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2007 Chevrolet Silverado 4.8L V8 P0301 Misfire: Intermittent Check Engine Light After Plug and Coil Pack Replacement

Model: Chevy Silverado Fault Code: P0301 Posted: 2019-05-19 17:34

The check engine light has come on with a persistent P0301 diagnostic code on my 2007 Chevrolet Silverado 4.8L V8. I have already replaced the spark plugs and ignition wires, and after clearing the codes, the P0301 fault returns consistently. Attached are freeze frame data screenshots from when the code was triggered. Based on these readings, can anyone identify a likely root cause? Page 2 of 4: [Image link - 1.28 MiB] (Viewed 2098 times) Page 3 of 4: [Image link - 1.26 MiB] (Viewed 2098 times) Page 4 of 4: [Image link - 1.33 MiB] (Viewed 2098 times) The misfire appears intermittent — it occurs at idle more frequently than under load, and sometimes the light comes on in the morning, then may go off for hours or even a full day before returning. I have replaced the coil pack, but the issue persists. I do not hear any noticeable engine hesitation or loss of power during operation. The misfire seems to be most evident when the engine is cold.

Related fault codes
P0301
Comments (8)
Anonymous 2019-05-19 18:35

What year and engine size? Do you have access to a misfire counter (current or history)? Are you experiencing any noticeable misfires, especially at idle or under load?

Anonymous 2019-05-20 16:17

This is a 2007 Silverado with the 4.8L V8 engine. I don’t have access to a misfire counter. The issue is intermittent — it happens sometimes at idle, not consistently under load.

Anonymous 2019-05-21 19:25

A clogged fuel injector could be the culprit. Try adding Techtron Total System Fuel Cleaner to half of the fuel tank. How often does the misfire occur? Does the check engine light flash? Could a vacuum leak near cylinder one be contributing?

Anonymous 2019-05-22 18:57

The code typically appears in the morning, may go off by evening, and then returns after a day or two. It does not flash. The coil pack has already been replaced.

Anonymous 2019-05-22 18:59

It seems the misfire is most noticeable when the engine is at idle.

Anonymous 2019-05-22 20:23

Without proper diagnostic tools, any diagnosis remains speculative. Try adding Techtron Total Fuel System Cleaner to half a tank of fuel and monitor performance. A vacuum leak near cylinder one should also be considered. You can perform a simple test by spraying water around the intake gasket area and listening for changes in engine RPM.

Anonymous 2019-05-23 20:00

Regarding a vacuum leak — wouldn't that typically cause a constant misfire rather than an intermittent one?

Anonymous 2019-05-24 06:38

Most misfires occur during cold engine starts and diminish as the engine warms up.