2003 Tahoe 5.3 - Random Multiple Cylinder Misfire

[mcorbitt52]

For the past 6 months my 2003 Tahoe 5.3 V8 periodically gets a “random multiple cylinder misfire detected” (P0300 on low-end code reader).

There is no consistency. It goes weeks without surfacing, then can happen on an initial start-up, or after the Tahoe has warmed up and then turned off and restarted. It has never surfaced once the car has started and is running normal.

Usually the rough running clears up after 5-10 minutes. This week it surfaced after the Tahoe had not be run for a few days, and it had been a few weeks before it had run rough. The symptom lasted for a few days on short drives but this morning started and ran fine.

The Tahoe has 163K miles. I have owned it for 3 years but do not know what the past history of service. Recently I changed the sparks plugs (they looked like they were due), and then was planning to change the ignition coils and possibly the pre-converter O2 sensors. I also realize this could be a fuel problem.

If any of you have experienced this same issue and were able to resolve the problem, is there a logical step-by-step I should follow to narrow in on the exact cause of the issue? Given the mileage, is it also about time I change out these parts anyway?

Thanks for any assistance.

 

[Scottydoggs]

could be busted up cats clogging and unclogging. if you bang on them and hear them rattle inside you know they are bad.

 

[Fless]

Have the spark plug wires been changed?

 

[SnowDrifter]

What are your fuel trims and fuel pressure?

Are you using a dry filter or oiled filter? How's the MAF?

What did you gap the plugs to?

 

[Ilikemtb999]

I had this exact same thing on my 01 5.3 that I hunted down for months, turned out it was just a semi clogged injector. Changed it out and was back to normal. Could also be intake manifold gaskets as they’re known to go back if they’re not the updated ones.

 

[Doubeleive]

my exwifes 04 did that, basically ended up shotgunning it plugs, wires, coils and then to top it off a new MAF then it finally went away. It was all of those things combined as I discovered along the way, had a couple bad wires, couple bad coil packs, and a bad MAF. now she purs like a kitten again.

 

[mcorbitt52]

Have the spark plug wires been changed?

Spark plug wires are on the list to be changed this weekend. thanks for the feedback

 

[mcorbitt52]

could be busted up cats clogging and unclogging. if you bang on them and hear them rattle inside you know they are bad.

I had not thought about this. I will check it out. thanks.

 

[Larryjb]

Invest in a scantool. You can get some decent ones for less than $500. This could pay off with just one service visit, as long as you know how to use it properly. If your fuel trims are too high, that means that the computer is trying to add fuel to compensate for extra air that got in without being metered. A dirty MAF could cause this, but also leaking intake manifold gaskets. There are other possible causes for this. Here is a good video showing how a scantool was used to confirm a vacuum leak, and what was leaking:

(common causes of random misfires is also a leaking intake manifold)

Right now you're shooting in the dark with troubleshooting.

 

[tdemontigny91406]

Before you get crazy with everything how many miles? Last time spark plugs were changed? If they were hopefully not Bosch they tend to do that quickly. I'd pull the boot off the fpr (fuel pressure regulator) located on the fuel rail drivers side and see if there's fuel on the outside of the regulator if there is it's a bad regulator causing fueling issues causing it to bounce from cylinder to cylinder just my .02