spark plug heat range question

Discussion in '1994 - 1995 Specific Tech' started by 95cobraguy, Feb 14, 2006.


  1. 95cobraguy

    95cobraguy Member

    Joined:
    Dec 23, 2005
    Messages:
    638
    Likes Received:
    1
    Trophy Points:
    19
    Location:
    Long Island, New York
    i dont know if this question belongs in our new section so i'll give it a shot. could a plug that is too cold give a problem starting on a cold day? i have autolite 3923's in my car with a vortech, victor jrs, 50lb squirters, and this thing just doesn't want to start when its cold out, and not even that cold, maybe 30 degrees or so. i crank it and it instantly loads up, plugs soaked in gas, wont idle, the whole deal. the car has a brand new chip in it, tuned with superchips software. my 80mm maf sensor was just recalibrated by the new professional mass air systems, formerly pro-m. they said the electronics were good and it just needed a recal. this is very discouraging as i'm convinced my car just doesn't like the cold. it never sees rain or now and i know our cars are more adapted to nice sunny spring and summer days but i feel like my motor needs to take advantage of this cold crisp air. anybody have any thoughts?
    #1
  2. final5-0

    final5-0 Mustang Master

    Joined:
    Apr 7, 2003
    Messages:
    6,817
    Likes Received:
    3
    Trophy Points:
    79
    Location:
    DFW Texas
    I know nothing about Superchips software
    but
    I do know there are a couple of fuel tables Ford put in the pcm that could be adjusted to help you.

    One controls the amount of fuel delivered during the crank up period before the car starts.

    The other controls the amount of fuel right after start up through a period of time or temp.

    I guess they could be thought of as the electronic verson of a choke.

    In a nutshell, your pcm thinks you got 19lb inj's
    but
    You really got inj's that are 2.5 times larger
    so
    That is where all the fuel is comming from during cold start up

    I would think your Superchip sofware could access those tables and dial some fuel out to compensate for your large injectors.

    I don't think a step or even two steps of colder plugs are causing this problem.

    btw, if you put the pedal to the floor during cranking, the fuel flow to the inj's will be shut off. Might help you!

    Grady
    #2
  3. 95cobraguy

    95cobraguy Member

    Joined:
    Dec 23, 2005
    Messages:
    638
    Likes Received:
    1
    Trophy Points:
    19
    Location:
    Long Island, New York
    well this has been an ongoing issue. when the car was at the tuner about 2 months ago he left it outside all day and when he went to pull it in at night, which was a real cold one, it did what i'm describing. he kept taking cranking fuel out through the chip and the car just didn't respond. finally, as a last resort, he swapped in an air flow meter he had on his shelf that was cal'd for 42lber's and was for a fox car. he said the car fired right up. so i drove the car home using his meter and no chip in the computer. i then sent my meter back, figuring it was no good, and they told me the calibratin was off but the electronics were good. so i get the car back to the dyno and my guy finished tuning it. all was fine until last week when this problem arose again. first time i cranked it, it loaded up, so i pulled all the plugs, which were soaked, dried them and put them back in. i then put my foot to the floor when i cranked it again and it started and it ran great for the 20 minutes or so i drove it around the neighborhood. few days later it did the same thing so instead of pulling the plugs i just floored it again and it started and idled alright, not great, until a few minutes later it just stalled and then wouldn't restart. at this point i pulled a plug and it was pretty wet and fouled. i called my tuner who just didn't have an answer. i guess i'll just have to accept the fact this thing doesn't like the cold. there is nothing jumping out at me pointing me in the right directon.
    #3
  4. final5-0

    final5-0 Mustang Master

    Joined:
    Apr 7, 2003
    Messages:
    6,817
    Likes Received:
    3
    Trophy Points:
    79
    Location:
    DFW Texas
    You say Superchip software.

    If this is the same as the SCT people, from what I've seen, they have a large network of support as they have dealers all over the country.

    I would think if your tuner can't make make any more head way with this issue, he would be able to tie into that support system that is available to him as a dealer.

    You should be able to dial back some fuel for start up.

    You don't have to put up with all that stuff.

    Grady
    #4
  5. 95cobraguy

    95cobraguy Member

    Joined:
    Dec 23, 2005
    Messages:
    638
    Likes Received:
    1
    Trophy Points:
    19
    Location:
    Long Island, New York
    thanks for the responses. this is really a headache. i totally agree with being able to dial back some fuel at startup, especially when its cold. my tuner uses the sct software for all his tuning but my car basically has a superchips chip that plugs into the computer, no handheld programmer or anything like that. he makes the changes on the chip through his labtop and then plugs the chip into my cars computer, i'm sure u know how it works. we just had a blizzard here over the weekend so the car isn't going anywhere anytime soon, it just sucks that everytime i try to start it when cold i have to worry about fouling plugs and fueling down the cylinders, which could lead to major motor problems such as contaminating oil, washing down the rings, etc.
    #5
  6. final5-0

    final5-0 Mustang Master

    Joined:
    Apr 7, 2003
    Messages:
    6,817
    Likes Received:
    3
    Trophy Points:
    79
    Location:
    DFW Texas
    I just remembered I had some SCT help info I down loaded a good while back.
    I've never really looked at it much
    but
    I got to poking around and found some stuff! :D

    I think it might be the help files for their version of self tuner
    but
    I'm not 100% sure about that! :shrug:

    anyway

    I was able to find those two fuel tables I talked about above.

    SCT calls them

    1) Fuel Crank Pulsewidth Vs ECT

    Here is a copy & paste of their definition from the help files

    First number is ECT and the second number is injector pulse width. This table determines how much the fuel injector pulses while the engine is cranking.

    2) Startup OL Air Fuel Ratio

    Here is a copy & paste of their definition from the help files

    A higher number increases fuel delivery and a lower number decreases fuel delivery.

    The tables would not copy but this does show that they are available.

    btw, if he was only working with the crank up table ...............
    I can see how you still got a prob. :)

    I posted up some detailed stuff a while back about the table that is used after start up and during warm up.

    I'm not gonna go into it all again. :nono:
    but
    I did find the post from 11-15-05 and here is a copy & paste from that post that I hope can be of some help to you. :D

    Before I start, I wanna say this stuff is from a Tweecer & EEC Tuner perspective.

    Three fixed parameters in the pcm fuel tables come into play when talking about startup.

    1) Time
    2) Load
    3) ECT

    We are dealing with two fuel tables.

    1) fuel_table_base_OL
    2) fuel_table_startup_OL

    The base table is where you see the commanded ratio and it is used during warm up conditions.

    The startup table is where you see values that are subtracted from the base table to give you a fatter ratio and time comes into play here.

    You asked about hot start conditions so lets use that as an example.

    btw, we're gonna use an unmodified j4j1 file for our little example.

    Say you've been driving around and go in the house for a while and decide to go somewhere else. When you start the car for the second time, the ECT is 180*

    Most NA h/c/i combos will idle at a load of say about .20 to .30 so we will use that load factor.

    Looking at the base table you see the pcm is commanding a ratio of 14.302 at that load value and ECT.

    Looking at the startup table in the 180* temp column at 0 to 6 seconds you see the value of 1.716. Notice as the time increases, the value decreases until finally at 40 seconds, the values in the table are no longer used.

    Here are the commanded, startup, and final ratio values

    00-06 secs cmd 14.302 startup 1.716 final ratio of 12.586
    07-10 secs cmd 14.302 startup 1.487 final ratio of 12.815
    11-20 secs cmd 14.302 startup 1.259 final ratio of 13.043
    21-40 secs cmd 14.302 startup 0.572 final ratio of 13.73

    At this point in time, you most likely go from Open Loop to Closed Loop conditions and the O2's are calling the shots to achieve the pcm's goal of 14.7 CL happiness.

    The Fix is to go to the 210 & 240 ECT columns in the startup table and zero out those entire columns. If need be, you could always play with the values in the 180* column as well.


    You are talking about colder temps
    but
    the principle is the same

    As time and temp rises

    A/F ratio gets leaner until you move to CL and the O2's command 14.7 to 1.

    I'd bet money this table is still stock or unmodified. :D

    Grady
    #6
  7. 95cobraguy

    95cobraguy Member

    Joined:
    Dec 23, 2005
    Messages:
    638
    Likes Received:
    1
    Trophy Points:
    19
    Location:
    Long Island, New York
    very interesting stuff, i do appreciate it. i do believe its either one of 2 things:
    the air flow meter that pmas (professional mass air systems) said the electronics were good in is no good or the electronics have an intermittent problem based on the fact that when my tuner replaced mine with one he had on his shelf the car started right up (which is a little odd considering the plugs were probably dripping with fuel) or there is still something very wrong with the tune as far as cranking fuel. when the weather here breaks and i can get this thing running i will be bringing it back to him. thanks for all the responses.
    #7
  8. final5-0

    final5-0 Mustang Master

    Joined:
    Apr 7, 2003
    Messages:
    6,817
    Likes Received:
    3
    Trophy Points:
    79
    Location:
    DFW Texas
    Now this info you have given is making more sense to me.

    After all, those two tables we have been talking about are quite well known
    and
    this guy is a Pro Tuner after all :D

    he's gotta know more than some Texas Hick with a laptop :rlaugh:

    Since he had no start up issues with his maf ....................

    It does kinda make one think the maf, maf cal, or the maf curve has some kind of prob. :shrug:

    Good Luck and let us know what the fix turns out to be :D

    Grady
    #8
  9. 95cobraguy

    95cobraguy Member

    Joined:
    Dec 23, 2005
    Messages:
    638
    Likes Received:
    1
    Trophy Points:
    19
    Location:
    Long Island, New York
    well here we go again. the car sat until yesterday when i went to go start it. weather conditions were wall to wall sunshine, about 42-44 degress, time was around 2:30 pm, and the car started. drove it around a bit to get gas, drove it maybe a total of 10 minutes. went to go start it today, weather conditons were cloudy, about 38 degrees, time was about 5:30 pm, and within 3 seconds of cranking no start, floods out. this was with my foot to the floor on the throttle to shut down injectors because i just had that gut feeling i was gonna have a problem. i assume it started ok yesterday because even though it was chilly out the sun was really beating down on the car keeping things warm. i called my tuner to see if i could borrow his meter to swap in place of mine so i will either get there tomorrow or friday morning. it should be a good few days coming up to test because the temp here is supposed to dip into the high 20's, low 30's. so either this meter is bad or the tune is off but what the f-ck is up with this? my car has 50lb injectors but i had the meter calibrated for 55's as per my tuners request. he said having it calibrated for a higher injector would keep the meter from pegging so he thinks that may have to be adjusted in the tune, if that even makes sense. all i know is this thing should start and idle like a brand new lexus, should it not? in the days proir to yesterday i opened up the injector harness and the other main harness in the passenger fenderwell to be certain no wires were broken, chafed, rubbing anywhere and everything looked good so i just taped everything back up nice and neat so it boils down to either that meter or the tune.
    #9
  10. CONCRETEWARFARE

    CONCRETEWARFARE New Member

    Joined:
    Apr 8, 2005
    Messages:
    211
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    NEW YORK
    I also live in ny and also have a similar problem. I do not drive my car yet but when I start it in my driveway to start working on it, it takes about 4-5 tries before it wont immediately stall. I have #30 injectors and when I put in a stock #19 maf the thing fired right up like there was never a problem. Im going to try to clean out the maf and change the plugs this weekend and see how that helps.
    #10

Share This Page