1996 k1500 4x4 5.7 automatic misfire mystery

Discussion in 'Chevy C/K Truck Forum' started by Randy_H, Oct 7, 2012.

  1. Randy_H

    Randy_H New Member

    I have never posted for help on a forum before........but I am at the end of my rope.

    Multiple random misfires on random cylinders under load.

    I have installed new:
    Cam Position Sensor
    Crank Position Sensor
    Distributor cap and rotor
    Plug wires
    Spark Plugs
    Catalytic converters
    All O2 sensors
    Fuel pump and sending unit
    Fuel filter
    MAF sensor
    Air temp sensor

    I haven't had the truck long.....not even long enough to get inspection and tags. I drove it for 70 miles Friday afternoon without incident.....later that evening the misfiring started.

    No codes. Seems like it is losing current....the reason I say this is because without disconnecting the battery the clock on the radio resets randomly.

    PS: no miss at idle no matter what rpm.

    Any input would be greatly appreciated.

    Last edited: Oct 7, 2012
  2. MrShorty

    MrShorty Moderator

    I've had similar problems that I traced to a loose connection at the battery post. Grab a wrench and quickly check to make sure those connections are clean and tight.
  3. moogvo

    moogvo Moderator

    What kind of plugs and wires did you use?
  4. Randy_H

    Randy_H New Member

    I will try this in a few.....I didn't even think of that.

    - - - Updated - - -

    omni pro OE wires (don't know much about them took Oreilly's advice)
    acdelco iridium (every chevy I have had spark knocks without ACDelcos)
  5. Randy_H

    Randy_H New Member

    PS: cam retart at 0

    PS: cam retart at 0

    just thought I would add that info.
  6. moogvo

    moogvo Moderator

    I don't know anything about omni pro wires other than that I wouldn't use them. you need to use AC Delco wires. If you can't find them, you can use Borg Warner (BWD) wires. I have had good luck with those. Get a good set of wires and go from there. I can't begin to tell you how many times I replaced plug wires with something other than AC Delco or BWD and the problem didn't go away. The guys at Advanced O'Reilly Zone stores don't have a clue! You'd be better off buying the OPPOSITE of what they tell you most of the time!

    What do you mean by that? Did you adjust the timing? After 1996 you can't adjust timing without a scantool... Just so we are both on the same page... Input from the knock sensor (among other things) tells the ECM how much to advance or retard the timing. Yes, base timing is 0*, but you can't set the base timing with a timing light. you have to use a scan tool.
  7. Randy_H

    Randy_H New Member

    I will pick some up in a few and install them.

    I have a snapon ethos scan tool on it....from what I have read (I am no expert) when you change the distributor these are the steps:
    1. cylinder 1 TDC
    2. rotor to spark wire 1
    3. bring to operating temp
    4. bring engine to >1000 rpm
    5. read cam retard position and turn cap until within +/-2 degrees of 0

    - - - Updated - - -

    I pulled both battery terminal wires and wire brushed them.

    This in turn reset the PCM, I drove very easy until operating temperature then I did 5-6 crank and turn offs. I received a P0304 code.

    I changed the Camshaft Position Sensor reset PCM and still has code.

    The miss is not "as" bad as it was however it is still there.....does not show up on the live data scan tool now. And it seems like it does not have all of the power....well I know it doesn't it bogs down during a power brake instead of turning the tires over.
  8. Randy_H

    Randy_H New Member

    I just installed brand new BWD plug wires

    I let it idle 5 minutes, then cut it off and cranked it a few times then backed out of the garage and drove to the end of the driveway.....where it started missing and the clock flickered a couple of times and reset to 1:00...then the engine sputtered and cut off.

    It started right back up but now it idles horribly and I have a couple of codes.....
    P0118 Engine Coolant Temperature Sensor High Input (scan tool reports the engine temp at -40 F)
    P0304 Camsahft Position Sensor Problem
    P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage

    I am headed to pick up a temp sensor now.

    - - - Updated - - -

    Could it be the PCM?

    The PCM in this truck (1996 k1500) has no tags but I have researched out that it should have a PCM with service # 16244210
    I have a great running 1997 c3500 with 454 with PCM with service # 16229684

    Question is.....can I test with the PCM from the c3500 with 454?
    Last edited: Oct 8, 2012
  9. Randy_H

    Randy_H New Member

    Installed new BWD temp sensor....idled OK

    Test drive....misses horribly.

    P0304 code gone (even after several test drives)

    Initially it had these codes:
    P0118 Engine Coolant Temperature Sensor High Input (scan tool reports the engine temp at 180 F)
    P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage

    I traced the temp sensor wire and found the PO had either broke the wire or something so he had put in 2 butt connectors....I pulled the pin out of the connector and removed the butt connectors and connected the wire back to the OE connector.

    Still has the two codes:
    P0118 Engine Coolant Temperature Sensor High Input (scan tool reports the engine temp at 180 F)
    P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage

    I will add that before the temp sensor change the inside gauge showed about 150F and now it shows about 235F

    It is back to idling OK but misses during test drive whether it is hard or soft acceleration.

    Last edited: Oct 8, 2012
  10. moogvo

    moogvo Moderator

    This is a bit of a head scratcher... Let me think on this one before throwing more parts at it...
  11. PantheraUncia

    PantheraUncia New Member

    The only thing I did not see listed is have you checked the ground cables? (negative from the battery to engine ground and chasis ground) ? A bad ground can do allot of strange things.
  12. Randy_H

    Randy_H New Member

    I removed both and confirmed that they are not corroded and are tight. Sorry I didn't mention that before.
  13. Randy_H

    Randy_H New Member

    I took the dash apart to see if the radio just had a loose connection and if it was a separate issue. I can't confirm that yet...so far the radio hasn't reset to 1:00.

    Just for fun I cleared the codes and test drove......went about 1/2 mile and it started missing again check gauges light came on and the temp gauge was at 255 degree (just before red)....it almost choked off while I was turning around check engine light came on and it limped home. Hooked up the scan tool and temp reported was 180 degrees.

    I have a few calls out to see if any friends have a PCM.....I am afraid to use my c3500 with 454 as a test PCM without someone confirming it will work....I would rather blow $40 at a salvage yard for the known correct PCM.

    Tomorrow I am going to check the ohm's on the temp wire from PCM to sensor. I am also going to add a new ground wire just for my own peace of mind.
  14. Randy_H

    Randy_H New Member

    Try this on for weird.......

    I tested the temp sensor wire and could not find anything wring with it. So I decided to go change the new temp sensor in case new one was a lemon. Installed the new one (engine cold and not cranked all night and day) the in dash temp gauge needle went about 1/4 inch past the red 260 degree mark.....I tried to crank it and the check gauges light came on and it was very hard to start but it started and ran very poorly.

    I decided to put the old temp sensor back in just so I could move it out of the garage.
    temp gauge showed 100 degrees....it started right up and check engine light came on.
    I scanned the code and it was P0304.....I ran live data and cam retard was at -45 degrees.
    I decided to go ahead and turn the distibutor again and see if I could get it back near 0....I adjusted to 2 degrees.

    I let it idle for about 10 minutes then started and shut off about 5-6 times......the code went off and I drove it around the block 8 miles. No codes.....no misses.

    I am not happy...sure it runs but what was / is wrong with it. Hard to trust it.

    Sometimes I think I am talking to myself......I guess it is ok as long as I don't answer. Wait, I have been answering myself. hmmmm
    Last edited: Oct 11, 2012
  15. Randy_H

    Randy_H New Member


    Cranked it up and let it warm up today.....drove around the block a couple of times and it started missing again (I could feel it scan tool did not report it). No check engine light.

    I had a friend bring me a good PCM.....I changed it. Drove it to town and it missed the whole way there. On the way home the engine light came on with the following codes:

    I am going to replace the Ignition Control Module tomorrow.

    Anyone want to buy a truck? lol
  16. MrShorty

    MrShorty Moderator

    My code list suggests that P0341 indicates some fault in the cam position sensor circuit. I know you said that you replaced the CAMP and got the cam retard set right, but this code doesn't seem to go away. Assuming the new CAMP is good, I'd start checking the rest of the CAMP circuit for a break/loose connection.
  17. Randy_H

    Randy_H New Member


    soooooooooo........I am left with 1 code P0340 (cam retard is at -45 and it will not move no matter what I do)

    I have:
    changed PCM (from junkyard...same result with original PCM)
    changed entire distributor with a new one
    new plug wires
    new plugs
    new crank position sensor
    new temp sending sensors (both of them)
    new battery
    new ground cable
    new positive cable
    new spider injectors
    new thermostat
    new timing set (both gears and chain)
    new main fuse

    So after some research I have read that some GMs require a CASE relearn if you change the crank, CPS, or PCM.

    The question I cannot get answered is, did the requirement start in 1996 or 1998? Despite what people are telling me the PCMs for 96-97 are the same and the ones for 98-99 are the same but 96-97 and 98-99 are not the same. I have read that it started in 1996 and i have read that it started in 1998.
  18. Randy_H

    Randy_H New Member


    very long story short.....

    1. buy only GM replacement distributor (not the brand new aftermarket)
    2. align distributor correctly (which I did)
    3. remove both battery wires for 20 seconds and then hole them together for 10 seconds (yep, beats me but this is the only way I could get the PCM to reset from the -45 cam retard) GM mechanic told me to do it.
    4. connect a level 2 scanner (one that will read live data, specifically cam retard)
    5. start the vehicle, read the cam retard (it needs to be with 2 degees of 0)
    6. if the retard is not within spec shut the vehicle off!! (I did not.....this was one of the main failures for me)
    7. if cam retard is less than -2 IE -15 turn the distributor counterclockwise if greater than +2 turn the distibutor clockwise
    8. restart and check cam retard....continue to adjust but always shut vehicle off prior to distributor adjustments

    walla!! all codes gone (specifically P0340 which I had) and all power restored and running great.

    FYI: the proper initial distributor position can be obtained pretty easily
    1. turn motor to TDC (you can verify with timing slot on harmonic balancer and "V" cut on timing chain cover
    2. rotor button should point to the little 8 etched in the side of the distributor (you can only see it with the cap off)
    3. cap should end up with spark towers perpindicular to the motor line (crank)

    I know this may be more info than anyone wanted or wants......but if I could have come upon a couple of these steps somewhere, I would have been able to set the timing right the first time instead of the 50th. :)

    Also, throughout this post I put trouble code P0304 and I meant to type P0340.

    I would also like to thank O'Reilly auto parts and the 3 employees that helped me with a ton with parts and patience!!
    Last edited: Oct 18, 2012
  19. MrShorty

    MrShorty Moderator

    Thanks for that description. I had never heard the need to turn the motor off when adjusting the cam retard, so that could be good information for others who need to tackle this operation.
  20. Randy_H

    Randy_H New Member

    I know that's the main thing that caused my entire problem. I have never heard of such a thing.....on all of google there was only one mechanic that mentioned it. One mechanic even instructed to unplug some mystery wire under passengers side dash (brown or tan) but I couldn't find it.

    I tested the theory. I wanted to confirm the fix....and sure enough.....either distributor and or pcm combo I tried....if I follow the steps above no code.....don't follow the steps and code every time.

    Thanks everyone!

Share This Page