i'm going nutts, just missed my dyno day, 3 pulls for 30 bones. ne ways, i have the AEM EMS and have been street tuning, when one day, i get the air/fuel flat, then out the blue, after things been running strong and perfect, i start to get miss fires, so i change my plugs and gap em to .028, nope damn problem still there. ok, ok.....so i change out the cap and rotor, seemed as if things were good for a night, did more street tuning, and damn bog/sputter/hesitation @ WOT comes back, ...soo i'm like damn, i fouled out plugs again.....NOT, i change em out again, and the same crap. i was thinking it's my coil, but if it was bad, then the car wouldn't start. i have a external coil with MSD6A

i only get it at WOT, my car drives perfect at part throttle, but when i get into boost and at WOT, it falls on it's face, and doesn't accelerate. only at WOT under boost. i can be in 2nd at 30...i floor it WOT and it's good but as soon as boost comes in, it sputters and falls on it's face. normal driving is perfect. i'm bout to start tearing out my damn hair, i can't take it ne more. it was good one day, and after that, i can't get rid of that damn grimlin, damn fugger is haunting my car. any ideas? i have the AEM UEGO, and when this happens, it'll read about 2 points leaner, i'll be at a 11:1 then it'll go to 12.5:1 or around there.

red=engine speed, green=vehicle speed, blue=o2, pink=throttle, greenish-blue=boost, yellow=timing


you can see where it happenens, right where the vertical line is, is where it happens. u can't see it, but theres a drop in rpms where the line is, like this:
4,793 - 4,770 - 4,730 - 4,715 - 4,727 - 4,773 - 4,824rpms

please help!

 

try gapping to .026. i had that same problem with the break up @boost and under wot the A/F would read leaner. ended up messing my tune trying to richen it. changed plugs and went to .026. now it pulls smooth all the way to redline.

 

i've tried gapping to .026
but nope! things were good before @ .028 gap

 

Try removing the msd and running stock ignition. I've heard of some people having problems with the msd and aem. Hope this helps.

 

My thought is to mabey check the timing, It may be retarding a little to much when it hits boost... Hope you figure it out good luck!

 

it's not the timing, my timing map has never changed, and was good before. car pulled hard before this sputter stuck its head in on my fun.

gonna try removing the MSD tho. the thing is that, i have a modded distributor cap, i had to do it, now do you guys think i can run the external coil without the MSD? or does that have to be removed to, cuz if so, off to buy another brand new cap, but if can do run with it, then i'm gonna. cant be buying all kinds of crap hoping to solve the problem.

i'm thinking maybe my coil is getting weak. duno tho, how do i test my external coil and what readings do i look for?

thanks again guys,
Byran

 

your detonationg looks like. what are you using to tune it with? are you using a real wideband o2 or some stupod autometer unit? is your a/f ratio around 12-12.5? also when was the last time you replaced the plugs? what is your compression ratios? what kind of plugs are you using?

finally as someoen stated, remove the msd system completely and use only the external coil. you DO NOT need the msd external with the aem. the aem when proerply tuend can totally controll sparking and timming as well. IT can in itself do everythign that sd an do and more. you may be having a battle with the msg and the aem pulling spark and maybe together they are pulling to much.

 

I say dump the MSD (and every MSD product ever invented) and go back to the stock ignition. I can't imagine that the MSD is configured to translate the AEM's ignition commands and vice versa. realistically, you only need one anywho. They both do the same thing, just that one is external, the other internal.

Also, as a side note, I highly highly reccomend irridium plugs. I ran them on my SCed 02GT and picked up 8ft/lbs of torque at OVER stock gap. My prior plugs were stockers whos spark blew out even at a lesser gap. It's rare that I endorse a product, but this is one exception.

 

I was having some of the same problems... Ended up that my blaster SS coil was dying a painful death... Another sign that it was dying was slow starting. After it was replaced, the car started without a pause.. before i had to crank and crank and crank it to get it going.

 

I had that problem as well...it would only do it when I got on the car into about 3rd gear ....
It did it then every time at WOT....
I had a stock ignition and ADDED an msd and coil..it felt like it helped a little ....my air fuel was dead on at 11.8-1 when it would happen and ignition timing was conservative......

Do you have a PCV valve connected? You might be blowing oil ..oil causes it to run liek **** and even detonate.....I did a few things to my car.....added a cooling fan to the radiator disconnect the pcv valve and went over everything and it hasnt broken up since...

 

my timing is conservative, like i stated before, it was doing good before and it was the same timing map. my air/fuel is a good 11:5 and jump to 12:xx something when this happens. i'm using the AEM UEGO. i'm gonna try retarding it right now, gonna take a run now just to rule that out. hopefully it is the coil. anyone know how to test it?

 

i get it weather i be in 1st 2nd or whatever. if i'm accelerating hard and in boost WOT or around WOT i'll get it. i can almost accelerate without it happening as long as i dont go WOT, but @ WOT it always happen.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">I say dump the MSD (and every MSD product ever invented) and go back to the stock ignition. I can't imagine that the MSD is configured to translate the AEM's ignition commands and vice versa. realistically, you only need one anywho. They both do the same thing, just that one is external, the other internal.</TD></TR></TABLE>

all the MSD is is a amp for ur ignition system. well it does depend on which one u have. what it suppose to do is give multiple sparks and stronger sparks. in no way will it effect the EMS. i have the MSD6A with external blaster coil.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b_ron007 &raquo;</TD></TR><TR><TD CLASS="quote">

all the MSD is is a amp for ur ignition system. well it does depend on which one u have. what it suppose to do is give multiple sparks and stronger sparks. in no way will it effect the EMS. i have the MSD6A with external blaster coil.</TD></TR></TABLE>

False. The AEM (and every other sandalone short of a Motec) only fire the coil at one interval. The MSD you have fires at multiple intervals. Do you see how this could give an innaccurate reading to your AEM when in boost? Notice that it's only in boost as well. Something is panicking when transitioning in and out of open loop and closed loop. I still say toss the MSD. Borrow a friends stock coil and see what gives.

 

1316130057 is right You dont really need msd box with standalone. I had the same problem before but like some said it could be your coil going out slowly, or your ignitor Like someone said get another stock distributor and run that w/o the msd box then let us know what happens

Good Luck!

 

Have you tested your ign leads? Maybe they are starting to break up?

 

My guess is that your AEM EMS is crapping out on you. Try logging output MAP voltage from the unit to see what it's doing. Contact AEM and describe your problem.

 

i have tested my external coil, and got 1.44oms on the primary and 9.453 oms on the secondary. waiting till weekday so i can contact the company and find out what the specs suppose to be. i need to test my igniter too.

BTW, if the MSD would cause issues with AEM EMS, wouldn't u think the AEM would say so. theres directions on the proper way to hook up the MSD to the AEM. after so much power, an upgraded ignition will become necessary. even supra's can only go soo far on stock ignitions. EMS tells the MSD to ignite, then msd throws the sparks when it suppose, but it does so with multiple sparks. anyways, i am going to try removing the MSD to see how things go. BUT the thing is, i've had my AEM EMS on for about 3-4 months and haven't had problems untill last week. hopefully it's the igniter or coil.


light green-blueish is map sensor signal/boost
red=engine speed, green=vehicle speed, blue=o2, pink=throttle, greenish-blue=boost, yellow=timing

 

GoodLuck with your diagnostic!!!

 

dont forget that retarding your timing too much will cause higher EGTS and pre ignition..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D@nnY &raquo;</TD></TR><TR><TD CLASS="quote">dont forget that retarding your timing too much will cause higher EGTS and pre ignition..</TD></TR></TABLE>

Definitely don't listen to this guy. He's wrong as hell. Also, he's the guy that stated a Dseries can't make 400hp because they can't flow enough fuel... Don't believe me? Check the thread titled "400whp on pump gas , what are the secrets tuner gurus!!"

 

yeah, i understand about timing, but this timing map has been good for the whole the time i had the EMS, so the timing map cant crap out on me.

 

i'm thinking it maybe one of two things: plug wires or the igniter. gonna have to test the igniter, bout the plug wires hmmm.... probably gonna have to buy new ones, they are about almost 4 years old. you think maybe this could be the issue? i never experienced bad plug wires.

 

It certainly could be.

 

4 years old...

Thats a mighty damn long time for some wires!!!