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2000 Tahoe Vortec 5.7L, rough idle

Discussion in 'GM Powertrain' started by J3., Jun 16, 2009.

  1. J3.

    J3. New Member

    Hey guys, I'm new here.

    I recently bought a 2000 Tahoe Limited with the 5.7L Vortec and about 150k miles on it. It had been running fine, but the SES light was been on so I went to have the codes checked. I don't remember the numbers but there were two codes being thrown: Random misfire and Insufficient coolant temp.

    I checked the plugs and they definately needed replacing, so I put in new plugs and plug wires and replaced the fuel filter and PCV valve. Ever since I changed the plugs and wires though it's been running badly. It starts up fine and runs good for about a minute, but then the idle starts loping every couple seconds and everything shakes. I put a timing light on it and during the lope the timing mark on the balancer is dropping back to the right(driver's side) a few degrees, then it returns and the engine sounds fine, then it lopes again...

    I've double checked the plug gapping as well as the plug wires and they're all in the right place and clamped on correcty. I've searched around for info and I'm thinking maybe it's the ignition coil?

    Thanks for reading and any help would be greatly appreciated!!!
  2. redneckarmyMP

    redneckarmyMP Epic Member 5+ Years 500 Posts

    could be the coil..but im thinking the catalytic converters may be stopped up or o2 sensors may be bad
  3. crazi

    crazi New Member

    I have the same problem in my 98 Silverado 5.7L. I just got it back last weekend and it still has a rough idle. I have got the Distrubutor changed and the thing called a "Spider" Something to do with my fuel injection I think. But I also need to know what this problem is. I hate driving it when it idles rough.
  4. grimreapersshadow

    grimreapersshadow Rockstar 100 Posts

    i would check out your thermostat temp sensor up at the top of the top of the motor by the thermostat housing a wrong signal can also create that symptom
  5. daddytech

    daddytech Epic Member 5+ Years 500 Posts

    first thing i would ask is what type of plugs did you put in it. some of them don't do so well in the trucks because they are too hot of a plug, they'll work but some times they can cause problems.

    I run E3 plugs in all of mine, they are expensive but deffinately worth it. Might also try running some sea foam through the motor also just to eliminate that your motor might be gummed and varnished up and that might be causing part of the problem too.

    Last if you have a true 2000 limited you really need to hang on to that thing. they didn't make many of those and that is actually the SS of the tahoe's that GM didn't actually manufacture until after 2000 there's a whole article on it on wikipedia.org was kind of an interesting read.

    be sure to post your resolution on here so that everyone can benefit from your experience.
  6. J3.

    J3. New Member

    Thanks for all the replys everybody!

    I put in NGK G-Power Platinums. I always use NGK plugs and never have had any trouble with em before. I've read that platinum plugs do run hotter, but I don't think they'd be hotter than an e3 plug though...? I've heard good stuff about SeaFoam; have to try that. Can you buy it at autozone or where?

    daddytech, what's the story with your 99 Tahoe and the 9c1 badging? I've been a follower and fan of the 94-96 Impala SS and 91-96 Caprice (really all the B bodys) for a while, so I know quite a bit about the 9c1 Caprices. Never heard of a 9c1 Tahoe though.

    Yes, mine is a true Limited SS. Full police package suspension, 120mph speedo, ground effects, etc. That's a lot of the reason why I bought it. :) It's a 1 owner and I bought it from a friend of mine who owns a used car dealership. The wiki article says they only built 8,905 of em. I know it's only the second one I've ever seen.

    I'll definitely post up and let ya all know when I get it figured out.
    Last edited: Jun 18, 2009
  7. daddytech

    daddytech Epic Member 5+ Years 500 Posts

    NGK's are good plugs too not too hot and they last a good while. never used the platinums but back when i had my Mazda 929 that's all i could run in it and it work right. still have a set out in my shop i need to take back to Advance come to think of it . :eek:)

    Yeah you can get sea foam from Advance and I have seen it for a time even at Walmart. That stuff is like gold. it'll totally clean your motor. just ran some through a friend of mine's motor through the intake and in the oil also just before he pulled it and tore it down for maintinance and that sucker was clean inside. it's a truck he races with on the weekends locally. he was totally amazed that there wasn't any varnish at all inside his motor as long and hard as he runs it (talked him into the mobil 1 thing too and he's lasting a lot longer between total rebuilds now)

    the 9C1 decals were on my truck when i got it . I am sure someone just put them on there because they thought they looked good, either that or they are hiding more unrepariable scratches like the purple decals that were on it also when i got it.

    Mine also has the police package on it with the 120 mph speedo, thicker anti sway bar beefed up suspension, 240 amp alternator towing package and all the trimmings. Mine actually came factory with tahoe SS emblems on it but there are so many of the police package items on it i think someone goofed. should have been listed as the Z85 police package i think or what ever the Z label is supposed to be for the police package of this year model. I am taking that 9C1 off soon. the only reason i left it on there was because of all the decals it was the better looking than any of the emblems that were stuck to it, plus that whole red & black thing actually looked pretty good.

    Guess I am a little clueless about all that. I also thought the actual police package had a 130 mph speedometer for some reason too but i went back and looked at several different sites and it is 120 so i guess mine is a full on police model too then. I would have liked to have had a 2000 limited but they are kinda scarce, and rarely seen for sale any more as you pointed out. Besides when i bought mine i only had $5,000 to spend on one and the few limited's i saw for sale at the time were going for $8,000 - $10,000 I just couldn't afford to do that though specially not with 5 kids.

    My pride and joy is my 89 silverado sport though mainly because there were so few of them made to begin with that year and fewer of them still around now. mine needs a paint job now though and finding the replacement logos is proving to be an impossible task.

    Savor that truck man it's not just a really nice truck but also a rare collector. nice purchase I'm jealous , :lol:
    Last edited: Jun 19, 2009
  8. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    A coolant temp code would cause your system to remain in open loop. In open loop the engine will run rich as the computer is trying to keep your engine cool.
    Instead of throwing parts at your truck you should fix the codes. The codes are there to help you diagnose the problem and give you a starting point to work from.
  9. J3.

    J3. New Member

    Wow, that's pretty impressive. I'll definitely pick some up next time I'm at the parts store.



    Huh. Yeah to have all that on it but not be a Limited it almost sounds like a custom order or something. Maybe a COPO like the dealers did back in the 60s and 70s haha.




    Yeah I think I'm gonna just take it to the dealer and let them diagnose it for me. I don't want to be wasting money replacing stuff that's fine.
  10. k.daddy1

    k.daddy1 Rockstar 100 Posts

    I had the same problem with my 01 silverado, the fuel pressure regulator fixed my problem.

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