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  1. #1

    Default 98 silverado misfire

    5.7 vortech with new distributer, wires, plugs, intake gaskets, knock sensor, fuel pump, fuel filter, good fuel pressure, new heads. Say you take off from a stop light and are just easing into the throttle you get to 40 mph and the truck shifts into OD the truck develops a shudder or misfire(but there are no misfire codes, im assuming because it doesnt to it real bad, but i know its there and thats enough for me) if you just pick up the throttle a little it will go away or lay your foot on the brake and get it to shift back down a gear it will go away. I dont really know where else to look, ive checked for vaccum leaks also with no luck. Its had an egr code for as long as ive had the truck, and there has been atleast 4 of them put on the truck trying to clear that code, so it has been unplugged for years and never caused me any problems. any help would be greatly appreciated!!
    Last edited by rison15; 03-09-2011 at 05:09 PM.

  2. #2
    Jr. Engineer
    Join Date
    Aug 2010
    eas' bum fuk, maine


    are there any new codes? check the codes and let us know what they are.
    "i dont think you got the picture. i got a beautiful picture. this baby happens to have an extra turn of speed, which is the only thing i care about. you dont understnad what happens do you? they make cars. they make 'em exactly the same way. one or two of 'em turn out to be something special. nobody knows why. i know why. i may be kiddin' myself, but i think i can make somethin' out of that sad little bucket of bolts." ~ Tennessee Steinmetz

  3. #3


    I will take it tomorrow and let you know, thank you!

  4. #4


    Welcome to the club. I would try cleaning the MAF with some CRC MAF cleaner, its in a silver can. CRC is the only one that I've seen that makes the MAF cleaner. Its about $4.00-$5.00 a can so its a cheap try. Just follow the diections on the can. Also have you checked for new codes.

  5. #5


    I will try cleaning that, Im taking it tomorrow to check for new codes, I will let you know. Thank you!!

  6. #6


    ok, I took the truck to get it timed and the codes reread. The timing was off 8 degrees (which i knew would be off some cuz i just guessed when i put it in) it shows no misfire codes, all it shows is egr code and when the he clicked on it is said "low voltage"... shortly after i bought the truck it threw that same egr code and i put two new egr valves on it (thinking the first one was faulty) and then i was told that if i didnt mind the light being on that i could just unplug it and it would run fine. so thats what i did and it ran fine all those years and now this? My mechanic told me that it could be my tranny too?? It will only do it when its at operating temperature and at 40 mph when it shifts into overdrive and you start to lug the motor just a bit. he told me if i wanted to fix the egr i needed to ohm each of the egr wires to make sure that one wasnt broken, and if they were good that it was prolly the computer?? dont know what to do, spend a couple hundred on a computer and hope that works or?? Im at a loss. thaks for any help..

  7. #7


    I bought my ECM on e-bay and had the company i bought it from delete the egr and O2 sensors...cost $ 120 bucks !! WORKS PERFECT !

    1996 Suburban K3500 SLT DUALLY
    1988 Camaro RS 383 stroker LT1
    1992 32' Aero-tek Race Boat, 600 CI BBC

  8. #8


    DAREDEVIL, so you just leave the egr and o2 sensers on the engine and the computer acts like there not there?

  9. #9


    NO, you leave them there but you have to unplug them or the computer will see a But if they are deleted in the ECM the unpluging has no meaning to the ECM so your good to go and it works !

    Here is the link where i bought it.

    then you just contact him and tell him what you want, on mine i had him delete O2 and EGR, upgrade for 19.5's so tranny shifts correct and some other power mods!

  10. #10


    I would highly discourage against removing the O2 sensors. These are what give you the fine tuning of your fuel mixture, without them it runs on a baseline table and your computer no longer "learns" how the engine likes to be fueled. Unless you're a tuner, you want O2 sensors and closed loop.

    EGR delete will cost you a little bit in mileage, but can easily do without it.
    1986 Chevy G20 Tow Rig - 5.7 TBI conversion
    1978 Mustang II King Cobra Road Racer - Holley 650, MSD 6AL, 5 speed, 10 point Roll Cage, 9" posi, fuel cell, custom interior.

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