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Thread: Intro: Chevy 350 TBI in a 1993 S10 4x4, tuning the bugs out

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  1. #1
    Carb and Points!
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    Intro: Chevy 350 TBI in a 1993 S10 4x4, tuning the bugs out

    Just introducing myself here but also asking a question. I’m new to the DIY vehicle maintenance and tuning world so I have limited knowledge and understanding. That said, I am trying to learn as much as I can since the money saving results are worthwile and doing the work and getting to know my vehicle are rewarding in and of itself. My first car project is my daily driver ‘93 S10 Blazer. The 4.3 was tired so my Dad and I put a rebuilt 350 TBI in it back in March. I drove it from Houston to Denver two weeks ago and she’s running fairly well, but there are some issues evident now that I’ve got it hooked up to TunerPro RT.

    The most worrying thing is that it constantly reads 20+ degrees of knock retard. Whether I’m idling or stepping on the gas, the readout only ever fluctuates between 23 and 26 degrees of knock retard. The counts readout usually stays within 70-170 knock counts, 20-50 of them being present when I start the engine. I’m pretty sure I have the right data mask since I’m using $E6 for the 16168625 ECM I have and the PROM chip “BHAR” that would be stock from a 1993 K1500 with 3.42 gears and a 350 TBI. I can’t figure this one out sadly. Could part of the issue be from an exhaust leak I have? It’s weird to me that even from the moment I start the engine from cold, it already displays 25.8 degrees or so of knock retard. It seems like it might be a real issue since the motor feels like it’s lacking torque.

    I’ve searched around for anyone who has found a solution to as serious knock retard numbers as this but my searches have turned nothing up. So far this forum looks like it’s full of super knowledgeable tuners so any help from an expert would be greatly appreciated!

    Edited to include the additional question that came up later in this thread:

    I forgot to mention in the main post that I also have a serious BLM problem. The integrator part swings around a lot but the BLM value is usually way up above 145 and 160. I’ve been keeping track of my highway fuel economy, and it isn’t so stellar around 13-15 mpg. I’ve fixed the exhaust leak for the most part, so now I’m on to brain storming what else could be causing this. Unfortunately I don’t know what injectors I have nor the actual fuel pressure from the pump. I’m going to try to install something this weekend that allows me to check that.
    Last edited by Coopesam; 05-18-2018 at 03:31 PM. Reason: Missing info

  2. #2
    Fuel Injected!
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    I hafta search this too. Iirc if it does this key on engine off, so that’s your first clue it’s nothing. You need to do something to the bin to fix it. Hopefully one of the gurus will chime in as I try to search.

    Found it: http://www.gearhead-efi.com/Fuel-Inj...o-knock-counts
    Last edited by stew86MCSS396; 05-14-2018 at 10:22 AM.

  3. #3
    Carb and Points!
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    Dude, awesome! I couldn’t find that post but I was really certain someone has asked nearly the identical question before me, and I guess that was true. Thanks for posting the link, I’ll read through it carefully and hopefully the solution is buried in there somewhere. I would also appreciate answers to this thread as well, so anyone interested in posting should know I haven’t solved it yet.

    Any tips on how I can search the forum better to find previous posts on this kind of question? Would using a timing light indicate how much real knock retard there actually is? My data output shows ~15 degrees spark advance and ~25 degrees knock retard, so would a timing light show ~10 degrees of ignition delay if the knock retard was real?

  4. #4
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    With TPRT you have the means to make changes to the bin but do you have the hardware to burn a new chip or perhaps emulate the changes? The link I posted, requires you go to the line address in a hex editor and change the bit to whatever the notes in the xdf tells you to change it to. From there you burn a new chip or upload the new bin to your emulation hardware.

    My search tip if the forum search doesn't give you stellar results is to type this in your favorite search engine: site:gearhead-efi.com followed by whatever search term you're looking for. You can do this for any other site, too. i.e. site:thirdgen.org

  5. #5
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    What knock sensor are you using? Manual and automatic are different and read differently within the pcm. The knock sensor must match what is on your chip.

  6. #6
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    Quote Originally Posted by Stokes1114 View Post
    What knock sensor are you using? Manual and automatic are different and read differently within the pcm. The knock sensor must match what is on your chip.
    Correct me if I’m wrong, I wouldn’t necessarily say manual vs auto is the deciding factor. Perhaps ECM vs PCM maybe more accurate. If at all possible try to read the resistance of the knock sensor. The 8625 is looking for 4k ohms. If it measures 100k ohms you have the wrong one.

    On second thought having the esc on the memcal vs escm may have a lot to do it.
    Last edited by stew86MCSS396; 05-16-2018 at 01:18 PM.

  7. #7
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    Quote Originally Posted by stew86MCSS396 View Post
    With TPRT you have the means to make changes to the bin but do you have the hardware to burn a new chip or perhaps emulate the changes? The link I posted, requires you go to the line address in a hex editor and change the bit to whatever the notes in the xdf tells you to change it to. From there you burn a new chip or upload the new bin to your emulation hardware.

    My search tip if the forum search doesn't give you stellar results is to type this in your favorite search engine: site:gearhead-efi.com followed by whatever search term you're looking for. You can do this for any other site, too. i.e. site:thirdgen.org
    I appreciate the search advice. I guess I knew about the site specific searching on google from work, but I never applied it to home research. Thanks.

    After reading theough that link you posted, it’s almost certainly the solution to this issue. Unfortunately I don’t have the hardware to read/edit/emulate my EPROM yet. I had a chance to interact with the Moates reader/writer before drivin the Blazer back from Houston reading 3 or 4 of the BIN’s we had access to. I’m trying to figure out what the best hardware to purchase will be, since I think emulating may make tweaking the tune a bit easier, but just replacing the EPROM in the MEMCAL with a new EEPROM and using the adapter and a stock BIN would be pretty easy. Issue is I definitely don’t know the ins and outs of tuning a car or even how to manipulate the BIN files.

    The tune definitely needs adjusting, since it is my daily driver andthe motor basically won’t go until it’s warm. It’s really a problem every morning that it nearly stalls at he first 3 traffic lights with my foot on the gas. As for what knock sensor I’m using, I’m not sure. We pieced this swap together using old parts-box parts, so there’s no saying what this knock sensor came off of. I know it’s working, at least somewhat, since it was counting up to 40,000 when I had a header collector bolt come out. I still have a little bit of an exhaust leak (short tube S10 swap headers), but now that the collectors are on tighter the counts are down below 200. I’m pretty sure most, if not all, of the remaining counts are erroneous, but they are probably causing a few degrees of knock retard nonetheless.

    Things I’m hoping to know very soon are fuel pressure at idle and while driving, to get the knock retard read out corrected, and how to get the EGR to function properly. I have somewhat strict emissions where I’m at so I need to get that back in, but it seems like as soon as I wire up the EGR solenoid (brand new) the motor runs like garbage no matter what state it’s in. The valve itself is not new, but it doesn’t seem to blackened up and I can actuate it in and out with my mouth. For now I’ve left the vacuum disconnected and have blown the valve down all the way and capped the vacuum tube in order to troubleshoot everything else. I am suspicious that maybe the return spring is no good or I have the wrong pinout for the solenoid. Additionally, I guess it’s possible it could be a problem in the chip causing these issues.
    Last edited by Coopesam; 05-16-2018 at 08:03 AM.

  8. #8
    Fuel Injected! S.O.B.B.'s Avatar
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    Did the truck originally have egr solinoid or did it have evrv. (Electronic vacuum regulating valve)reason ask is I had evrv on my 87 jimmy and after the engine. And ecm swap I wired the egr solenoid and never got it to work.after looking over wire diagrams I realists I didn't. Wire it correctly.the harness has the same wires in it but don't go to the same places.I ended up disablin egr in my bin as I don't require e test.
    Last edited by S.O.B.B.; 05-16-2018 at 09:21 AM.
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