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Thread: RPM drop rapidly when coming to a stop and engine wants to stall or does stall, after 116 Update

  1. #51

    Default RPM drop rapidly when coming to a stop and engine wants to stall or does stall, after 116 Update

    Desmo, Learning does not come on until ECT reaches 160 degrees F. It should stay on unless temp drops below that.

  2. #52

    Default RPM drop rapidly when coming to a stop and engine wants to stall or does stall, after 116 Update

    My 418 5 speed Saleen has the same stalling issue when coming to stops, hence why I only have 300 miles on the car since Sept 13, I am about ready to go back to a carb and be done with msd efi.

  3. #53

    Default RPM drop rapidly when coming to a stop and engine wants to stall or does stall, after 116 Update

    Stalling when coming to a stop is typical when the throttle blades have not been adjusted properly. The fine adjustment on the throttle blades should be done with the engine at operating temperature; if the vehicle has an A/C, turn it on and let the engine stabilize.

    For those with an automatic, the transmission should be in gear. Be sure to have someone hold the brake as the throttle blades are adjusted.

    As per our instructions, a general target IAC at idle is between 10-20 for a manual transmission and 5-15 (in gear) for an automatic. It is ok to have a lower (or higher) IAC as long as the engine idles at a comfortable rpm and the engine does not stall when coming to an idle.

    When the Atomic EFI is NOT controlling timing, the idle control is limited to the IAC function. The Atomic could be fighting the timing curve in the distributor, causing a RPM surge.

    For example: If the initial (idle) timing is 15° the engine is going to want to idle higher than if it was at 8°. If this rpm is higher than the Idle Target RPM in the Atomic, the throttle body will try to close the IAC to get the rpms down, then it senses a stall and opens the IAC to save it, thus causing a surge.
    This is where it is an advantage to allow the Atomic to control timing. The system can remove timing to help get to the target idle rpm.
    Of course there are other variables, that the Atomic has no control of, which can affect the idle such as the cam, intake manifold and engine combination.

    The ATOMIC EFI controls timing by using sensor inputs from MAP, TPS, O2, etc. to adjust the timing, fuel and IAC accordingly. Just like a modern EFI equipped car/truck would do.

  4. #54

    Default

    So, interesting thread here! For the first 2 years of this thread's existence the help from MSD tech was literally and utterly 10000% useless! Like beyond useless!!! Then out of nowhere in July of 2014 someone from MSD that actually sounds like they know something finally chimed in and there hasn't been a reply since!

    I'm curious, here we are in June of 2018. How many of you are having this problem? Has anyone found a fix for it?

    I just installed the EFI on my '67 Mustang, 302, .040 over, 351 stock cam/timing. Stock otherwise. I'm running a return line with the regulator in it. I turned the blade screws while watching the blades as closely as possible. Found the point that I thought they were starting to open and went 1/2 turn from there. That set my idle at about 1400rpm. I brought it back down to about 800 rpm. Took it for a spin and imagine that, I have the EXACT same issue described over and over in this thread. I started messing with the adjuster screws and found that if I had the idle around 1000 that the IAC seemed to be in spec, roughly 7-12 bouncing at idle. I took it for a spin like that and it never stalled once. Only who wants their idle set at 1000rpm???!!!

    I do not have the timing control setup yet! In the instructions it literally says to install without timing control and get it running and dialed in first. That's what I'm trying to do! I have everything needed to do the timing control but the instructions literally say not to do it until it's dialed in and running first. I already have a probillet distributor and I have the 6AL box, I've got the phased rotor sitting on the bench at home ready to go.


    So... Has anyone figured out a fix for this without timing control? Has anyone had the issue and then setup the timing control and actually had it the issue go away?


    Just like everyone else, I can double foot it and keep it running. I can't reproduce it in the garage, I can only get it to do it when driving and I actually push the clutch in to come to a stop, that's when it drops and stalls if I don't catch it in time!


    Heck, has anyone wrecked their car yet by loosing the power brakes/steering and sent MSD that bill or had them in the court dealing with the repercussions? The issue is very well known and very well documented with absolutely horrible support as mentioned continuously in this thread!

  5. #55
    Join Date
    May 2018
    Posts
    5

    Default

    I've been experiencing this issue some with my 79 Mustang, 307 with a big cam and manual transmission, no power steering, AC or brakes, this is an all manual car. I have been playing with the setup some more, reset the idle screws to 1 1/2 turns then set the IAC to around 12-15 to hold a 950 rpm idle which was as close to zero as it would stabilize for me. I'm running a pressure regulator and return line, display shows consistent 49psi, and I have timing control enabled. I did richen up the AFRs and it seems to be idling a bit better. I need to get out for another drive though to test those latest settings to see if it affected the stalling. Each time I've tweaked things, it seems to reduce the problem. I don't have a lot of drive time in on it yet, so hopefully the learning will continue to improve it as well.

  6. #56
    Join Date
    May 2018
    Location
    Hadlock, WA
    Posts
    4

    Default

    I'm still fighting it as well. Stroked 440 stick car. Just upgraded fuel system to return with MSD regulator, and Aeromotive Stealth tank with pump inside. Making me a bit crazy. Not to mention the crap from the old school buddies questioning why I went with fuel injection....

  7. #57

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    Curious, do you guys have single or dual plane intakes? I've almost got this issue tuned out on mine but it does still on occasion happen. This weekend I'm going to cut the center out of the spacer I have between the throttle body and my intake and essentially try to fake a single plane draw effectively. I've "heard" this may make a noticeable improvement...

  8. #58

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    My car took a while to learn but I recall it eventually figured out how to not stall before I was running timing control. With timing control, much better. I switched because timing control helped a lot with some part throttle issues - not to mention on the fly timing adjustments.

  9. #59
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,486

    Default

    Part of the problem is the MSD system does not look at VSS (vehicle speed) as the car is slowing down.
    Where to put the IAC as the vehicle approaches about 5mph, if we don't know the vehicle speed?
    Regards, Gary

  10. #60
    Join Date
    May 2018
    Posts
    5

    Default

    My car has not had further trouble with the stalling coming to a stop since I reworked the IAC settings. I was still having trouble with stalling after some light throttle when parking or pulling into the garage. I bumped up the timing at idle and that too is better now.

    I read about the dual plane vs single plane manifold theory too and since I'm running a dual plane (Edlebrock Perfomer Air Gap)I decided to add a 1/2' open spacer to see what it would do. I cant say I notice any significant difference so far, but it did solve my air cleaner to distributor clearance problem so at least that is a win. I did notice though that the base gasket that is supplied by MSD was an open type, so there may be something to this.

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