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Thread: NOOB constant Full knock retard I NEED Help

  1. #1
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    NOOB constant Full knock retard I NEED Help

    94 s10 blazer W vin 4wd 4dr 4.3 ecm # 16168625 16179571
    i have aldl usb and tuner pro 5.0 to pull data .
    data stream shows full retard on start up constantly starts at 24ish and works it way up to 26
    fuel trims/spark advance erratic
    timing light shows jumping at 2000 rpm
    0 deg timing in base holds steady
    has a1yr old richporter gm23 distributer
    i have tried blazer forum and s10 forum and i getting nowhere.
    i was trying to get someone to look at my logs but had no bites. so im here . idk how to load a log on to the forum .
    anyone familiar with the 4.3s my computer and what would cause this knock retard issue?
    the only thing i can find that differs from my brothers blazer logs is the knock retard his has a refurbed motor that runs great and passes smog
    Last edited by 94s10blazin; 09-20-2015 at 09:15 PM.

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    Fuel Injected! Dr_Grip's Avatar
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    Do you have a knock sensor? If not is the knock sensor cable (dark blue, B15) connected to a ground wire? If yes, have you checked the wiring and the sensor itself?

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    wow dr that's the fastest response ever for me thx. fixed the text color , yes i believe it was blue i tested between ecu connector and both sensors for continuity and tested fine . i guess just put a probe in socket and another to chassis just to check for ground just to make sure ?

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    sorry yes i have two knock sensors and i just double checked to see if it was grounded and its not i tested from ecu connector to battery
    Quote Originally Posted by Dr_Grip View Post
    Do you have a knock sensor? If not is the knock sensor cable (dark blue, B15) connected to a ground wire? If yes, have you checked the wiring and the sensor itself?

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    Fuel Injected! sturgillbd's Avatar
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    Make sure the knock sensor wires are well away from the spark plug wires etc. Electrical noise will drive the knock circuit crazy. The 94 engines had a balance shaft which can become quite noisy at higher mileages. Is the engine quiet when running? The 4.3 with two knock sensors have different knock sensors than the V8 with one sensor. If I recall correctly, they are 8K ohms and when wired in parallel, the PCM sees close to 4k ohms.

  6. #6
    Fuel Injected! Dr_Grip's Avatar
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    If you bypass both knock sensors, does it still knock? That'd point to a wiring/noise problem.

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    i think the valves could use adjustment little noisy at covers i'll pull both sensors connectors and check, never thought of interference would that be because of crap plug wires? and what does the ecu receives from the sensors resistance i thought they sent out voltage signal 4.5v i think .

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    on start up it jumps to 100 or so knock counts i think that's normal my bros logs seem to do the same , after that no counts so i don't think i have wiring issue , i checked wire insulation no cracks , i have also remove rusted heat shield to eliminate rattling and false knock . with only 100 knock counts and no input (with dummy light signaling knock circuit) it was still retard timing 24.6
    Last edited by 94s10blazin; 09-21-2015 at 06:13 PM.

  9. #9
    Fuel Injected! Dr_Grip's Avatar
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    If you don't see knocks the knock sensor is not the reason for the timing issue.

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    Fuel Injected! sturgillbd's Avatar
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    Make sure you are using the proper adx file for your bin. Seems like some of the cpi bins are $0D and others are $E6.

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    switched files i think you r right when i first got my files i didn't have my ecm and ecu #. but no difference in retard and it switched some vales around on dash board seems the same
    Last edited by 94s10blazin; 09-21-2015 at 11:08 PM.

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    so if the knock sensors lets say eliminated what else controles spark retard? i have swapped icm with a good one no difference

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    Fuel Injected! sturgillbd's Avatar
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    I just replayed your datalog. Code 43 is set. You have a knock sensor circuit problem. What is the BCC (4 letter code) on your memcal? Correct your knock sensor problem and reset the pcm. If you have ran the engine with the knock sensors disconnected and have not reset the PCM, this could be your problem. Here is a screenshot of the trouble codes from your log

    Brian

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    Quote Originally Posted by sturgillbd View Post
    I just replayed your datalog. Code 43 is set. You have a knock sensor circuit problem. What is the BCC (4 letter code) on your memcal? Correct your knock sensor problem and reset the pcm. If you have ran the engine with the knock sensors disconnected and have not reset the PCM, this could be your problem. Here is a screenshot of the trouble codes from your log

    Brian
    yeah probably didn't reset pcm before log they kept setting because i was disconnecting it to look for interference , im getting a fresh log today on the $E6 with rest pcm by disconnecting battery... you don't mean cpu relearn right?
    and the bcc 4 letter memcal i have no idea what your refering to at all . will post log in a few hrs

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    Fuel Injected! sturgillbd's Avatar
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    Here is a picture of a couple of memcals. The 4 letter code is either on the EPROM or on the blue cover of the memcal. Here is a pic of two different memcals showing where to look for the BCC code. The top one with the BCC code on the EPROM is AUJP. The bottom one has the BCC code on the cover and it is BMHK. The memcal is behind the cover with two screws on the PCM.

    Hope this helps,
    Brian

    EDIT: Pulling battery terminal will be the easiest way to reset the error code. There is a macro to send with tunerpro but you really need to know if your bin is $E6 or $0D first so you use the right ADX file. The PCM will relearn when you start the engine and drive it.
    Brian
    Last edited by sturgillbd; 09-22-2015 at 11:23 PM.

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