The Dreaded P0300 Code: Solved

[Fless]

Those old plugs do look worn. What part number are they?

 

[tooleyondeck]

Those old plugs do look worn. What part number are they?

Old plugs are PN: 12567759

The summit plug wires I ordered were significantly shorter than OEM, despite their site saying that they fit. I test fitted one and it technically fit, but it was stretched tight and I didn’t like it.



I dropped them off for return today and I just picked up some Duralasts from the local parts house. If they end up being duds I’ll order some OEMs. New plugs are AC Delco 19307137 platinum tip. Gapping and installing them now.

 

[tooleyondeck]

Got the new plugs and wires in and took it for a test drive, fired right up and runs great. Data log looked good on about a 15min drive, did a couple of pulls onto the highway and no hiccups. P0300 can be a problematic code as we all know, thankfully this time it was the simplest scenario.



While removing the coils and dipstick on the passenger side, I found a small coolant leak from the rear A/C heater hose connector, so I went ahead and replaced that too.

 

[Gearz]

Yes there are 2 different spark plug wires depending on which coil packs you have and that's why you always go to the GM website and do a search and it will give you that information. It's not easy sometimes finding the correct parts. ( BEN THERE DONE THAT ) LOL

 

[mcorbitt52]

I wish I was so lucky to find a similar solution. My 2003 Tahoe (LT 5.3 V8) has had an intermittent misfire condition for nearly 5 years. I've been to multiple repair shops and I have replaced the following based on their "expert" diagnosis:
- spark plugs
- spark plug wires
- coils
- MAF
- TB
The misfires occur intermittently, but more often on a cold start. Sometimes I go weeks without an issue. On a few occasions I have had a misfire crop up while highway driving (however in these cases the misfire lasts only a few minutes).

What I have learned, is when the engine reaches normal operating temperature (approx. 208 degrees) and a misfire occurs, if I turn the engine off for about 30 seconds, it will always correct the misfire and run like a beauty.

I would appreciate any thoughts of wisdom on what some of you think could be the solution.

Mike

 

[tooleyondeck]

I wish I was so lucky to find a similar solution. My 2003 Tahoe (LT 5.3 V8) has had an intermittent misfire condition for nearly 5 years. I've been to multiple repair shops and I have replaced the following based on their "expert" diagnosis:
- spark plugs
- spark plug wires
- coils
- MAF
- TB
The misfires occur intermittently, but more often on a cold start. Sometimes I go weeks without an issue. On a few occasions I have had a misfire crop up while highway driving (however in these cases the misfire lasts only a few minutes).

What I have learned, is when the engine reaches normal operating temperature (approx. 208 degrees) and a misfire occurs, if I turn the engine off for about 30 seconds, it will always correct the misfire and run like a beauty.

I would appreciate any thoughts of wisdom on what some of you think could be the solution.

Mike

Well, If you've eliminated the parts mentioned as being culprits, I would check your intake manifold gasket next. If it happens most often on cold starts, the gasket may not be fully sealing until it warms up. I would also check your injectors and test your coil pack wiring harness for any shorts. There are a lot of things that can cause a random misfire code.