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    Results 1 to 7 of 7
    1. #1
      Join Date
      Apr 2010
      Posts
      3

      Accel DFI tuning help - won't idle

      Hello folks, running a pre-LS engine here but my usual forum haunts lack the EFI tuning knowledge necessary for the problem at hand. If anyone can suggest other forums where I might have more luck, please let me know!


      What I've got:
      Gen I, 383ci stroker, ~11:1CR, 286XR solid roller, ~550HP
      Accel DFI v7.0, multiport sequential, four barrel throttle body
      Crank trigger (four magnets on a wheel) and dual-sync distributor

      The history:
      The block of the original build of this engine cracked and after sitting partially diassembled for about a year in my garage I recently rebuilt it exactly to its original specs, largely to avoid any tuning issues. Prior to the rebuild it ran great, started fine (maybe taking 2-3 tries when dead cold), great street manners considering its max power.

      The problem:
      Since rebuilding it has not wanted to start and will not idle below ~1500RPM. Watching CalMap on the laptop, the AFR drops off the lean end like a cliff below 1500RPM. The closed-loop correction seems to try to compensate to no avail. Above 1500-1700 it has all of the insane power I remember from before the rebuild. The idle and poor starting are just killing any ability to drive more than around the block. Pre-rebuild the "target idle" was 930RPM. During starting it feels like it is kicking back and there is occasional backfiring. It was never like that before.

      Fixes tried:
      Most recently we tried moving the hall-effect sensor closer to the magnet wheel, down to ~.030 from ~.060. I believe the prescribed range is .050-.080. This seemed to maybe buy a hundred or two lower RPM but not an obvious difference.

      Searched for vac leaks by spraying starter fluid around likely leak spots, vac ports, etc. Also capped off all non-essential vac hoses. No effect.

      Changing the tuning shouldn't be necessary as no part of the engine changed, down to the same exact head gasket. I have been messing with the idle control setup only, and I have the pre-rebuild baseline and return to it from time to time as a sanity check. No dice.

      Checked timing with light and monitored it on the laptop. Both seem to be in agreement. Hard to see with the light when it's constantly changing since idle wouldn't stabilize at 900, should recheck now that I've stabilized it at 1500.


      Suspicions:
      Sticky fuel injectors from sitting exposed in the garage and getting saw dust on them? Looking into rigging up a home cleaning setup.
      Crank trigger not perfectly aligned with TDC?
      Distributor rotation shouldn't matter (within some tolerance) for timing but maybe try rotating to see if spark timing is falling off the edge of the contact at low RPM?
      Any other sensors could have gone bad from sitting? O2? Has to be something that would only matter at idle as higher RPM tuning feels excellent.
      First battery was bad from sitting but bought a new one which didn't seem to help. Maybe alternator has gone bad, starving the whole system for electrons? New optima yellow-top coming tomorrow but don't want to put it in until I know I won't kill it. $$$

      Really feels like overly advanced timing to me the way it kicks back but don't know what could be wrong as the numbers seem fine and the crank trigger was moved block to block but never adjusted so I don't know how it could be out more than a couple degrees. Don't know how that would explain it dropping off the lean end at low RPM either.


      EFI is new to me, suddenly carbs are feeling easy! But hoping to learn and figure this out without paying for tuning time! I do have a tuning-competent friend assisting me but he is stumped also. Any help will be greatly appreciated!



    2. #2
      Join Date
      Sep 2007
      Location
      Denver
      Posts
      325
      Country Flag: United States
      Call one of the emic guys listed on Accel site for customer support. I spoke with a Dave I think was in California and was helpful. Is this a new system or been run before?. Idle Air control could be sticking open..what is Calmap telling your on that. I assumed you did the calmap throttle position calibration. Could post over on lateral-g.net since there is a couple of EMIC's that post over there and are helpful.
      David Beckstrom DVM

    3. #3
      Join Date
      Mar 2005
      Location
      Walton, NY
      Posts
      736
      My current engine build project is almost indentical to yours but with a HR cam. Also Accel DFI. I am of no help yet because my stuff is still on the bench, but curious to see how you make out!

    4. #4
      Join Date
      Mar 2013
      Location
      Boynton Beach, Florida
      Posts
      199
      Country Flag: United States
      from your post, I think you should re visit the ignition system. You need the cam sensor to trigger half way between cylinder 2 and cylinder 1 TDC compression. You said that you are using an Accel Dual Sync? If so, with the engine at TDC cylinder 1, the blue light in the distributor should have gone out and back on at that position, if un sure, remove it and rotate it by hand, or loosen hold down and rotate it conter clock wize then re do it, if correct lock it down. If you where using both syncs, in the distributor, at TDC #1 we would pull the distributor and rotate it clock wise till the blue light goes out, then continue rotating it and the next red light would light then the blue, and when the red turned off, we would re install the distributor. ( the computer looks for the light to turn off as the trigger event) At that point we would rotate the crank shaft counter clock wise to 25 degrees before TDC, this is where you should line up your crank trigger. Also you need to check the distributor rotor to make sure it is positioned to point at the cap tower of #1 wire. Now start car, on the main dash board screen of the Gen.7 you will see an ignition timing bar graph just right of center at the top. There will be a box next to it. Check the forced tiing box and put 20 in the dialog box. Now check timing with a light and it should read 20. If not make a slight adjustment till it matches. Then un check the box, timing is now synconized with the computer. Let me know if that helps....
      p.s. we will be hosting a Accel DFI class in April 19 and 20, 2013 in florida

    5. #5
      Join Date
      Apr 2010
      Posts
      3
      Worth mentioning that I didn't build it the first time so while I'm intimate with the internals the EFI setup is new to me. I'm going to recheck the distributor sync setup as I did not go through the LED process. I did mark the distributor (rotor-to-body and body to intake) and realigned in upon reassembly but I should set it up the right way. Also, not sure if I mentioned in my original post that I tried to align one of the four magnets on the trigger wheel as close as possible to #1 firing TDC, might that not be right? It has 6 possible orientations in bolting to the crank and that's one thing I didn't mark or photograph well when disassembling. I will get back as soon as I've checked these out. Running in batch will be interesting as well. Thanks so far!

      In the meantime, here's the beast:




      Can't find EMIC's on Accel's (horrible) website anymore, though I recall seeing them before.

      Woody, I think you'll like it, it had excellent street manners and just insane top end. Hope to get the whole experience again soon...

    6. #6
      Join Date
      Sep 2004
      Location
      Kettering, OH
      Posts
      537
      Maybe you got this fixed, but have you done the following:

      1. check timing with the timing locked
      2. reset your TPS limits
      3. check your IAC
      4. set your IAC so that it is only open 20% at the desired idle

      You may need to iterate on your settings to get there from 1500.
      1967 Firebird Convert, Fuel Injected 462 ci, TKO 600
      http://1967firebird.atwebpages.com

    7. #7
      Join Date
      Aug 2007
      Location
      Las Vegas, NV
      Posts
      233
      Hey there Live,

      Don't know if you are still having trouble, but if so;
      Remember, the dual sync in your car is only reading cam position, NOT crank, so any attempts to dial in the distributor as if it is sensing both the cam and crank will be futile.
      If memeory serves me correctly the initial timing should be locked down at approximately 13 degrees BTDC.
      I agree with checking the IAC and TPS settings, as well as the sensors/motor, because although both were pretty spot on previously the idle was always an issue. Adjusting the idle via the Gen 7 was one of the more frustrating aspects.

      If you need the name and number of the guy who did the final tune I'm happy to give it to you; I think he did an awesome job and probably still has the final tune in his laptop.

      Hope it works out,

      BW
      Bob W.
      1964 Plymouth Fury
      2005 Cadillac CTS-V
      Build Thread





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