drastic spark retard sometimes peaking negitive

[gmanz24]

while driving either under normal circumstances to work and back as well as under wot the car will all of a sudden jerk, so i logged it and found it to be running spark advance 22*-25*ish then all of a sudden peak down and back up again sometimes down to -10*

i dont understand what this could be im just lost on this its way odd. any help and input is appreciated thanks all

[Bill@HPTuners]

What frames should we be looking at?

[gmanz24]

i have markers near the spikes there is 4 i think

[gmanz24]

3725,5984,6089,7179

[redhotjamedjimi]

if your boosting your PE should be more 12 afr or 11.5 than 13.

[gmanz24]

im not boosting thats in the future, im n/a right now

[gmanz24]

plus thats mostly a stock tune, im running 320cc injectors and the lo pe spark was messed with a bit, and thats about it, its a 97 auto pcm with everything copied over from a 99 2.4 manual tune, its been workin great up untill the past couple weeks

[redhotjamedjimi]

Looks like those ltft's are too much when the go positive add more air.

[gmanz24]

Looks like those ltft's are too much when the go positive add more air.

.... im not askin about my fuel man, i need this spark issue fixed and my fuel is fine in my concern, also i have no wideband atm so im not gonna go messin too much with fuel, also by the looks of the spark plugs id rather not take fuel away

back to the topic at hand any other things i should try, ive tried a diff icm and coils, no change. just changed my fuel filter.. it was time, and gapped my plugs to .037. car runs fine just has that issue of the spark retard

[Hauss]

How you making out with this one? I looked at the scan. Does the engine speed "hang" when you let off of the throttle? I may have screwed up my cfg. or pids in the scanner but it looks like your rpm hangs up around 1500 even after the tps is 0% for a while. You should check dfco. When you slam the throttle shut the engine should briefly go rich and then dfco will knock it down also providing a bit a an engine braking effect. I still don't know why your rpm is way above idle after you let go of the throttle so often. What rear gears are in this thing? Also your fuel trims are fairly big, I think, and this could be band aiding a lean condition, possibly messing with your timing. You need that wide band...... Goodluck. Let me know how you make out with this one!!!!

[gmanz24]

well its a cavalier so no rear gears, but i have a 93 2.3 ho grand am tranny swapped in it, the fdr is 3.94, now i do no i need the wideband bad but, i dont see how if i was runnin lean id be gettin this kinda spark retard esp with no knock, in most cases. also i think my throttle cable is a little tight so when i let off the t/b doesnt close quite perfect.

as i said before its a mostly stock tune, i havnt touched dfco or any fuel besides changing the injector constant to work with the 320cc injectors that are in there now

maybe ill try riching it up a bit but for this situation what would be the best way i should do that just up the injector constant so all over more fuel?

thanks guys

[redhotjamedjimi]

ive had this same problem before with my truck 2.2 nd ltft shouldnt be positive. the problem only occurs when your 7-8% positive on fuel trims. dont change the constant. adding more air is adding air to the ve.

[gmanz24]

what do u suggest on the ve tho how much increase, ive never touched anything like this with fuel and im nervous doin this without a wideband i didnt plan on messin with fuel like this yet, gotta do what ya gotta do tho

[Hauss]

You keep saying you don't want to mess with fuel, and just fix the spark problem. I understand you a leary in changing things but VCM Editor keeps a history of your changes. And you do understand that timing is sometimes manipulated or removed because of "lean" conditions right? Therefore the addition of fuel in the proper place and proper amount may correct a lean condition. Or better yet calibrating the maf to read the actual air entering the engine.Lean afr, high cylinder bmep(load), high temperature,excessive advance, etc all contribute to detonation( two or more uncontrolled flame fronts crashing together within the combustion chamber causing other ignitions throughout, or turning the tops of your pistons into a grainy mountain range, or worse melting things,) or something like that anyway. If this were my car I would install a wideband and begin a full tune. Setting PE to a constant, disabling closed loop and any other multipliers, reset trims and begin tuning Maf so your commanded and actual afr match. then put it back in closed loop....there is a fairly good tuning guide on this forum somewhere..... can I get a "CO-SIGN" on this pros????

[gmanz24]

first off, alpha-n man i have no maf, the tuning is done via tps vs. rpm so its not as simple as letting the car read the correct air goin in it cuz it doesnt tune via the air goin in it, and yeah i no its lean my plugs told me so, but i do have sweet gas milage haha but i need to fix the spark drop and i didnt even think to relating the spark with it being lean.

also i just changed my linjector constant and now im guessin thats the reason of this. i changed it just before i left IL a few weeks ago and it was running fine while i was there but my tps was acting up and i had the comp hooked up so i changed the injector constant lower cuz i was thinkin i had it wrong. my pcm was a 97 and i ended up using the 99s stock constant to do my math with and it was a bit of a higher number, then when i changed it i used the 97 constant resulting in a new lower one. the car ran fine for months on the old constant so ill go back to that and see if its ok.

also ill prob do a bunch of logging and slightly tweek some ve and see how it goes

thanks a bunch all

[Hauss]

why dont' you have a maf? are you super boosted? pardon my ignorance but i dont' remember you saying what type of pcm and engine this was?????greattttttttttttt....sounds like you dont' need any help... if things were fine for months then starting happening then why "tune around it"... find out what happend.... what changed if not the tune? my only question little boy is what the hek is an alpha-n man?
(its odd how text and blogs show no emotion, ya' never know when someone is raising their voice or squinting their eyebrows, thank goodness for smileys)

goodluck gman! (i didn't know you didn't have a maf, my bad)

[Hauss]

I'm gonna google the alpha n- man thing now......

[Hauss]

Alpha-N-acetylglucosaminidase is a protein associated with Sanfilippo syndrome.........Sanfilippo syndrome, or Mucopolysaccharidosis III (MPS-III) is a rare genetic disease. This lysosomal storage disorders is due to deficiency in one of the enzymes needed to breakdown the glycosaminoglycan heparan sulfate (which is found in the extra-cellular matrix and on cell surface glycoproteins). Although undegraded heparan sulfate is the primary stored substrate, glycolipids such as gangliosides are also stored despite no genetic defect in the enzymes associated with their breakdown.

MPS-III has an incidence of approximately 1.89 per 100 000 live births. Higher rates are found in certain populations such as the Ashkenazi Jews. It is a rare disease.

WHAT THE.... WHO THE..... please tell me what an alphan n man is.!..?????

[redhotjamedjimi]

wow im blown away. anyway dont be scared adding like 10% to your whole VE tables. if not more. Those numbers are all stock so the amount of modest hp above stock is about how much u should add. (new hp/old hp) The pcm has a easier job taking away fuel than it does adding it. U must remember it wants to go lean and rich around stoich ever second so if its lean by alot it will be confused (pardon the personification).

[gmanz24]

hauss, by lookin at my tune u can see what pcm it is and by looking at my ve table u can tell it uses rpm vs. tps. there is no maf, it doesnt even use the map to tune ve.

alpha-n based tuning is tps vs. rpm. ur search is done son.

also in the hpt file u will see what year as well as car.... motor is a 2000 2.4 ld9

when i first did my injectors i thought i used the wrong constant to divide with hence i did it again but now its messed up, thats why i changed it so now im gonna go back to how i had it and up the ve like redhotjamedjimi said

i didnt even think the tune was bad cuz it seemed good all the way home but that was 600 mi of hwy cruzin. i only noticed the car messin up drivin citywise.

thanks guys ps that alpha n thing u googled was hilarious i was almost out my seat with that sh*t hahahahah.

... time to lug the pc out to the car ahhhhhhh this sucks hahaha i need a laptop(another reason i dont mess with the tune much and when i do i leave it)