Need help - '14 CX-5 rough engine idle after replacing spark plugs

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2014 Mazda CX-5
Quick update. I took the car for about a little over 6 mile drive on straight roads, some with speed bumps, and up and down hills, and the car ran decent with no dash lights popping up.

I've noticed that the stuttering/hesitation only happens at low RPM/speed, and once it gets higher, then the stutter/hesitation seems to disappear for the most part. The stutter, although still there, doesn't seem as bad once the engine is warmed up.

This also reminded me to check the engine air filter and that definitely needs to be replaced, so have one on the way.

I think next step is to try and replace the coil packs to see if that does anything..

Let me know your thoughts, appreciate the guidance so far 👌
 
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2014 mazda cx-5 touring FWD
Symptoms of a vacuum leak include rough idle and poor low speed performance where those symptoms then lessen or disappear at increased RPMs.
 

AVC

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'17 CX-5 Select
Jmaz has a good point; do a good visual for any vacuum hoses that may have come loose, are cracked. Also carefully check air box to throttle body duct for cracks. As for plug coil, I hate when anyone shoots the parts cannon at a problem. I'd take my clues from any misfire data and either swap that coil with another cylinder and see if the misfire follows, or replace the one coil.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
Quick update. I took the car for about a little over 6 mile drive on straight roads, some with speed bumps, and up and down hills, and the car ran decent with no dash lights popping up.

I've noticed that the stuttering/hesitation only happens at low RPM/speed, and once it gets higher, then the stutter/hesitation seems to disappear for the most part. The stutter, although still there, doesn't seem as bad once the engine is warmed up.

This also reminded me to check the engine air filter and that definitely needs to be replaced, so have one on the way.

I think next step is to try and replace the coil packs to see if that does anything..

Let me know your thoughts, appreciate the guidance so far 👌
I agree with Jmaz and AVC, if you haven’t got any misfire codes after some drives, I’d believe your spark plugs and ignition coil packs should be fine. Something else went wrong and it apparently is not easy to get registered by sensors used to detect abnormal operating conditions.
 
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GA prior 16 CX5 GT
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20 CX5 GT + Prem
Listen under the hood while idling. Sometime you can hear a vacuum leak. Since you did not have a torque wrench and was concerned you put the plugs in too tight, you may have stripped some threads in the soft aluminum head or and are getting a leak around the plug which would be worse at idle...
 
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2014 Mazda CX-5
Quick update:

Checked for vacuum leaks, and found nothing. So continued with replacing parts.

I checked with a scanner again, and there were still no stored or pending ODBII codes coming up.

New coil packs came in and i replaced them all, not just Cyl 4 since i figured im at 120k and if one went they all may go since they did have similar wear marks/patterns.

After replacing them all, the CX-5 is back to purring as normal. Seems like even though no dash lights or codes were being thrown, the coil pack(s) was still an issue. After replacing, everything is back to normal.

Thanks for the assist guys. 👌
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
Quick update:

Checked for vacuum leaks, and found nothing. So continued with replacing parts.

I checked with a scanner again, and there were still no stored or pending ODBII codes coming up.

New coil packs came in and i replaced them all, not just Cyl 4 since i figured im at 120k and if one went they all may go since they did have similar wear marks/patterns.

After replacing them all, the CX-5 is back to purring as normal. Seems like even though no dash lights or codes were being thrown, the coil pack(s) was still an issue. After replacing, everything is back to normal.

Thanks for the assist guys. 👌
Did you get OEM ignition coil packs, or aftermarket ones? IMO ignition coil pack is not considered as a wear-and-tear item. Usually people won’t replace it unless an error code been generated. Even that, only the one indicated by the error code needs to be replaced, not all of them at the same time. Ignition coil pack, especially the OEM one, is not cheap.

Glad you eventually resolved the issue and thanks for the update.
 
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