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HELP Check Engine Light Flashing

Discussion in 'Chevy Trucks' started by mkwl, Sep 4, 2009.

  1. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    :realmad:On my way up to school, driving at around 70+/-MPH for about 2.5 hrs, my check engine light started flashing about every 15-20 minutes (would flash for 3-18 flashes each time) then go off. GM manual says this is a misfire detected in the engine- any thoughts? Is it going to be a problem to drive the truck as is until I can get it looked at (middle of next week)? The truck had flashed like this in the past, but never so much all in one trip. It seems to only do it when I'm driving on the highway.

    I'm thinking it may be the need for new wires/plugs. I'm going to have a GMC dealer install them- any idea what I'm looking at cost wise?

    Not sure if it matters, but I recently put in a K&N drop in air filter.

  2. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,912

    The filter shouldn't have done anything bad unless you knocked you mass air flow sensor out in the process. Check your spark related parts like plugs, wires, modules, and sensors you can readily reach.

    Do a quick visual check through the engine compartment first to make sure everything is hooked up. You might have knocked something loose.
  3. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    Is there any good way to check the wire/plug condition?

    How hard is it to replace the plugs and wires? Proper procedure?

    How much for the GM parts?
  4. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,525

    ck the code but. But sometimes the oil from the k&n gets on the maf and causes issues. But get it scanned could be a thousand things.Then go from there. Otherwise a never ending guessing game
  5. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    How many miles on this engine?

    It time for tune up.
  6. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    About 72,000 miles on the truck.

    Is running the truck with the light occasionally flashing (usually only on the highway) going to damage anything until I can get it looked at?
  7. mcginner

    mcginner Junior Member
    Messages: 20

    When the engine light is flashing it means you are doing harm to the catalictic convertors which are very expense for those truck and have a chance of plugging up and cause your truck to run like a bag of crap.
    Get the truck check by a pro to see why the light is on. You most likily do need new plug & wire set, a fuel filter would be a good idea too.
    Also the oil from the K&N filter can cause problems with the MAF sensor. Clean the sensor with brake cleaner.
  8. stillen

    stillen Senior Member
    Messages: 247

    mine would flash, it was a p0304 code, cylinder four was misfiring..... The flashing means unburnt fuel was headed down towards the cat,,,,, thats bad...... butmy truck had 270k on it. it was a 2001, 5.3.... ran like a champ, i traded it for my dodge...
  9. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Mine did that too, flashed occasionally and go off. It turned out to be a bad O2 sensor. But keep an eye on the MAF, those oiled air filters suck. Get some good MAF cleaner by CRC and clean it up good. Possibly invest in a nice dry flow filter in place of the K&N. Much better for your engine. A tune up is easy to do, shouldnt take more than 20 minutes in your drive with very, very basic hand tools ( ratchet, plug gap gauge, extension and 5/8 deep well socket.) The plugs are kind of pricey but it will run much better after that. Dont pay a bunch of money to a dealer to tune that thing up. Should cost under $100 to do it yourself. And it is not like you could cross any wires, lol. But get the code scanned instead of the guessing game.
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    NO! NO! NO!

    Only use Mass Airflow Cleaner on your MAF. You can get it at Autozone, CRC produces it. When you clean the MAF, use only the spray, and do not touch the wires with anything. No compressed air, Q-tips, the spray nozzle, nothing.

    If you have an oiled K&N filter upstream of your MAF, get rid of it. If it hasn't already, it will cost you a new MAF. They shouldn't even sell those things. Get a nice paper filter. WIX or NAPA Gold. All those K&N do is let more dirt in your engine, and lighten your wallet. The stock paper filter is more than capable of flowing enough air at WOT.

    Sounds like a full tuneup is in order. Pull the Throttle body and clean it. Put some SeaFoam through the intake. New AC Declo plugs. For wires, ACD or Napa premium.

    Don't forget your fuel filter and PCV Valve. And at your mileage O2 sensors may be in order. They can slowly go bad, without throwing a code.
  11. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,525

    lol never seen iridium plugs go bad by 70k
    This thread will go on for ever til we get a code!
  12. nightandday

    nightandday Junior Member
    Messages: 12

    I believe if this is a 6.0 366ci. gas job you will find that a coilpack has gone bad. find out which cylinder is throwing the code. Also did you power wash the engine or degrease it recently? I did both to my 01 2500hd and burn out a coil pac. truck ran fine at first but in a matter of two driving hours it-would no longer idle correctly. A wet air filter (one containing spray oil is not the wisest choice in my opinion it has the ability to pick up to much fine particles if it is oiled by you upon your purchase. the k&n is pre oiled and in the consumer reports it falls near the worst filter, due to the fact that it impedes air flow rather than promote it . hope that helps
  13. Cosmic Charlie

    Cosmic Charlie Senior Member
    Messages: 237

    Bad coil pack according to my ASE mechanic, mine was failing at hiway speeds but ok around town. I woiuld reset the check engine light and drive ONLY around town for 2 weeks and it would pass inspection, but later on the hiway the flashing light would come on, and stay constant later - until I repeat the procedure for next years sticker, 3 years of stickers and counting !

    ps I usually don't drive this truck on the hiway ... just plowing and boat launching, I would have it fixed if you drive on the hiway regularly, I don't

    again I don't usually drive on the hiway and my coil pack is fine at under 40 MPH (+-)
  14. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    Okay- any idea how much a coil pack is (installed)? I'm going to try and get it scanned on Tuesday- will know better then what it will need.
  15. nightandday

    nightandday Junior Member
    Messages: 12

    I would guess it is going to be around $75 USD but You may need more than one
  16. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    Okay- not too bad- I assume the coil pack is easily accessible (the unit the wire connects to off the plug)?
  17. nightandday

    nightandday Junior Member
    Messages: 12

    That is correct. It is a realy easy fix to do yourself also if you find out which pac went bad they should be able to tell you that much and what the location of it is. I know the dealers in my town are $90 / Hr
  18. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    Okay, now, when I get it scanned- how will I know if it's the pack that's gone bad, versus the plug, versus the wire.....?
  19. Newdude

    Newdude Senior Member
    Messages: 889

    If you have 2 cylinders misfiring and they run on the same coil pack, I would think you'd have to check for spark. If there isnt any, that could tell you if power is leaving the coil for that cylinder or not. If the coil is fine, you ccan check the resistance in the plug wires.
  20. mkwl

    mkwl 2000 Club Member
    Messages: 2,362

    Okay- going to get it scanned (hopefully) after class today. the thing that puzzles me (and a mechanic friend of mine) is why it only seems to do it at highway speeds (60-72 MPH), and it's very sporatic- sometimes 30 flashes, sometimes just 3.

    Does this sound like a coil? It runs fine, if the light wasn't flashing, I wouldn't even know there was a problem.