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Chevrolet Tahoe Misfire



  • $250 More
    Ok, just put in 4 brand new O2 Sensors, 3 of them looked like caked on chalk. When started the first time, engine light blinked, misfire P306 and P507 Throttle position sensor. Cleared the code drove about 60 miles hasn't returned yet. I also haven't started it cold yet. I'm also running can after can of seafoam, I still think misfire in 6 has faulty fuel delivery, clogged injector? What do you think next? Grrrrrr!
  • rem222rem222 Posts: 4
    1998 Tahoe LT multiple misfire codes P0300 - P306. I experienced ALL the symptoms mentioned this subject including a dealer telling me my engine is shot. OK - I need a second opinion.
    Took it to my mech Mike Tieg, Tieg Automotive, Greenwood Mo. He had it three days and called me stating he thinks he figured it out, 99% confident, but it isn't cheap. He replaced the fuel distribution spider to the throttle body fuel injection under the intake. He was spot on!
    Put another 100K on it and sold it earlier this month w/ 224K on it.
    Loved my Tahoe for 10 years, now I love my Denali 6.2 L.
  • rem222rem222 Posts: 4
    Johnny - Read my post - last one this string
  • hquickhquick Posts: 5
    I know this may be a bit late...but anyway...
    How do you guys clean your own injectors?
    As far as I'm aware the CSFI 'spider' poppet injectors can't be cleaned without removal. This means the upper half of the intake manifold needs to be removed.
    If you're going to that'll do well to replace the whole injector setup with one of the 'mini' injector units. These are 'proper' injectors....not ball bearing valves at the end of hoses (poppets).
    The other common issue with these trucks/SUV's is the distributor gear wears unevenly and gets 'knife-edged' on one side.
  • rem222rem222 Posts: 4
    Good call, re; the distributor gear, many miles will wear the gear as you describe. That info coupled with the spider info should eliminate much of the guess work about multiple misfires in the many past posts calling for help. When a misfire is localized to a specific cylinder and not random one of the two mentioned above is more than likely the culprit. As far as cleaning the spider - Agreed, you've come this far, replace it (Parts, and Labor it isn't cheap though ). If you want a cheap try - go to your local Yamaha dealer and get a bottle of Yamaha Ring Free and shock treat according to instructions on the bottle. Forget the fuel injector cleaner stuff - Ring Free is designed to destroy carbon. OMC also has a product, just not as concentrated so you use more but they both are effective carbon control. To my knowledge they do not harm O2 sensors.
  • Did you change your O2 sensors on the side with the misfires?
  • momsbusmomsbus Posts: 3
    bought a new 5.7 crate motor for our 97, installed it with new spider injectors, new distributor cap & rotor and fired it up to a misfire problem we can't seem to fix. Cyl.#3 is the one causing the problems, changed plug already and it's still doing it. Going to change O2 sensor next, but any suggestions from anyone would be helpful.
  • I don't know how many people I've already told this to but it is your O2 sensors. Trust me, trust me, trust me. Simply unplug your left upstream sensor and fire it up, if the misfire is gone then that's the one. If not, do the same thing with the right (upstream) sensor and fire it up. How much did the engine cost? :D
  • momsbusmomsbus Posts: 3
    I will go with your suggestion,but I don't understand how a bad O2 will cause only one cylinder to create a misfire? I have changed the plug (has been changed 3 times)-plug wire checked and a injector balance check done on all 8 cylinders
    which all check out working correctly. I have an good scanner and it shows the upstream 02's working (Correctly I'm not sure of the parameters) I have even removed the upper plenuim to check that the new injectors were seated properly. The motor cost a little over 2k plus a new distributor and injector spyder and all filters and fluids and knock sensor and temp sensors and gaskets.
    Thanks for the input and we will run with it, Any other thoughts let us know
  • momsbusmomsbus Posts: 3
    Changed all 4 O2 sensors and I still have #3 and now #5 giving us a misfire......any other suggestions? Anyone? Gonna take the plenuim off again to check these two injectors....but any suggestions are welcome.
  • I have read your reply`s but try this one on for size and if anyone can help i would reall appreciate it.
    I have a 97 chevy 1500 withh a 5.7 vortec. I started developing a misfire every once and a while. maybe every 3 0r 4 weeks to 6 weeks apart, Then started getting it everytime i accelerated a little more than usual or going up an incline for a decent amount of time. First of all changed the fuel filter to see if it was clogged, no help. Second the plugs and wires which have been changed 3 times currently with ac delco double platnum irridum. no help still have a missfire. Changed my distributor cap and rotor cap 2 times to make sure no cracks, still misfire after going down the road and accel to higher speed. Pulled off the upper intake expecting to find poppers in there but no, it had spider already installed, but guess what, I pulled it and put a new one in, making sure all injectors are in correct cylinders. Checked this 3 times before putting upper cover back on.Still misfire continues. Then the fuel pump goes out, how convienient. Replaced the entire assembly. still missfire continues. I replaced the ignition coil, no help. finally discusted after having the caty convertors checked and testing the 02 sensors which all checked out fine, I had a new distributor put in yesterday. took of from the shop and got 3 miles away and missfire on #5 has once again returned. NO vacume leaks and not bad compression. Idles great and starts perfect runs great until you accel too much or going up a hill or sometimes out of nowhere it starts in again. I have gone 2 to 3 days without it doing it off and on , but it comes back. Crankshaft sensor , camshaft sensor timing on dist, plugs all on the mark. what do you think about this one????? Contack me personally if you like at
  • whats the drumroll for? iIt didnt fix the problem! Appreciate your info anyway.
  • I also has a 99 5.7 GMC Yukon 164,000 miles, owned 2.5 yrs, have replaces Dist cap 4 times, each time cap had heavy corrosion on contacts, finally replaces complete Dist, ran well for 6 months, now have general misfire code, Have read thru the various posts and have not seen any comments on inside of dist cap condition, would o2 sensor cause cap corrosion, I'm going to start towing a trailer soon and need to get to the bottom of this, sounds like this is a GM common problem, I was told my coil might be to hot, (?) HELP
  • dtheodore76dtheodore76 Posts: 2
    Thank you guys for all the info. I have a 98 Suburban 5.7 vortex I've been going through the same issues. I got this truck after my father-in-law passed away. Before he died he was having issues when he drove for an extended period, it would lose power and shut off. After sitting up it would start up and he would be on his way. Learned it was symptoms of a clogged cat. So, I changed those, then it threw a code for the camshaft positioning sensor. Changed that and now threw a code for a crankshaft positioning sensor. Oh, by the way, it also had code for misfire on #4. Got my fingers crossed hopefully it works.
  • dtheodore76dtheodore76 Posts: 2
    edited April 6
    Oh I forgot, after changing the cats, I let the engine idle then accelerated to 2000 rpms After about 4 mins the manifold was glowing red on the driver side. That's when I got the code for the camshaft sensor. After it was changed, manifold no longer glowing red. Don't want to keep throwing money on it, just want to get it going.
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