1st TBI Conversion Help Needed

Discussion in 'TBI & EFI Conversions' started by MtBraun, Nov 6, 2017.

  1. MtBraun

    MtBraun Supporting Member Supporting Member

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    I removed the IAC and it was pretty carboned up. Cleaned it and did the reset procedure. No change to my symptoms when engine was cold. Once it warmed up it seems to run better. It is a bit saggy where it will flat out cut out and die when cold, but at least driveable. Something's still not right though. Here's a couple of pics of my dashboard. The IAC counts look good so I'm pretty sure that's not the problem. One thing you can't see in the pictures is when I am driving and the RPM range is just off idle, my BLM drops to the 110-115 range. This tells me it is running rich, although perhaps not terribly so. At idle my BLM corrects. INT is good at all RPM ranges.

    The first picture was taken after idling for about 5 minutes, the second picture after a 10 minute ride. Note it bounced in and out of open/closed loop. This truck runs pretty cool especially in the winter.

    @1987 GMC Jimmy

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    Last edited: Jan 10, 2018
  2. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    I need to go do mine again so we can have a comparison. I like to use the digital dash because you can't see what the CTS says on the Day Dash. I know mine doesn't do as many knock counts. It does like 4 at startup, and that's about it. My timing is set just a hair advanced from factory setting, though. When I do mine, I don't get BLM or Duty Cycle. What I get are numbers that are out of this world high, but I need to do this again to see if it still does that. It's weird that it flip flops the loop status. I'm gonna say standby and let me get mine hooked up to see what's different. Oh, and @4WDKC might have some insights because he does this stuff, too.
     
  3. 4WDKC

    4WDKC Full Access Member

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    There is a big difference between simple and easy. Wide band o2 makes tunning easier and is transferable to any system so it's not wasted on this, then spent again on another setup. I have been pondering if changing the settings for open/closed loop.

    Sent from my Nexus 5X using Tapatalk
     
  4. Honky Kong jr

    Honky Kong jr Super Sarcastic Man

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    You’d can do that with TBI? That’s pretty cool.
     
  5. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Oh, yeah. It's no OBD2, but that old 165 baud ECM will tell you a lot of stuff. That's why I plug that homemade scan tool to TBI owners, especially if they have an issue they can't track down.
     
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  6. MtBraun

    MtBraun Supporting Member Supporting Member

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    Some more interesting symptoms to relate. My son tried to use the truck this morning. Ambient air temp about 0 degrees. Truck ran so crappy that he brought it home and borrowed the neighbors plow truck. Same symptoms, severe cut out off idle. When I drove the truck a couple days ago in 25 degree temps it ran good and only cut out a couple times. It seems odd that spark would be affected by a 25 degree change in temperature, so perhaps it is a air/fuel issue with the map written in the chip. I ordered a WB yesterday and should be able to hook that up this weekend.
     
  7. 4WDKC

    4WDKC Full Access Member

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    If it were in the chip it would be the same since new,

    Its really hard to see the small print on the pics, but it looks like its in open loop, running very rich check to make sure the injectors are not sticking open. At idle the the ecm ignores the o2 if i remember correctly, what are the the engine temps on the display?
     
  8. MtBraun

    MtBraun Supporting Member Supporting Member

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  9. MtBraun

    MtBraun Supporting Member Supporting Member

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    I think I can change the dashboard display to just data. I'll try that and grab some more snapshots. Since its going to be really cold the next few days I should be able to log some data and capture the cut out.
     
  10. MtBraun

    MtBraun Supporting Member Supporting Member

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    Here is some updated data. I changed the dashboard to data only. First pic is of idle after running for about 10 minutes. 2nd pic is when driving and close to when we experienced a cut out. Any no, I'm not driving, logging data, and snapping pics at the same time!

    I got the WBO2 hooked up, and whenever the truck cuts out the AF ratio jumps way up to around 16-17 which tells me is way lean.

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  11. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Oh, man. That digital dash is so much better as far as analyzing things goes. 16" of Hg, I think, is a tad low for idle running a factory cam. That reading of 3" is really strange. I did some tests with a vacuum gauge holding approximately that off idle RPM and then snapping up to it. My car idled at 19. Slow advancement of throttle yielded little change in vacuum, maybe a few inches lower after a few seconds. Snapping it quickly to that point, the lowest I could get it to go was about 6 or 7. I couldn't get it to go that low. If you had just gunned it to that RPM when you took that picture, that reading makes more sense. If you were just chugging along, that doesn't make sense and correlates with your lean condition in my mind.

    Second, I think 69*C is too cold for operating temp. That's 154*F. It looks like it was holding in that neighborhood, too, since you said it had been running a while. Something's fishy to me with that, and I don't think it's your CTS.

    Third, I'd verify your battery voltage and alternator output. 12.3 is way too low just sitting there idling. You need to 12.6 with it cold just to get going. I don't know how reliable that meter is, but that's just too low. Your second picture's voltage is nominal, though.

    I'm only going by what looks strange to me on this. It's only two brief snapshots so I could have missed the mark. Everything else looks okay from what I can tell. I'm about to hook my computer up to the Jimmy and see if I can get TunerPro fired up and respond with my dashboard. I don't think I've used my little Chinese tool since mid-2016 so hopefully it comes through for me.
     
  12. 4WDKC

    4WDKC Full Access Member

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    Have you checked for vacuum leaks already? A cracked hose or fitting could reduce the amount of vacuum the engine thinks it is seeing.

    I agree on the coolant temp, if you havent replaced the t stat with a 180 or 195 that will get your engine temps up and with the engine warm it will use the o2 to adjust afr.

    Remember thes eold alternators dont charge at full capacity till like 1500 rpm, switching to a newer alternator, and upgrading the charging wire from alt to bat can also help with this issue.
     
  13. MtBraun

    MtBraun Supporting Member Supporting Member

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    It's possible I caught that low vacuum reading when my son was trying to feather the throttle through a cut out.

    I have a new CTS so I think it's reading accurate. This thing runs really cool. And keep in mind it was -5. Even my new vehicles (2000 and newer) take FOREVER to get hot.

    Not sure on the idle voltage. I've tested the alternator numerous times and its usually around 14.

    Do you think the A/F ratio jumping to 16 at the cutout is a symptom of the engine stumbling or rather the cause of something else? It happens so sporadically I think its simply reading the A/F at time of cutout, which wouldn't be "normal."
     
  14. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    This is mine. I didn't drive it but I tried to match your RPMs as best I could, hold it, and get a couple pictures. I think my files are written incorrectly as far as calculating my injector duty cycle. No way it's that high. The BLM kinda flips around between nominal, low, and high. I don't know what's up there. Everything else seemed okay to me. The O2 sensor did this thing where when I ramped up the RPMs a little to get that second picture it just went to 0. It would go up and down a little like maybe to 18 but not in the hundreds with the constant sine pattern. I don't know what the deal is with that. Mine runs well, but it has a lot of different numbers, which is weird. Not saying it's perfect down to the nitty gritty, but it does a good job with no surging, cutting, missing, bogging, etc. What do you think @4WDKC? And in regards to the alternator, I didn't know that. Mine shows 14.1 at startup, and it dips down a little in drive and idle, but it's got a Delcotron 12si. I've seen squares with 10si alternators so I don't know what came with what or if it even matters.

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  15. MtBraun

    MtBraun Supporting Member Supporting Member

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    I checked for vacuum leaks when we set up the system and all was good. It idles nice and smooth also.

    I'll check the thermostat. I'm pretty sure we replaced it not that long ago but maybe its a bad unit.

    I've been thinking about upgrading to a higher amperage (150+) output alternator. The plow pump sucks a lot of juice.
     

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