Misfire on 3 and 7 2003 5.3 almost 300k

[Doubeleive]

if cleaning the maf made at least some difference for a bit maybe it needs to be replaced, those things cause a lot of different problems when they go bad, typically around 160k is when they start taking a dump

 

[Hutch123]

if cleaning the maf made at least some difference for a bit maybe it needs to be replaced, those things cause a lot of different problems when they go bad, typically around 160k is when they start taking a dump

I was thinking the same thing. I didnt realize they typically go at 160k by those I should be swapping out my second one for my 3rd lol. I'm gonna give that a shit this week. It really did make a difference cleaning. The truck certainly doesnt hesitate as long as it isnt misfiring. Overall it's more zippy that for sure. I'll replace that MAF and repost this week.

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[Hutch123]

I was thinking the same thing. I didnt realize they typically go at 160k by those I should be swapping out my second one for my 3rd lol. I'm gonna give that a shit this week. It really did make a difference cleaning. The truck certainly doesnt hesitate as long as it isnt misfiring. Overall it's more zippy that for sure. I'll replace that MAF and repost this week.

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Whoops I meant shot lol*

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[Hutch123]

Well I forgot to update after replacing the MAFS. It didnt seem to fix the truck at first. Then about 500 miles later all of sudden no more misfire. I'm scratching my head. I'm waiting for it to show back up.

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[retiredsparky]

Hutch, you mentioned early in this thread that you had pulsing interior lights and a code related to throttle position sensor.

How old is your battery? Have you had it load checked? Have you had the alternator checked for a diode failure? Both of those things can cause many different symptoms. And they can vary and/or go away intermittently. A diode failure will introduce alternating current or pulsing current into the power supplies of all the modules/pcm/ etc. in the truck. Pulsing lights can be an indicator of this type of failure. The diode can start to fail, then "heal" itself temporarily.

I have fixed GM vehicles with crazy symptoms by changing the battery, also. The power supplies in all the electronics do not like anything except 12-15 volts D.C.(Plus or minus) Anything else is bad news. Even though an engine will start, that does not indicate that the battery is good.

If you continue to see throttle position codes intermittently, you should consider replacing it with a used one from a junkyard if you want to go cheap, just to see if the symptoms go away. That sensor is very important to the running of the truck. Any confusion of the signals from that sensor can send the engine into a limp mode temporally.
And finally, codes don't necessarily get set for every intermittent problem in vehicles.

 

[Hutch123]

Hutch, you mentioned early in this thread that you had pulsing interior lights and a code related to throttle position sensor.

How old is your battery? Have you had it load checked? Have you had the alternator checked for a diode failure? Both of those things can cause many different symptoms. And they can vary and/or go away intermittently. A diode failure will introduce alternating current or pulsing current into the power supplies of all the modules/pcm/ etc. in the truck. Pulsing lights can be an indicator of this type of failure. The diode can start to fail, then "heal" itself temporarily.

I have fixed GM vehicles with crazy symptoms by changing the battery, also. The power supplies in all the electronics do not like anything except 12-15 volts D.C.(Plus or minus) Anything else is bad news. Even though an engine will start, that does not indicate that the battery is good.

If you continue to see throttle position codes intermittently, you should consider replacing it with a used one from a junkyard if you want to go cheap, just to see if the symptoms go away. That sensor is very important to the running of the truck. Any confusion of the signals from that sensor can send the engine into a limp mode temporally.
And finally, codes don't necessarily get set for every intermittent problem in vehicles.

The battery and alternator have both been replaced during the time of the pulsing lights and TPS issue. However I think I'll get them checked just to be sure. Yesterday this tps code starting throwing more frequently. Like 10 times in an 80 mile drive instead of once or twice a week. You never know. I'm gonna look around for the TPS at my local LKQ. Will update.

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[Fleetgeo]

How are the intake manifold gaskets on the truck . I had a buddy with a z71 tahoe 2004 flex fuel and he had a random misfire code that would come and go. Someday it starts pretty smooth then idle out and become a little rough but i believe he had some similar problems to yours. He replaced the intake gaskets and his truck was running like new .

 

[Hutch123]

How are the intake manifold gaskets on the truck . I had a buddy with a z71 tahoe 2004 flex fuel and he had a random misfire code that would come and go. Someday it starts pretty smooth then idle out and become a little rough but i believe he had some similar problems to yours. He replaced the intake gaskets and his truck was running like new .

Shop that looked at it said there was no leak around the intake manifold. I had also sprayed carb cleaner around them and it didnt rev up or anything. That's a common issue I had read about in the beginning.

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[Hutch123]

First, I'd like to apologize for leaving everyone hanging on this thread. I've been swamped and everything else I own from HVAC, Mower, generators, trimmers, chainsaw, etc. Decided to take a dump every time I went to use them. My work week can be 96 hours sometimes. (Saving up for a remodel) I'm catching up and hopefully this weekend I'm going to be able to spend some time further troubleshooting this thing. Second I have a couple of new findings/info. The alternator is putting out 14.25-14.5 when running, consistantly, I havent seen any dips or spikes. Another thing I've noticed is the truck runs much better when it's cold out. It wont misfire until the truck warms up for a long while or the temperature outside warms up. Another odd thing I noticed is the truck either misfires OR it throws the P1516 code and goes into LPM. Never does it misfire and throw the P1516. I'm going to try the carb cleaner spray test again this weekend, maybe the gaskets are getting warm and then leaking?
**edit** I also have replaced the battery with a Red Top Optima. The old battery WAS bad. Still having the flickering interior lights, this happens with or without the engine running. God what a mess lol

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[Sam Harris]

First, I'd like to apologize for leaving everyone hanging on this thread. I've been swamped and everything else I own from HVAC, Mower, generators, trimmers, chainsaw, etc. Decided to take a dump every time I went to use them. My work week can be 96 hours sometimes. (Saving up for a remodel) I'm catching up and hopefully this weekend I'm going to be able to spend some time further troubleshooting this thing. Second I have a couple of new findings/info. The alternator is putting out 14.25-14.5 when running, consistantly, I havent seen any dips or spikes. Another thing I've noticed is the truck runs much better when it's cold out. It wont misfire until the truck warms up for a long while or the temperature outside warms up. Another odd thing I noticed is the truck either misfires OR it throws the P1516 code and goes into LPM. Never does it misfire and throw the P1516. I'm going to try the carb cleaner spray test again this weekend, maybe the gaskets are getting warm and then leaking?

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Good luck brother. I know how it is when you’re busy as hell, and have to fix / repair everything you need to get your work done! Frustrating! Sorry I can’t really help with the diagnosis.