Results 1 to 12 of 12

p0303

This is a discussion on p0303 within the General Help forums, part of the LSx Technical Help Section category; 98 Z28 5.7 A4 180,000 miles Started off with a P0303. I cleared the code changed the plugs and the ...

  1. #1
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    p0303

    98 Z28 5.7 A4 180,000 miles

    Started off with a P0303. I cleared the code changed the plugs and the wires still had a miss but no code. I changed the fuel filter and ran the 3M fuel injection cleaning system through and after that it ran better. Left the driveway wemt down the street - started missing. Checked codes and got P0300 and P0303. I ran Seafoam through seemed to be great. Took it for a test drive and after getting on a few times it started to miss again but no code.

    What should I check next?

  2. #2
    Super Moderator
    pajeff02's Avatar
    Join Date
    Feb 2009
    Location
    Mansfield, PA
    Posts
    21,567

    Black & Blue
    '02 WS.6 / '07 Suburban

    Are the wires properly seated on the coils -- 2 clicks? Did you test the coils? Any chance you burned a wire on the exhaust? Cracked a plug insulator?

    Might try to run the engine at night with the hood up and see if you have any spark jumping around.

  3. #3
    Junior Member hippiespace's Avatar
    Join Date
    Apr 2008
    Location
    Ashburn Virginia
    Age
    37
    Posts
    65

    Navy Blue
    2013 ZL1

    02 and cats

  4. #4
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    No mods on this car. Wires are not even close to the exhaust and seated good and tight. Insulators are good. When I quit it was Dark could not see any noticeable arcs.

    Didn't run my hand through there though to check.

  5. #5
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    After I ran the 3M injector cleaner it was showing an 02 code but I figured that that might be because of everything going through. Ever since I drove it around it does not show the 02 code anymore.

  6. #6
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,996

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    try swapping the #3 fuel injector around with a another one and see if the miss follows the injector. Same test can be done with the coil, plug or plug wire.

  7. #7
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    I will try that tomorrow and see wht happens.

  8. #8
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    Ok I switched the #1 & #3 coil drove around for a while with a miss. It took a while to trip a code. I am using AutoTap Diagnositic Scanner. It came up with

    P0141 H02S Heater circuit Bank 1 Bank 1 Sensor 2
    P0157 H02S Circuit Low Voltage Bank 2 Sensor 2
    P0300 Engine Misfire
    P0303

  9. #9
    Senior Member Too Fast's Avatar
    Join Date
    Nov 2006
    Location
    Indianapolis
    Age
    54
    Posts
    5,170

    Black
    2000 WS6 6spd Hooker LT

    More things to try....like Cutlass said, move an injector to Cyl number 3. As far as the P0300, that is a multiple cyl misfire.

    Have you cleaned your MAF. Dirty may cause lean issues, which may result in misfire P0300.


    You may have a bent pushrod #3. Self explanatory, but sometimes this will have a ticking noise associated with it.


    Does it miss only at idle/low speed? If so, rare but could be a barely stuck open EGR. Usually this only causes the P0300, not a specific cylinder.

    O2 sensor code P0141 looks like bad B1S2 O2 sensor, and probably same for B2S2. Usually a lean condition won't trip rear O2 codes. Maybe front O2 codes, and rear 02 codes usually don't have anything to do with driveability problems like a misfire. There are some exceptions, of course, like if the rear O2s have shifted so much that the PCM is commanding too much fuel due to the lean reporting (low voltage).

  10. #10
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    Yes I cleaned the MAF. I will swap the injectors tomorrow and see what happens. Yesterfay after using the Seafoam It ran pretty good for a little while and progressively got worse. Even though it has a noticeable miss it takes a while before the SES comes on. It seems to run pretty good under a load.

  11. #11
    Member FMBL's Avatar
    Join Date
    Mar 2010
    Location
    NRH, TX
    Posts
    161

    White
    1998 Z28

    Swapped plug wires and disconnected battery and it seems to be running fine. Good enogh that it passed inspection. ??????

  12. #12
    Senior Member Too Fast's Avatar
    Join Date
    Nov 2006
    Location
    Indianapolis
    Age
    54
    Posts
    5,170

    Black
    2000 WS6 6spd Hooker LT

    Maybe it was a plug wire not snapped on completely, and now it is.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •