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Thread: aldl problems and over fueling

  1. #1
    Electronic Ignition!
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    aldl problems and over fueling

    My 89 crewcab dropped about 6 mpg over night. I just installed my rebuilt 454 and was averaging about 12mpg now I'm down to a little over 6mpg. It dumps way too much fuel at idle especially when cold. It dumps so much fuel it fills up the throttle bores. I tried buying an aldl cable and using win aldl but can only pull up maw/ip, prom a and the iac. The iac is jumping from 7 to 256. Would like to be able to see O2 and map at least. Any suggestions?

  2. #2
    Fuel Injected!
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    Was the drop in mileage right after fresh installation of the engine? If so, did you change the camshaft? What other engine mods were performed if any? Could be a temp sensor issue. You should download Tunerpro for datalogging and viewing the data stream, it is a much more capable and powerful tool in so many ways. The iac counts are likely because the excess fuel is affecting the idle and the iac is trying to control it, albeit wildly.

    Double check all the ground connections, the temp sensor and get back to us.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  3. #3
    Electronic Ignition!
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    I couldn't get tuner pro to show anything I don't think I set it up right. I had about 400 miles at around 12 mpg then the last 200 have been at 6 that's all the miles on this engine. The O2 injectors and coolant temperature sensors have about 800 miles on them. As far as mods I had a good valve job done stainless valves installed, pocket ported intake full ported exhaust, mild rv cam and edelbrock intake. Around the time milage dropped it started hesitating and stumbling right off idle. Now it's lost idle control too.

  4. #4
    Electronic Ignition!
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    got tuner pro working now im so confused

  5. #5
    Fuel Injected!
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    You are still in open loop so theres not really much feedback. The blm and int are locked until closed loop. Did you by chance install a new fuel pump, injectors, or modify any part of the fuel system? It really shouldn't be "filling the bores" with fuel. By chance is your check engine light flashing rapidly? What, if any, changes have you made to the calibration?
    If it don't fit force it, if it don't force fit f&%@ it!

  6. #6
    Electronic Ignition!
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    Made no changes to calibration no changes to anything since drop in mpg. I un plugged the map sensor first electric side no change then the vacuum side then and the truck died. I plugged vacuum line back started the truck and it is still rich but no longer filling the bores with fuel. Also it's still in open loop but the ecm sees coolant temp at 174f what else is needed to go to closed loop?

  7. #7
    Fuel Injected!
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    There is a minimum time required to enter closed loop but I think it is only 45 seconds if I remember correctly. Where is the MAP vacuum hose connected? It should be as short as possible with no dips or loops and pull off a vacuum port with manifold vacuum all the time. Have you checked to see if there are any trouble codes?

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  8. #8
    Fuel Injected!
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    Also, does the engine temp start of lower and rise to op temp or is it fixed at 174*f?
    If it don't fit force it, if it don't force fit f&%@ it!

  9. #9
    Electronic Ignition!
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    the engine temp starts lower then raises to 174. I reset the computer now it goes into closed loop still rich at idle but as soon as it goes into closed look it goes into fuel control also only goes into closed loop off idle.

  10. #10
    Fuel Injected!
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    Is this your daily driver? I can look at the bin and see what is going on as I'm unfamiliar with the 454 bins.

    Are the IAC counts still all over the place?

    Check your timing with a light and see what it's doing.

    Double check all of your grounds to the engine and from the battery.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  11. #11
    Electronic Ignition!
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    It's a driverish I ride a motorcycle daily and my wife's tahoe for most other things but I'm moving 1100 miles in a few weeks and need to do better than 6mpg unloaded. Plus I have alot of stuff I need a pick up for throughout the week. It's not that big of a deal if I can't drive it for a few days. After I reset the computer all things seem to be back to normal. Iac I got steady prior to reseting.

  12. #12
    Electronic Ignition!
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    Oh timing is normal I set at 0 with the wire disconnected.

  13. #13
    Fuel Injected!
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    According to the bin scalar, closed loop enable temp is about 140 * f so you should be good there. I would seriously start double checking all ground and power connections, check the fuel system for kinks in the lines, fuel pressure would be nice to know as well.

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

  14. #14
    Electronic Ignition!
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    Will it go into closed loop at idle?

  15. #15
    Fuel Injected!
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    I don't see anything in the scalars in the closed loop section that denotes closed loop idle but there are open loop idle items. We will assume at this point that bin is an open loop bin. Do you have the 4.10-4.56 gear set in your truck?

    Buddrow
    If it don't fit force it, if it don't force fit f&%@ it!

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