM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

How does the engine run? If the engine is misfiring it will create this problem can we plug the plugs and check their condition? Please upload pictures of the spark plugs which will help as well. Here is a guide to help us get started:

https://www.2carpros.com/articles/how-to-change-spark-plugs

Also lets run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

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Monday, September 17th, 2018 AT 11:52 AM

BEE7AVC

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4 POSTS

Just replaced the MAF again they were giving me the wrong part. It is running better no drop in rpm's when I turn on the A/C the a/f went to 11:1. I will pull the plugs today and send pictures they are a couple months old plugs three prong I think they might need gaped. It tends to run more rich on throttle according to my scanner going to check the air filter too seems restricted should be getting 2g/s only getting 1.8 according to MAF. Sounds like it may have a light misfire it is not as noticeable as if you were to pull the o2 but it definitely has one.

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Monday, September 17th, 2018 AT 1:05 PM

BEE7AVC

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4 POSTS

The codes I have are a p0140 and a p0171.

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Monday, September 17th, 2018 AT 1:16 PM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

Yep, this can be the oxygen sensor or a cylinder misfire. Try replacing the spark plugs first then go for the sensor here are two guides to help you. Does it seem to run okay?

https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please run down these guides and report back.

Cheers, Ken