Bringing TBI and Multi Port Fuel Injection to a New Level.     EFI Conversions and Tuning! Seattle to Portland! E-mail Tuning Consultant!
Results 1 to 14 of 14

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

  1. #1
    Carb and Points!
    Join Date
    May 2018
    Age
    26
    Posts
    5

    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; 3 Days Ago at 03:31 PM. Reason: Missing info

  2. #2
    Fuel Injected!
    Join Date
    Jan 2017
    Posts
    143
    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; 1 Week Ago at 10:22 AM.

  3. #3
    Carb and Points!
    Join Date
    May 2018
    Age
    26
    Posts
    5
    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
    Fuel Injected!
    Join Date
    Jan 2017
    Posts
    143
    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
    Fuel Injected!
    Join Date
    Dec 2016
    Location
    Colorado
    Age
    33
    Posts
    98
    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
    Carb and Points!
    Join Date
    May 2018
    Age
    26
    Posts
    5
    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; 5 Days Ago at 08:03 AM.

  7. #7
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    82
    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.; 5 Days Ago at 09:21 AM.
    Jeeper
    87 sjimmy 4.5L /nv1500/ 8.8 3.55 rear/disc brakes.

  8. #8
    Fuel Injected!
    Join Date
    Jan 2017
    Posts
    143
    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; 5 Days Ago at 01:18 PM.

  9. #9
    Fuel Injected!
    Join Date
    Dec 2016
    Location
    Colorado
    Age
    33
    Posts
    98
    Quote Originally Posted by stew86MCSS396 View Post
    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.
    Edit.. manual and automatic are 2 different sensors. Read different ohms. Can cause all sorts of havoc. V6 uses 2 knock sensors, v8 used the one depending on trans and that decided if your using a pcm or ecm in this year. Later years used all pcms no matter what trans.
    Last edited by Stokes1114; 5 Days Ago at 07:37 PM.

  10. #10
    Carb and Points!
    Join Date
    May 2018
    Age
    26
    Posts
    5
    I’ll have to respond to all of this in the morning and try to test the knock sensor resistance in the afternoon! Thanks for keeping the didcussion alive.

    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. The best estimate I have is that it’s a brand new O’Reilly’s brand 1995 TBI 5.7L fuel pump.
    Last edited by Coopesam; 3 Days Ago at 03:29 PM.

  11. #11
    Fuel Injected!
    Join Date
    Jan 2017
    Posts
    143
    Going back to your first post, did you and pops do anything to the 350 that would make anything other than stock? ie camshaft, headers Was anything borrowed from the 4.3l particularly the throttle body w injectors? What I'm alluding to is if your engine is bone stock and you're using the correct 350 throttle body, you shouldn't be seeing those lean BLMs of 145-160 and it's a physical/mechanical condition rather than a tuning issue.
    Last edited by stew86MCSS396; 4 Days Ago at 12:26 PM.

  12. #12
    Carb and Points!
    Join Date
    May 2018
    Age
    26
    Posts
    5
    Quote Originally Posted by S.O.B.B. View Post
    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.
    So originally the V6 had the linear stepper motor type EGR valve. That we left on the the V6 and got ahold of a brand new one of these which I think might be the EVRV that you mention, though I'm not sure of the difference. We wired up the EVRV(/solenoid?) as indicated on this wiring diagram which shows both of those on the same system, wired to the same pin on the ECM. I don't have the official GM diagram for my motor, so maybe finding that would help.

    Quote Originally Posted by stew86MCSS396 View Post
    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

    On second thought having the esc on the memcal vs escm may have a lot to do it.
    Can I ask what an ESC or ESCM is? I think I know the MEMCAL to be the small blue container with the EPROM chip in it but all this time I thought the rest of the circuitry inside the MEMCAL is just analog limp-home-mode circuits. At any rate, this resistance test is very good to know. I have been working too much this week to check right away, but as soon as I'm home for the weekend I'll give that a look and see what resistance I measure.

    Quote Originally Posted by Stokes1114 View Post
    Edit.. manual and automatic are 2 different sensors. Read different ohms. Can cause all sorts of havoc. V6 uses 2 knock sensors, v8 used the one depending on trans and that decided if your using a pcm or ecm in this year. Later years used all pcms no matter what trans.
    Interesting, I'm still new enough to this field that prior to your reply, I didn't know the difference between a PCM and an ECM and have been using those words interchangeably. Since I'm using the 8625 computer, does that mean I have an ECM, and the 16197427 computer we have on the shelf at home is a PCM? Is there any reason I'd expect that computer to be the appropriate driver for my setup?

    Quote Originally Posted by stew86MCSS396 View Post
    Going back to your first post, did you and pops do anything to the 350 that would make anything other than stock? ie camshaft, headers Was anything borrowed from the 4.3l particularly the throttle body w injectors? What I'm alluding to is if your engine is bone stock and you're using the correct 350 throttle body, you shouldn't be seeing those lean BLMs of 145-160 and it's a physical/mechanical condition rather than a tuning issue.
    Thanks for giving such helpful guiding questions! I'm not sure the most logical way to put the response together, so I apologize if how I organize the information is hard to piece together the whole picture. So, we didn't try to make it anything other than stock, but it has been pieced together with some of the documentation is missing meaning it's definitely not perfectly stock. We got the long block, without the intake from my Dad's friend who had the motor rebuilt for some other project, potentially a hot rod of some sort. The bore has been done 0.030" over, so I guess that's an important detail. In terms of other compression factors, I'm not sure. For the cam I have an envelope but no document inside for what cam was purchased for it. So far, all the information I have on the cam is that the preset idle of 550 had a pretty noticeable miss, so I moved the idle up with the idle adjust screw on the throttle body to be right around 650 and now it's much smoother. My dad seems to think it's possible there is an RV cam in there.

    As for the origin of the intake, throttle body, and injectors, that is also somewhat of a mystery. We got those parts separately from another friend who pulled those parts off of a vehicle some 10 years prior. We rebuilt the throttle body and fuel pressure regulator using a run of the mill cheap stock rebuild kit from Advance Auto. The injectors seem to function fine, but I also have no idea what the flow is there. Come to think of it, fuel pump is a swap out from a 1993 TBI S10 Blazer for ~12-18 PSI in place of the 50+ PSI fuel pump that used to be in there for the CPI V6 we pulled out. We adapted the old CPI fuel lines with rubber hose to the throttle body, so I need to modify the tubing to put a Schrader valve test port in there to see the actual fuel pressure.

    Lastly, the swap kit I purchased came with a pair of Hedman Swap "Hedders" so the exhaust breathing is probably different and creeping into the BLM problem.

    This is what I have been thinking. The BLM's are high indicating a lean condition (right?), and the O2 sensor is usually below 600 mV, (also indicating a lean condition?), but my gas mileage is very bad. The mileage made me think that it's a false lean condition, and the vehicle has been running actually rich due to a exhaust leak before the O2 sensor. But, I fixed the major part of the leak over the weekend, and the BLM problem persists as well as the low fuel economy. There' still a small leak near the header to head flange, so I'm going to also tighten that up, but I don't think this is the source of the BLM's being high at this point. I figured next that it could be that I don't have the current fuel delivery and breathing components in the EPROM, and if I were to get that right, my BLM will stabilize and my fuel economy might get up to 18 or so mpg.

    I've attached some datalogs, but I'm not sure I've done that correctly or if they're any use at all. One corresponds to the first drive of the day where motor nearly stalls when I try to accelerate at a stoplight in the morning. It seems to be worse if the night before was colder. The other file is when it runs fine, but there is definitely a problem with the BLM values. Any help is appreciated! Thanks a ton.
    Attached Files Attached Files

  13. #13
    Fuel Injected!
    Join Date
    Jan 2017
    Posts
    143
    Electronic Spark Control Module, most ECMs use it and if you don't have one then ESC circuitry is built into the MEMCAL.

    Are you at elevation? Seems your key on engine off (koeo) MAP starts at 85 kpa.

    Looks like you're logging with EGR coming on and that's when you'll see the BLMs spike to 160. Anytime the EGR is off, BLMs seem to go back down to 135ish. Perhaps a bump in fuel pressure by making your fuel pressure regulator adjustable or search for "quarter mod." It don't look bad. I'm sure the bin could use some fine tuning but not much you can do without the chip burning capability.

  14. #14
    Fuel Injected!
    Join Date
    Dec 2016
    Location
    Colorado
    Age
    33
    Posts
    98
    Those are both pcms, meaning they can control trans as well as engine. 8625 and 7427 are pretty much identical, can run the same codes and can"usually" swap over without a glitch.

Similar Threads

  1. 88 chevy 1500 tuning issues
    By typhoonss in forum GM EFI Systems
    Replies: 16
    Last Post: 03-30-2018, 11:00 AM
  2. Replies: 1
    Last Post: 05-14-2017, 07:20 PM
  3. 7747 $42 1989 Chevy 4X4 need help tuning...FINALLY!
    By Psycho_Daleic in forum GM EFI Systems
    Replies: 16
    Last Post: 07-21-2015, 05:04 AM
  4. Replies: 15
    Last Post: 11-16-2014, 07:52 AM
  5. 1993 Chevy ˝ ton Drag truck
    By 1leg in forum GM EFI Systems
    Replies: 17
    Last Post: 02-25-2012, 01:21 PM

Tags for this Thread

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
  •