Intermittent misfire at low RPMS

AlphaZulu · Nov 30, 2024

Hello all, I bought a 2017 Tahoe SSV recently with the 5.3L L83 engine. While towing a few months ago I began to get significant misfires and a P0303 code, but only when under load at less than 2,250 RPM. After finishing that trip by keeping the RPMs higher, I changed the oil and on my next trip I got misfires and a P0307 code consistently when under load at below 2,250 RPM.

What would you consider a good starting point for diagnostic? The vehicle has about 91k miles and had the transmission rebuilt at 53k.

Thank you for any assistance.

AlphaZulu · Dec 2, 2024

I guess since no one has any insights I'll just do plugs and wires and see if that helps. I was hoping to avoid the mindless loading of the parts canon, but 91k is probably fairly reasonable for the plugs and wires anyways.

Tahoe14 · Dec 3, 2024

@Doubeleive, @Fless, @OR VietVet

OR VietVet · Dec 3, 2024

Because of the mileage and the known misfires on cylinders #3 and #7, I would say you are on the right track. I would remove all plugs and pay special attention to #3 and #7 and compare to the other plugs. I would replace with new plugs and wires. Post pics here of the plugs, close ups of the firing tips and pinpoint #3 and #7. How do the wires look, too. You likely have no idea how much idle time is on those plugs and wires, since it is an SSV.

https://www.rockauto.com/en/moreinfo.php?pk=13869485&cc=3434402&pt=7212&jsn=956

More Information for GM GENUINE 19431551

Doubeleive · Dec 3, 2024

at 91k add a induction service as well, this will help particularity with the direct injection motors

OR VietVet · Dec 3, 2024

Doubeleive said:
at 91k add a induction service as well, this will help particularity with the direct injection motors

Like cleaning the MAF?

Doubeleive · Dec 3, 2024

OR VietVet said:
Like cleaning the MAF?

well that's part of it but the induction service on the k2's involves cleaning the intake valves as well, carbon build up is a known problem usually shows up as a hesitation when accelerating, rough idle, etc. If it's time to do plugs and wires then it's time to do the service also.
this video shows what happens by 100k

AlphaZulu · Dec 4, 2024

OR VietVet said:
Because of the mileage and the known misfires on cylinders #3 and #7, I would say you are on the right track. I would remove all plugs and pay special attention to #3 and #7 and compare to the other plugs. I would replace with new plugs and wires. Post pics here of the plugs, close ups of the firing tips and pinpoint #3 and #7. How do the wires look, too. You likely have no idea how much idle time is on those plugs and wires, since it is an SSV.

https://www.rockauto.com/en/moreinfo.php?pk=13869485&cc=3434402&pt=7212&jsn=956

More Information for GM GENUINE 19431551

Thank you for the reply. I ordered the plugs and wires and will report back on Saturday after I tackle the job.

AlphaZulu · Dec 7, 2024

Well, I got cylinders 1-7 done, and have enormous respect for anyone that can get #8. Worthy of note is that #7 had an aftermarket plug wire made by Packard with a 90° elbow on the plug end. This pushed the wire up against the exhaust manifold heat shield, and I believe this was the cause of my misfire. After changing (almost) all of the plugs and wires the vehicle runs smooth and strong.

Thanks again for the advice OR VietVet & Doubeleive

Fless · Dec 7, 2024

Hope the new plugs are the same, because the ones you removed are way mismatched. Nos. 1 & 5 were a different heat range than the others.

@Rocket Man shows the tool setup for the #8 plug:

spark plug change 5.3

So i decided to change my plugs on my 2008 Tahoe after a 125,000 miles, the driver side easy to do but the passenger side little more difficult. So i removed the inner wheel well liner and used my dewalt clamp to push the AC lines up to access the rear plug, see pic. Hope this helps someone.

www.tahoeyukonforum.com

Intermittent misfire at low RPMS

AlphaZulu

TYF Newbie

AlphaZulu

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Tahoe14

Full Access Member

OR VietVet

Multnomah Falls

Doubeleive

Wes

OR VietVet

Multnomah Falls

Doubeleive

Wes

AlphaZulu

TYF Newbie

AlphaZulu

TYF Newbie

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Fless

spark plug change 5.3

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