95 trans am lt1 diagnosing poor running/ running lean

[steveo]

my timing table is a guess i've never tuned for this particular cam before.

EFI and distributors can be tuned nearly the same way, just think of your RPM rows as your base timing vs your final timing, and the curve to get there. then your MAP columns are vacuum advance on top of that.

if you made a graph of timing advance at various points of a well-designed vac advance distributor setup, it'd look kinda similar to an efi timing table.

i did look at your timing table, it's a bit cracked out for sure.

think of it this way, that cam under 40kpa will always be decellerating. so all your 'vacuum advance' only comes in on decel, except for below 1600rpm under low loads, which is way out of operating range.

look how your 50-55 map row (which i'd guess is cruising range) advances the hell out of timing up to 38 degrees, and then drop s back to 32? in driving ranges, timing should never have to decrease substantially with rpm, just level off.

lets express this a different way so you can learn about timing, if this was a distributor, how would you tune initial, final, and vacuum advance?

[zoomo]

ah i see what youre saying, how i missed that i dont know. thats basically what i was trying to do, just set the timing curve like a distributor. where as you just set your initial, maybe some added timing by vacuum advance at idle ( sometimes dont run vacuum advance depending on cam) and then you just set the timing curve to extend up to 28-38 topping out at around 3000 rpm. of course then you have the option of adding more advance at cruise with the vacuum advance. this seems to help with gas mileage. i know thats very basic and im sure you understand, and know this, but thats what i was trying to accomplish. im going to adjust the part at high vacuum at cruise. i suppose really i was thinking that was would be at idle, but i see now that i could reach those conditions at cruising as well. i think i asked already, and i know ive searched but is there any way in hell i could be missing some kind of missfire under this load/cruise/acceleration, one that was caused by something other than just the tune? when you cruise it starts to shake, feels almost like its missing, but the sound is smooth. thanks again for everything steve, i dont mean to be needy, i am doing searching i promise, its just hard to narrow things down sometimes.

[steveo]

disconnecting vacuum advance for a radical cam is always done because the vacuum advance canister can't be configured properly for the cam. in this case, you have infinite control, so not having vac advance would be silly, unless its a racecar or something and you just don't care.

you could definitely have a misfire or other problem unrelated to the tune.

i would expect the timing map i made you to have a bit of 'surge' or feel a bit weird in some areas, again, because im unfamiliar with the cam, but it shouldn't really 'bog down' or stutter or anything.

[zoomo]

that absolutely makes sense about that vacuum advance and i would love to get it configured more properly, i suppose im just trying to simplify things at them moment to get it right ha. so with all that being said im thinking strongly i must have some sort of misfire while driving. I will try some more to diagnose this. probably by pulling my optispark back off as thats about the only thing i can think of, unless the cheap ignition wires are somehow internally interfering with eachother, which ive never seen without them causing burnt spots. anyway im sorry im just thinking out loud in a way. and of course welcoming any input or criticism. ill keep yall updated on what i find, and hopefully learn a lot more about this computer tuning along the way. heres my new timing map im working on, (i know its cracked out ha, more of just a "safe" tune) but its still way better than a distributor locked at a certain degree of timing all the time hahaha. (been there done that) anyway thanks again for all the help, ill keep you posted on what i find out about the running.

Edit: just an update, ive been procrastinating today, doing a lot of reading and some adjusting in the tune. Though im still convinced i have some sort of misfire by the way the car runs. im going to eat some lunch and pull the opti spark off in about an hour or so. ill post what i find. hopefully something. thanks again for all the help

[zoomo]

Sorry to double post. Just an update removed the option spark. No visual problems. Its a new chandler motorsports unit. Any stories of the arching inside the cap or anything crazy you can't see ? What about the ICM or the coil ? Although I've seem a few stories of icms causing crazy problems it doesn't seem likely with what I'm experiencing. I'm going to leave the opti spark off for a moment as I pull the plugs to check them. Anyone who knows of any unusual visual things I should check on the opti spark let me know please and thanks :) I'll edit with the condition of the plugs when I get them out.

[steveo]

imo, that opti is chinese made junk and will give you no end of problems, whether that's the cause or not. it's not the cap and rotor that's the problem, it's the sensor.

[zoomo]

Well I honestly never thought of the optical part being the problem. I actually have an opti from a 305? That I stole the sensor from in case I ever needed a spare. I know its a cheap rigged fix that I'll have to re-do but for now I'm going to put that old gm baby lt1 optical sensor in this new housing.

[zoomo]

well thank you steve for making me take a second closer look. manufacturer error. now im frantically hunting for a replacement wheel, though i should just replace the whole distributor i know.

[steveo]

just get a real opti. they are a bitch to change and everything relies on it, so it's not a great place to use cheap Chinese parts.

[zoomo]

thanks for all the help steve and everyone! got it going good today. sorry i couldnt afford a new opti. i met a guy about an hour from here who actually gave me a "good" opti. i took the wheel out and put it in mine and she runs like a dream. uploaded a tune with some of the stuff ive learned from reading steves site about eight times and straight up copying some of the numbers from there. also used some timing tables from sexytransams file online thats supposed to be the same set up as mine. it did great. ill upload some runs tomorrow. and hopefully steve or others will be kind enough to comment. heres my tune im running now.and a play log lol thanks again for everything!!

[steveo]

right on, glad you got 'er going.

that timing table is pretty much dead stock, by the way. try running the one i wrote for you originally.

[zoomo]

ok ill try that one out. im going to upload it tonight if you respond to this. did you take a look at the corrcl? im pretty sure i copied it right off of your site. is that ok for this to start?

[steveo]

well, i'd usually leave it stock, and then change it based on how stable the integrator seems. but the settings from my site should be ok for a cam like yours.

edit: looking at your bin, the corrcl settings seem stock. the integrator delays have been increased. that's probably what you want for now. see how your BLM trims look after you log a bit. if they seem to jump all over the place without reason, then play with those settings some more.

[zoomo]

sorry for the late reply, catching up at work after spending so long trying to diagnose personal car ha. I finally got a chance to log a trip home today, looks pretty good though the blm is low at cruise, and its split pretty bad at idle. im going to do some searching tonight on how to tune that. other than that it seems good. tomorrow ill try to get some wot logs :) did two today, then realized that the record wasnt on. Also, sorry steveo i have not uploaded your timing table yet. i have full intention to, just havent had time.

[steveo]

doesn't look very good to me; your trims are all over the place. needs work. might be tuning, might be something else wrong.