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2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

This is a discussion on 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start within the Technical / Maintenance forums, part of the General Discussion category; So a couple of months ago my truck decided that it would not start, though you could hear the pump ...

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    2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start


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    So a couple of months ago my truck decided that it would not start, though you could hear the pump priming. I really thought the guys at work were playing a prank on me in the parking lot,so after cranking, it would fire most times but not start. Did this prly 20 times. I let is sit for couple hours came back and it started right off. So I started it several times to make sure it was gonna start for me. About a month later, same thing. Wouldnt start one night. Tried again in the morning and it has started fine for a week now. I have replaced plugs, wires, rotor and cap but NOT the dist. yet. Took it to mechanic and he tested the psi, said it was like 55 just with the key in the aux position, so he said my pump was good. What do I do? Truck has 265XXX miles on it! I was thinking fuel pump relay, egr valve, spider system upgrade but $$$ at this point! The truck also seems to have a missfire at idle, you cant see it on the tach, but you can feel the truck shutter, and also I might add that I dont think this truck has very much power and the motor is supposed to have around 100k on it, but 265000 on the truck itself. Please help. I suppose I should have it hooked up to a code reader first even though no dash lights are giving any indication of problems? I want my truck to run good, be dependable, and have more power! thanks.

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    so I just took the truck down to the parts store and had it hooked up to the computer, and they said without the check engine light on that it wouldnt read anything, so we tried it anyway and there were no stored codes. So I bought a can of seafoam and dumped in the tank. I have a feeling have a dirty/malfunctioning spider system or a worn distributor gear, but shouldn't something like that cause a check engine light????

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    Registered User shamrock246's Avatar
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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    It might not be bad enouph to set the check engine light off but the new style spider makes a world of difference,the fuel pressure should be 62-66psi,the poppet failed overnight on my spider no cyl #5,the seafoam might help

    Sean

    97 4x4 burb

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    I was talking to the guys at the parts store and they had never heard of an upgraded spyder system for these engines. They said it must all be aftermarket stuff because they had never heard of it. So are these guys just ignorant, or are they correct in that all of the newer spyder system upgrade kits are aftermarket, not that it really matters. So which upgraded system is the best bang for my buck? how much should I expect to spend???? Will this give my truck more power, and better fuel milage? Currently I get about 10 around town and the day I bought the truck I got 15.6 going down the interstate which I thought was pretty good for a 3/4 ton truck with 4:10 gears. And that was actual mileage, not a lie from a vehicle computer!!

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    definatly do a gm pump! even if its just for peace of mind, and mass air flow can intermitantly screw up, and make sure u have gm ignition parts not cheapo napa crap. thats nothing but trouble.

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Quote Originally Posted by fasthorse View Post
    definatly do a gm pump! even if its just for peace of mind, and mass air flow can intermitantly screw up, and make sure u have gm ignition parts not cheapo napa crap. thats nothing but trouble.
    So change the pump anyway? I have heard the AC delco's are good, is that right? Also, are you saying to check the MAF sensor? And as far as the ignition parts go, I have brand new wires and AC delco rapidfire platinum plugs, and borg warner rotor and cap, I suppose that stuff is all crap.
    One more thing I might mention is that my gas gauge only works about half the time, could that indicate a bad ground somewhere like at the tank with the posssibility of a bad ground at the pump as well?
    I was also considering a salvage distributor, it only has about 15000 miles on it and the motor threw a rod, so would there be any harm in installing a used distributor on my truck. I am trying not to spend too much on this high mileage truck, but I want it to run good to, so we gotta strike a balance somewhere.
    Thanks

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Upgraded spider

    http://www.amazon.com/Delphi-FJ10566...1997&carId=001

    pump assy

    http://www.amazon.com/Delphi-FG0085-...1&s=automotive


    I would only use AC/DELCO fuel pump and ingnition parts i would do the pump and filter also with that milage i did on mine

    Sean

    97 4x4 burb

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Upgraded spider

    http://www.amazon.com/Delphi-FJ10566...1997&carId=001

    pump assy

    http://www.amazon.com/Delphi-FG0085-...1&s=automotive


    I would only use AC/DELCO fuel pump and ingnition parts i would do the pump and filter also with that milage i did on mine

    Sean

    97 4x4 burb

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Quote Originally Posted by jwilkey84 View Post
    So change the pump anyway? I have heard the AC delco's are good, is that right? Also, are you saying to check the MAF sensor? And as far as the ignition parts go, I have brand new wires and AC delco rapidfire platinum plugs, and borg warner rotor and cap, I suppose that stuff is all crap.
    One more thing I might mention is that my gas gauge only works about half the time, could that indicate a bad ground somewhere like at the tank with the posssibility of a bad ground at the pump as well?
    I was also considering a salvage distributor, it only has about 15000 miles on it and the motor threw a rod, so would there be any harm in installing a used distributor on my truck. I am trying not to spend too much on this high mileage truck, but I want it to run good to, so we gotta strike a balance somewhere.
    Thanks
    seen alot of misfires from napa plug wires arching on nearby components, yes clean your mass airflow sensor with throttle body cleaner or electrical cleaner they get dirty and act stupid sometimes. yes use ac components on everything u can. And yes gauge problems usually related to in tank issues GM pumps are rated to 60k miles but my last one lasted 110k. used distributor should be fine if u see no damage.

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    due to your low pressure and sporadic fuel gauge i would guess its the sending unit. gm ones have issues with the connector being sporadic anyway the new delphi ones ( the ones he linked) come with a new harness that has to be soldered in, no dont use butt splices that come with it. when i replaced mine though the pressure was right made the crappy poppet injectors run really rich so i ended up replacing the new mpfi, filter, and pump within a few months. runs better than even now though.

    as far as the distributor how do you know its got less miles, alot of people throw the old parts in the new or rebuilt engine. and you have to have your timing set with a scanner (cam retard to zero) after you pull your distributer
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    forgot to add the pressure regulator is included and mounted to the new mpfi kit so if thats your issue its replaced
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

    87 Firebird, 07 Monte Carlo lt, 98 Bonneville SSE, 04 F550 CC 4wd service body

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    alright, so my truck didnt want to start for me this afternoon again! It started fine this morning, but at 4pm just crank, crank, crank, fire, try to start, start for a second........die! tried several times like 15, nothing. Walk away for 20 minutes come back and it started up and I have drove it all night. I went to the parts store and got a new fuel pump relay, and cleaned the MAF sensor, still notice a shudder in the motor at idle. So what should I try next, distributor?? or fuel pump? Everytime the truck does this I can still hear the fuel pump buildig pressure when I turn the key to the on position, can the pump be weak and still work most of the time? I have also heard some bad things about the distributors on these truck, esp the ones with the plastic base, which mine has. So I might get the pressure checked again, I need between 62-65psi right? also, what kind of scanner does it take to reset the truck after I put in a new distributor, the little shop I have been talking to is a pretty small town small business, I wonder if they would even have the right tool to reset the timing afterwards, any thoughts?

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    get pump first thing they will still run just half ass, and at work we use the tech II scanner for setting the timing. i should know the specs cuz i have the same truck but i dont rite now haha.

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    you dont have to have a tech 2. just the more expensive scanners. i found a local guy that knew what i was talking about its hit or miss though and almost guarantee the one answering the phone wont
    99 GMC Yukon SLE 4dr
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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    With that kind of milage i would start with the pump assy and fuel filter do the harness upgrade and work your way foward and stick with AC/DELCO ignition parts

    The autoxray 6000 reads cam retard from what i hear mine is on order
    Sean

    97 4x4 burb

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Quote Originally Posted by shamrock246 View Post
    With that kind of milage i would start with the pump assy and fuel filter do the harness upgrade and work your way foward and stick with AC/DELCO ignition parts

    The autoxray 6000 reads cam retard from what i hear mine is on order
    ok, I'll start with the pump assy, but keep in mind that at least most of the time the truck wont start, I can still hear the pump building pressure when I turn the key.

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    Quote Originally Posted by shamrock246 View Post
    The autoxray 6000 reads cam retard from what i hear mine is on order
    I have the 6000 and it does in fact read CAM RETARD.

    Quote Originally Posted by jwilkey84 View Post
    I can still hear the pump building pressure when I turn the key.
    Just because you can hear the pump doesn't mean it's building pressure.
    Mark
    97 K2500, 5.7, 4L80E, 4.10 Posi

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    So after new plugs, wires, rotor, cap, distributor, fuel pump, fuel pump relay,..........I finally had the truck hooked up to the computer and turns out it has both 02 sensors bad, a #4 cylinder misfire at idle, almost constantly, and a code for a security thing that is actually the cause of the truck not wanting to start sometimes. So I guess I'll upgrade the spyder system to get rid of the misfire, and get new 02 sensors to hopefully up the MPG's a little, But how do I go about fixing or bypassing the security issue, has anyone ever had this problem and is it common?

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    Re: 2000 gmc classic, k2500 5.7 vortec misfire at idle, sometimes will not start

    i think technically the only way to completely bypass it is to tune it out of the pcm
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

    87 Firebird, 07 Monte Carlo lt, 98 Bonneville SSE, 04 F550 CC 4wd service body

 

 

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