Studder under load, P0301 Code

Hi all, could use some help. 2006 Mazdaspeed 6, air intake upgrade, Cobb stage 1 tune.

Yesterday, the car started stuttering under load and threw a P0301 code. As the car warmed up, it got better, but still a noticeable studder on easy acceleration. Spark plugs had 90,000 miles on them, so changed those first, but did not solve my problem. The pulled spark plugs looked good, cylinder 1 maybe had slightly more build up than the other 3 but nothing out of the ordinary

I've swapped coil pack 1 and 4 as the next test, but wanted to upload my accessport logs to see if the experts see anything here. I kept it easy, but there was noticeable studder around the 2000k rpm range.

Any thoughts? If I get an error code on cylinder 4 now, do I need to stick with oem coil packs, or can I go aftermarket?

Thanks!

 

Only use OEM coil packs. What is the spark plug gap set to

 

Thanks for the reply.
I'll check gap, they are NGK plugs. What should the gap be?

Also, a quick update, a swapped coil packs on cylinder 1 and 4, and I am still getting a P0301 code after a few days of easy driving.

 

0.027
Did you not check the gap prior to installation

 

yes, all gapped to .027 or .028

 

Check the wiring to the coil packs

 

great suggestion. Most of the wire is covered by shielding. Anything specific I should be looking for?

In image, left is coil pack for cylinder 1, right is coil pack for cylinder 2.

 

Check continuity through the harness look for damage make sure the pins are making contact

 

thanks, I’ll do that this weekend.

also, I ran a compression test and got consistent results back across all 4 cylinders. ~138psi dry and ~150psi wet for all 4. There was maybe a 2psi variance.

 

Providing an update, the injector for cylinder 1 is bad. Replaced with CorkSport injectors and seals and the car is running good now.

 

Thank you for the update/feedback on your fix.
Please think about a custom tune. You will never think the money was a waste after the results.