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5.3 misfire

This is a discussion on 5.3 misfire within the Technical / Maintenance forums, part of the General Discussion category; 03 silverado 5.3, 74,000 miles. lately when i go to start the truck after its sat awhile and got good ...

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    5.3 misfire


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    03 silverado 5.3, 74,000 miles. lately when i go to start the truck after its sat awhile and got good and cold, it has been sounding like it has a big cam in it. doesnt sound BAD, i wouldnt guess its a miss just listening to it. usually only lasts a minute or so till the motor warms up, then it goes back to sounding normal. today, i start it and the SES light starts flashing, meaning a misfire detected. its making the same sound so i assume its been doing this all along, just hasnt tripped the light. shut the truck off, restarted it, and the light stops flashing. it runs fine, havent noticed any major loss in fuel economy. replaced plugs and wires waiting for it to get cold enough to see if that fixed it. if it doesnt, what should i check next? any problems like this common on these motors?

  2. #2
    Resident Finn
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    Re: 5.3 misfire

    What plugs did you use?

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    Re: 5.3 misfire

    ac delco plugs and wires. wont use anything else in gm vehicles. the problem started before i replaced the plugs and wires, ill start it in the morning and see if that fixed it

  4. #4
    Resident Finn
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    Re: 5.3 misfire

    OK. I just went through a misfire thing with mine when using other than AC Delcos or NGKs. Hence the question.

    Hope you find a solution soon.

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    Re: 5.3 misfire

    check intake for leaks.mainly left bank front cylinders. very common problem.

  6. #6
    Resident Finn
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    Re: 5.3 misfire

    OK. I just went through a misfire thing with mine when using other than AC Delcos or NGKs. Hence the question.

    Hope you find a solution soon.

  7. #7
    00shortbox
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    Re: 5.3 misfire

    Quote Originally Posted by vvolk
    check intake for leaks.mainly left bank front cylinders. very common problem.

    That's what I was thinking, there is a TSB for this condition. The intake gaskets will cause air to leak into the cylinders and cause a lean misfire when the engine is cold. Once the engine warms up, the gaskets expand and seal properly, correcting the misfire.
    2000 Silverado RCSB
    4.3L V6, 5-speed
    16x8" Ion Alloy Wheels, P255/70/R16 tires
    Clear corner signals, K&N air filter, throttle body spacer. Magnaflow Catback Exhaust

    Certified Automotive Technician at a 5 line GM Dealer

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    Re: 5.3 misfire

    so what is the solution? does anyone have a link to the TSB? it was fine this morning it was 34 degrees when i started it, and its done it before at that temp. ill just see if the problem continues

  9. #9
    00shortbox
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    Re: 5.3 misfire

    The solution is to install the updated intake gaskets.

    99 through 05 GEN III truck engines may experience any of the following:

    1. A cold rough idle that diminishes as the engine warms up.
    2. Possible DTCS P0171, P0174, or P0300.
    3. Random misfires at idle.

    Recommendation/Instructions:

    The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

    1. If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
    2. The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.


    I obviously can't guarantee you that's the problem without looking at the truck, but I've fixed quite a few like this with the same complaint as yours.
    2000 Silverado RCSB
    4.3L V6, 5-speed
    16x8" Ion Alloy Wheels, P255/70/R16 tires
    Clear corner signals, K&N air filter, throttle body spacer. Magnaflow Catback Exhaust

    Certified Automotive Technician at a 5 line GM Dealer

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    Re: 5.3 misfire

    its gonna be real cold here tonight so i should know for sure in the morning if the plugs and wires fixed it.

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    Re: 5.3 misfire

    did it again this morning. guess ill take to my mechanic friend that works at the stealership to find out for sure whats causing it

  12. #12
    Black Beauty 02'Z71ONDUBZ''s Avatar
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    Re: 5.3 misfire

    Mine has recently started doing the same as described... My plugs are fairly new AC's. It sounds like it has a real lope for probably 2 or 3 minutes on really cold mornings. I have also noticed that the coolant has been becoming low... this has happened twice now. Could the gasket be causing coolant to leak?
    2002 Chevy Z71
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    Re: 5.3 misfire

    Quote Originally Posted by 02'Z71ONDUBZ'
    Mine has recently started doing the same as described... My plugs are fairly new AC's. It sounds like it has a real lope for probably 2 or 3 minutes on really cold mornings. I have also noticed that the coolant has been becoming low... this has happened twice now. Could the gasket be causing coolant to leak?
    Yes, I was getting ready to mention that to the original poster. Check coolant levels - head gaskets may be failing allowing for some coolent seepage after sitting. Condition will clear up shortly after startup once coolent is burned off. If SES light is up scan it to find which cyclinder is the culprit.

  14. #14
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    Re: 5.3 misfire

    diagnosis is intake manifold gasket leaking and had a couple injectors hanging up.

  15. #15
    Registered User ///M5's Avatar
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    Re: 5.3 misfire

    I have the same misfire and leak, but being it is 20 below zero I don't feel like pulling the intake right now. Is there any redneck engineering trick that would work temporarily? IE make a gasket or something?

    My truck is an '02 Silvy with the 5.3
    *I realize this thread is a year old, but considering it is exactly the problem I am running into I thought better to add to it.
    1991 BMW M5 -- Eclipse 8454, Eclipse PA5532, Seas W18E IB, Alpine-Scan D2904/6000, SoundSplinter Rli8 .65 tuned to 30hz
    2002 Chevy Silverado -- 880prs, Seas CA18RNX, LPG 25nfa, Mach 5 IXL-12, JL 1000/1 & 450/4

  16. #16
    Not Really Bob
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    Re: 5.3 misfire

    Only option is to replace the gaskets or wait for warm weather.
    99 Silverado ECSB 4X4, LQ4, Patriot Stg. 2 243's w/ 59cc chambers, TR224-112, Pacesetter LT's, Nelson tune, FLT Lvl 5.5, PI 3400, UD pulley, 160* t-stat, E-fans, 6'' Fabtech lift, 3'' body lift, 37'' XTerrains, 4.56's, 4'' shackle flip 13.3 @ 99mph on 37's or 13.0 @ 101mph on 31's

 

 

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