Idle fluctuations

40oz · Aug 10, 2017

I recently added MBRP cat back (no resonator) and AFE air intake. (I will add pics soon) Since that time my idle will act up a little. While at a traffic light it will bounce around dipping down to 600 then up to almost 1000. Also when pulling into my driveway, i left off the throttle but it increased in RPM. Also, the downshift. Not sure if it did it before and I didn't notice, but it does it for sure now and I notice. Not sure if the two are related.

I also recently changed spark plugs.

Any ideas what is causing this? I ordered a tuner from 5 star but have not yet received my custom tunes. Hoping this will fix, but wanted to see what FRF community input was.

Thanks,

waddellw · Aug 10, 2017

40oz said:
I recently added MBRP cat back (no resonator) and AFE air intake. (I will add pics soon) Since that time my idle will act up a little. While at a traffic light it will bounce around dipping down to 600 then up to almost 1000. Also when pulling into my driveway, i left off the throttle but it increased in RPM. Also, the downshift. Not sure if it did it before and I didn't notice, but it does it for sure now and I notice. Not sure if the two are related.

I also recently changed spark plugs.

Any ideas what is causing this? I ordered a tuner from 5 star but have not yet received my custom tunes. Hoping this will fix, but wanted to see what FRF community input was.

Thanks,

Did you remount the MAF perfectly? Those can be quite tricky. It could possibly be the source of your strange idle, but most likely the truck is sorting out the new parts. I'd suggest checking the MAF and disconnecting the battery cable for 10 minutes or so, which should cause the truck to "relearn" certain parameters. This will in theory do what the tune would do to solve this issue as the tune makes the system relearn also.

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40oz · Aug 10, 2017

waddellw said:
Did you remount the MAF perfectly? Those can be quite tricky. It could possibly be the source of your strange idle, but most likely the truck is sorting out the new parts. I'd suggest checking the MAF and disconnecting the battery cable for 10 minutes or so, which should cause the truck to "relearn" certain parameters. This will in theory do what the tune would do to solve this issue as the tune makes the system relearn also.

Sent from my Pixel XL using Tapatalk

I will give that a try. I did not disconnect the MAF just removed the two screws and made the swap. I took my time and did not touch the actual MAF while changing just the base.

LXCoupe · Aug 10, 2017

I had the same problem on my ecoboost F150. Do as waddellw mentioned. Disconnect the battery (I did it over night). Start it up and let it idle for about 10 minutes. It'll idle rough at first but eventually even out. It might also drive erratic too after this, because you also cleared the fuel map for driving. It should level out after a couple minutes of normal driving.

40oz · Aug 11, 2017

Update - Received my tunes from 5 star tuning and uploaded to truck. The first ride after that was a little shaky, but today on the way to work it seemed better. Then drove again to run some errands and seems to be clearing up. Still have a high idle and slow to return to 600 when approaching a stoplight but will continue to monitor. Thanks for the feedback.

Idle fluctuations

40oz

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waddellw

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40oz

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LXCoupe

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40oz

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