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EZ-Efi hot start problem

Discussion in 'FAST Support Forum' started by oruna1, Feb 11, 2014.

  1. Webby

    Webby Member

    Joined:
    Sep 29, 2009
    Location:
    Southampton UK
    You should really get dizzy set with correct springs and stops so that advance only begins at your idle speed.
     
  2. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    That is what I have. MSD 8360 dist with 1 light silver spring, 1 blue spring, vac advance, 21 degree stop installed. Initial timing with vac advance disconnected 16 degrees. Total timing come in at about 2400 rpm. Vac advance is connected to the ported vac source on the Throttle body (although the port is below the butterflys).
     
  3. 67RSSS

    67RSSS New Member

    Joined:
    Mar 22, 2014
    Hey, another bad ported vacuum! My band-aid for this is shorten the link between the primary and secondary throttle shafts. This helped some, and got my primary blade closer to the port, and now it is only pulling a few degrees of timing instead of 20!
     
  4. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    Once I reconnect the vac advance I am running 25-26 deg of timing at idle. IAC is @ 18-20 in neutral and aroud 30 in gear with a 650 idle setting on the handheld. It runs great like this once I get past the idle down headache. I and also going to try a 12.9 af ratio at idle to see if that helps to correct my situation. I'll report my results. I don't get why some of the throttle bodies have the ported vac source in the correct location while others have it in the wrong location. I just read a very interesting article on ported vac and timing and the bottom line is that it is undesirable to have the vac advance connected to a correct ported vac source. It states that that was a early solution to heating the exhaust to burn unburnt fuel for polution regs prior to catalytic converters. It states it's best to connect the vac adv to full manifold vac. Since my throttle body is mis-drilled that is what I have at this point.
     
  5. Webby

    Webby Member

    Joined:
    Sep 29, 2009
    Location:
    Southampton UK
    So your vac can is giving you advance at idle? So as the revs drop real low that vac will prob reduce so reducing the advance at idle. Different cause same effect? I always bin the vac advance when I fit one of these systems.
     
  6. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    That may be true, the thing I can't figure out is why does the problem disappear once the engine gets over the initial idle down the computer calls for on the initial hot startup. Once running smoothly with no surging the throttle can be blipped, raced up , driven normally, etc. with no problem with stalling, surging, bogging etc. The engine runs correctly. If the timing vac pot was the issue wouldn't it happen all the time? This is what confuses me. The only thing I can think of is that the IAC opens and races the engine to about 1200 when first started up hot and then drops the idle trying to reach the preset idle but overshoots the drop in idle speed to where it wants to stall or almost stall. I am baffled.
     
  7. Webby

    Webby Member

    Joined:
    Sep 29, 2009
    Location:
    Southampton UK
    Well if the can is dropping the timing back below what it runs at at normal idle that will also tend to slow the idle more and the IAC may not be able to keep it running.
    I use a programmable electronic ignition with no dizzy and I have it set to advance the timing a bit below normal idle speed. The advance helps keep the idle up.
     
  8. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    I changed the throttle blade setting so I now have 10 counts at idle hot in neutral. I then recalibrated the tps and it has improved quite a bit. I might try to lower the iac a tiny bit more and see what happens but since 5 is the lowest the number will go I don't have much more to play with. I understand your idea but what doesn't make sense is once I get past the idle down I have no problems at all. There was another post on the forum by someone who had exactly the same problem but after several suggestions the post stopped with no conclusion. I have to believe the preprogrammed iac close down rate after a hot startup is something my engine just doesn't like. I must be close now. I'll report back after I use the truck this weekend.
     
    Buick455 likes this.
  9. Webby

    Webby Member

    Joined:
    Sep 29, 2009
    Location:
    Southampton UK
    Yes a bit strange that it only does it on hot start. Could be fuel in rails getting hot and causing a vapour in rails problem which then clears. Don't know if handheld would be able to show mixture going weak correctly that soon after start up?
     
  10. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    I took it for a 20 mile drive on the highway and about 5 miles around town. Shut it down and waited about 5 minutes then restarted it. Startup was fine and the idle down finally worked without stalling. I would say it is about 90% there. I am going to run it again to "blow out the cobwebs" during the week and I'll report the final results. It looks like opening the throttle blades to reduce the IAC counts to 10-15 at idle in neutral and re calibrating the TPS helped a lot. I have also richened up the idle afr to 12.7 to 1 from 13.1. I have my fingers crossed that I'm well on my way to getting it running just right. Thanks for everyones help.
     
    Last edited by a moderator: Apr 14, 2014
  11. madmike

    madmike New Member

    Joined:
    Apr 15, 2014
    Location:
    Los Angeles
    I am having the same issue. When hot and returning to the vehicle. Idle bounces around for about 10 to 15 seconds trying to find its idle. Most of the time it gets there but sometimes it stalls. Giving it throttle eliminates the issue and runs great after, but it shouldn't be like this. I think something is wrong with the distributor signal personally.
     
  12. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    I ran it for 15 miles today and stopped off for gas. When starting it up to leave the station it wasn't perfect but I guess it's about as good as it will get without some other tactic to prevent it from hunting around for 15-20 seconds trying to get to idle smoothly. At least it didn't stall.. Otherwise it runs extremely smooth and nice. This problem drives me nuts. I don't think it's the distributor. I think it's the programming of the hot idle startup rpm being too high being controlled solely by the IAC motor. If the IAC counts were set lower for the hot startup then it wouldn't have to drop as far to reach the idle. It has a higher rpm on a hot start than ice cold start which isn't necessary at all. I wish we could lower the startup IAC called for in the hot start cycle, I bet that would completely solve the problem.
     
    Last edited by a moderator: Apr 18, 2014
  13. madmike

    madmike New Member

    Joined:
    Apr 15, 2014
    Location:
    Los Angeles
    Update. I notice when I richened the fuel from 14.5 to 14.3 at idle it doesnt bounce as much. I also leaned the cruse to 14.3 from 13.5.
     
  14. oruna1

    oruna1 New Member

    Joined:
    Jul 2, 2013
    Another update. Here it is several years later, engine runs perfect but the hot start issue is still here. Starts up instantly hot, rpm drops and it falls on its face or starts heavy surges of rpm. If you put it in gear it will smooth right out and from then on is perfect again. Makes no sense to me at all. Anyone else have this and figure out the solution???
     
  15. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    The new EZ EFI handheld may solve your problem. It provides for making more accurate AF mixes at start.

    FAST part #170633
     
  16. gremlinmt

    gremlinmt Member

    Joined:
    Mar 13, 2013
    Same problem here. My theory is the high IAT causes the ECU to think it needs less fuel than it actually does. The air racing down that intake isn't 140F even if the throttle body is that hot. I've got an insulating spacer under the throttle body and the IAT come down much quicker but as long as I see the intake sensor +60 or more than actual outside air temperature I have problems. Maybe I should buy another temp sensor and mount it above the air cleaner.
     

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