95 trans am lt1 diagnosing poor running/ running lean

[zoomo]

Hi guys, ive been using this forum a bit as i started to build this car. though this is my first post, i want to thank everyone here for all the help.

the car
95 trans am with a 350 bored 40 over it has the stock heads and a comp 276 cam. something like 224/232. cam springs that are good for like 550 lift everything else is fairly stock, but new assembled by me so it should be correct :P . just installed the engine last week.

The problem
at "cruising " throttle , about 20-35% tps, or 0-35 % tps really. i have a huge bog, like im pulling a trailor. like your exhaust is clogged or intake is clogged.the a/f gauge reads lean at this point. as i push the accelerator it hangs in this "bogged state" until you push the pedal down somewhere past 35% tps at which point the a/f gauge jumps to rich and the car accelerates decently. The air fuel meter is a narrowband and attatched to the drivers bank factory 02 sensor which seems to be working properly. next the engine lacks power and does not want to pull at all above 4000 rpm.the a/f reads rich at this point. Now lastly. the scary part i realized tonight, that helps me diagnose the problem, but also lets me know to take action imediatly. I drove and tested for hours today. got to teh gas station only to realize my gas tank filler neck was actually hot to the touch. and exxtreme pressure buildup. although i dont have any sort of evap hooked up yet. this was clearly excessive. so this made me test something i had forgot. the exxhaust temps. the passenger bank was at 700 pretty even on all cylinders. the drivers bank was at 350 on all cylinders. of course the rest of the engine doesnt seem to be quit that hot by the coolant temps and external laser temperature readings. now for the last interesting part. and probably the problem. the passenger bank 02 is stuck at about 500 or so. although i have an understanding that i gathered somehow that if i unplug the maf the car wouldnt use the 02s to adjust fuel trim and would basically run off of the ve tables.ive been chasing this problem for days now and have removed the optispark to check, checked the plugs burning white on the right bank of course but clean on both none the less), checked the fuel pressure (its 35-40 depending on acceleration) , used a pressure gauge in the 02 hole to check exhaust pressure ( highest was about 3 psi at 4000 rpm, scared to rev much higher because of the way it bogs at that point.), i checked the resistance on the injectors ( all about 13) also tried tuning it myself ( to the tune of one fried pcm the first attempt) second attempt was a mail order tune from garrettuning on ebay. not real impressed with it, but im learnign tuning myself , have succesfully uploaded about 10 different tunes today and have a good understanding of how a car works and timing and whats too much etc. and im confident my problem is not the tune.. im sure ive tested other things but i cant remember. all the time of course not replacing the 02 i know is bad. anyway i have the 02 in my hand, waiting for my car to cool down and some of the evaporating gas fumes to float away and we will see what happens. although i have seen obd1 02 sensors do wild things, i find it hard to imagine its doing all this.


so to anyone who made it throguh that, thank you, advise or criticism is appreciated. also i will give any more info that is needed. im using tuner pro rt to log and can figure out how to upload a log if i need to. thanks in advance.

ps: im sure there are errors, im sorry, ive proof read it like four times, its late. thanks for the help!! i appreciate it so much haha

[steveo]

lets keep it simple, send me your bin and a datalog and let us have a look at what you're working with. dont even look at that narrowband o2 gauge. it's useless.


got to teh gas station only to realize my gas tank filler neck was actually hot to the touch. and exxtreme pressure buildup. although i dont have any sort of evap hooked up yet.

the evap isnt hooked up? ... what about the external vent that runs down near your diff? if it's there, it'll be fine. these f-body tanks and evap systems are designed to build up a couple pounds of pressure. nothing should make the filler neck hot, really. that could be a lack of heat shielding between the exhaust and the tank which should be resolved immediately. the fuel in the tank can get a bit warm from recirculating heat soak from the rails, though.

[zoomo]

ok sorry to be a noob, but how do i go about sending you my bin and data log? im using tuner pro rt and cats by the way. also the tank heat was a lot a lot like probably over 100 degrees at neck. all the shielding is in place, and the exhaust may or may not be stock i cant tell but its not obnoxiously close. i did not measure the exhaust temp under the car. anyway. like yous aid keep it simple. ha

[ony]

where you live may be your tank heat. some road temps will get 120-140 this time of year.

[steveo]

you said you tried to tune it yourself? post the bin file you're running right now to the forum

then do a datalog with datamster or tunerpro or whatever and post that too

[zoomo]

posted the bin and log in above post sorry, was being a noob. figured out how to do it

[steveo]

cool i'll have a look

[steveo]

your right o2 is barely working, it's stuck at reference voltage. is that where you plugged that narrowband o2 gauge into? didja splice the o2 wire or something? the o2 itself could be faulty. that needs to be addressed before going any further.

[zoomo]

narrowband is on the working 02 sensor sorry for the confusion. just replaced with a new bosch 02. going for a drive. will report back in 15 minutes or so. also did remove the battery cable while i changed 02 to hopefully reset any screwed up trims from it being bad.

[steveo]

it actually wasn't really trimming at all. or going into closed loop for very long.

[zoomo]

so even with the maf unplugged, the 02 sensor still effects the fuel trim? i was under the assumption that with the maf unplugged it would run off of the ve table. but then again taht may not be correct ha. anyway new 02 installed. drove a little seems to do a lot better. much more driveable now, i think i may have still heard it pop a couple times under acceleration. and also still the power seems low and drops off around 4000 rpm and higher. though i know the timing definetly seems high at around 40 at 4000 rpm although it doesnt seem to be retarding the timing? before the 02 sensor change, the car was nearly undrivable it would bog and miss badly anytime you tried to hold steady throttle. anyway heres some more logs

[steveo]

that's not quite how it works.

with the maf unplugged you're correct that it uses VE tables... but closed loop is an additional fueling calculation on top of either one of those.

i wrote this a while ago might clear it up for you http://fbodytech.com/tuning.html#modes

will look at your logs soon

[steveo]

in the cruising log, it doesn't even seem to make it into closed loop for some reason, but the highway one seems not too bad. your timing advance needs a bit of love (mostly due to the different cam) but it's a good start.

you should lay off the 100% throttle until it's tuned.

breaking up at high rpm might be due to the fact that someone leaned out your PE tables quite a bit. try this bin instead. i tweaked your timing table a bit too to get it closer, and a few other small things, but it still needs work.

[zoomo]

Thanks so much steveo. the cruising was actually right as i left the house. i should have clarified that, and i went to highway within about 7 minutes of driving so it may have just been getting warmed up i read you link and its very informative, though i will need to read it a few more times ha. going out to install your bin shortly. thanks again for the help and ill post the results

[zoomo]

well i went for a good long drive today. it does a lot better. seems to bog under load/cruising situations. almost feels like it starts to miss fire. is it possible im missing something here? is it possible im actually getting a missfire from a failing injector or some sort of wierd ignition misfire that we cant see in the logs well? (dont get me wrong i have checked for both these conditions very well and the injectors resistance test good, visual check and spray looks good, ignition wires are new although cheap and optispark is new from chandlermotorsports? ebay shit i know, but ive removed and inspected it and seems to be working well.)

Anyways thanks for all the help so far steve. I did not realize that i had actually found your sites in all my searching and i was already using your ee file. im very interested in learning and understanding tuning this way. i work on cars as my "career" and have a very good understanding of tuning a car, and tune a carb and a distributor. I also do a lot of laptop-based scanning/diagnostic/programming on customer cars, but everything i do is back to factory. so this is very new to me, but im starting to get a decent understanding of it i feel. and im very thankful i came across this forum, and you to hopefully help me get a better understanding. thanks again to everyone. ok so heres some log files, let me know what you think. once again thanks for everything.:popcorn:




EDIT: back again, looking at the way its bogging and popping occasionally at low rpm cruise/acceleration. wondering about the timing being too high in those situations so i was just playing with the timing curve, like i said im used to turning a distributor so its very linear, let me know if im completely out of line. thanks again

EDIT2: check the second linear timing edit, more what im thinking. also adjusted corrcl. will let you know how it works. please feel free to give me advice im doing lots of searching ha

[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.

[zoomo]

Ha I suppose I could have picked a better description. In comparison to how it was this was before running lean and like crap. Been working on a tune since last night. Added in steveos timing. Seems to be closer to what I need . as I'm getting some spark knock at take off. According to sensor at least. Also changed one if the maf tables. Not sure exactly how those work yet but somewhere along the line one was turned up to more rich I believe. Set it back to stock. Anyway I'll let y'all know more tonight. Thanks as always for the help and critiscm ha

[steveo]

leave the maf tables alone until you understand how to tune it properly

what you want to do is identify some points where the BLMS (long term trims) are particularly lower or higher than 128 at a constant throttle position. start by tuning stuff under 120 or over 135. make sure these values are from a warmed up car that has been driven for a little bit. then find the AFGS airflows where the BLM is off. lower than 128, you need to REMOVE fuel. higher than 128, you have to ADD fuel.

then go into the MAF table, find that AFGS, and raise or lower the value with multiplication. do it gradually. take the value times 1.05 for 5% more fuel, or 0.95 for 5% less fuel. this will be a small enough amount where you wont hurt anything.

after you've done that one cell, you have to smooth the adjacent cells (using the graph works well) so transitions are smooth. you want to build yourself a curve, not a straight line.

once you've done a few of these points and got it smooth again, stop, flash it, log again.

this is a caveman method compared to doing it mathematically over a very long run using things like tunerpro history tables or hand-hacked tools that i use, but it works

if you find yourself moving maf cells more than 10 or 15 percent, and the curve naturally starts to look weird, stop tuning it. you probably have some other problem.....

[zoomo]

please tell me if im understanding correct. The number on the right of the maf table is my engine air flow? im trying to understand how to adjust it. i cant find anything to relate the hz measurement to, so im assuming the other measurement is engine airflow ha

Edit put about 100 miles on it tonight. at about 40 i installed a new airfilter. may sound strange, but it was old and raggedy and it seems to have helped the blms. maybe its just driving and learning though. anyway, its holding pretty steady at about 115-117 when cruising, with slight fluctuations depending on the rpm. but at idle im running pretty bad split with about 118 and 134. it seems to be running well, and the blms have stopped jumping as much. i would load the logs but they are too long. thanks in advance

[steveo]

with a maf like that, anything in the intake tract that affects HOW the air flows, including blockage in the air filter, can affect calibration a bit.


The number on the right of the maf table is my engine air flow?

you never have knowledge of "the number on the left" which is hz or whatever. all you're doing is taking an airflow value which is IN ERROR at that particular point, and altering it slightly.

[zoomo]

drove a lot more today. the numbers seem to be about where they were last night.The blms are low, somewhere between 114 118 when steady throttle throughout the rpm range. if i accelerate of course it changes. My question is, would i be wrong in multiplying all three of the maf graphs by 0.95 to lower the fuel across the board? or where is the stopping point. i understand you say make it smooth, but is that in one of the graphs, or all three. because i see how it is smooth across all three. thanks in advance for everything.

[steveo]

it actually IS one big table.

i had to split it into three (some software splits into 4) just because tunerpro's 2D graphing zoom ability sucks, and it doesn't auto-size large 2D tables very well.

so yes, it has to be smooth across all three.


My question is, would i be wrong in multiplying all three of the maf graphs by 0.95 to lower the fuel across the board?

that'll be a good starting point.

i would still hesistate to multiply the 3rd table by that much, for safety. maybe just multiply the lowest two tables by 0.95 and the highest one by 0.98, since i doubt you have any real evidence of how your high airflow is doing.

if you can get your trims up to 124 or so on average, i'd just leave it there, and let closed loop lean it out that bit extra.

[zoomo]

well i took it on about a 1.5 hour journey each way tonight. seems the more i drive it , the closer it gets, now it hangs out around 117 120. I havent tried adjusting any maf tables yet. I was thinking maybe i should wait until i can get it on the dyno or get a wideband a/f set up. is it normal to have to lean it out for a larger cam slightly? or are you actually leaning it out, or just telling the computer that its getting more air? i can only find one tune for a car set up like mine online, and the maf ables are not changed in that tune, but who knows how exact it is.. my injectors are stock. and my cam is a 226/232 or something like that ha

[steveo]

yeah, it's normal. maf calibration at low rpm is really sketchy with a larger cam, the air pulses back and forth instead of straight in, so it'll read kinda rich.

[zoomo]

sorry i know its a huge log. mostly just cruising home but theres a few take offs. also the blm split at closed throttle seems to be the worst. but i raised the corrcl and i think thats why. maybe i need to lower it again, it seemed to be better at closed throttle that way. im also going to adjust the maf table as you suggested for the next flash. hopefully this looks more like it should, thanks for taking a look at it if you do :happy::popcorn:

[zoomo]

sorry to double post but im confuused about the maf tuning and im having a hard time finding information about it, but maybe im just searching for the wrong things. anyway, i did some highway driving today at higher rpm trying to see how the blm looks. even if im running at say 3000-3500 rpm for a few minutes on the highway with steady throttle im still showing 117 120 and sometimes lower. is this still normal with the bigger cam? im paused on tuning right now, i dont want to lean anything out if im going in the wrong direction,but i will continue if this is fairly normal. according to the narrowband running off of the stock 02 it shows its lean to stoich and rich when accelerating.

[zoomo]

OK guys help me out one more time. Got it on the dyno today. Seems decent. Power could be a little better but that's normal ha. Running lean though not much. I expected it to be rich if anything. Though it does seem to be a corrections issue. Notice the rich AF ratio. That was with the maf unplugged. Posting from my phone so sorry for errors. Let me know what you think and thanks as always

[steveo]

that isn't rich, it's VERY lean for wide open throttle. you're hitting 15:1 there, you need to be around 13:1.

[zoomo]

Sorry for the blurry pictures. Maf plugged in running 15-1 up to 4000rpm then drops down to 13.5-1 by 5000 rpm. Maf unplugged running 13.75-1 and dropping to 12.75-1 by 5000 rpm

[steveo]

your maf tables must be way off or you have a leak in the intake elbow, or the maf is dead. theres no way itll nail a better wot afr with stock ve tables better than a maf.

[zoomo]

So I tried adding 10% to the maf table all the way across. Did lower the AF but only about .5 I'm confused though I was understanding that with the blms reading low I should be removing fuel ?

[steveo]

your BLMs are reading rich in general when running a maf, but the dyno shows you being very lean at wide open throttle? that screams 'something is wrong with this picture' to me.

if your o2s are working correctly, yes, but keep in mind BLMs are only good for the range that the cell operates in.... so if you're expecting trim data from cruising to be valid at wide open throttle and high rpm.. well..

i think you have quite a bit of information that needs to be analyzed properly at this point, and stop just trying a whole bunch of different stuff trying to patch it together.

i really do think you're trying to patch a mechanical or metering problem with tuning, which is a very wrong thing to do.

so lets make sure you're running on all 8, dont have exhaust or intake leaks, your fuel pressure is solid, and all your sensors are measuring correctly.

if all those things were OK, it would NOT be doing this.

[zoomo]

believe it or not ive checked all that stuff multiple times including today. the only possible failing sensor i could see is the maf, though i dont see enough fluctuations in the readings for the to be true.

Did some more testing before leaving for the day. no matter what i do the computer corrects itself to the air fuel that you saw in the pictures. i even made a pass with the brake booster vacuum line disconnected. the highest it is getting is about 15.4-1, though it does go much lower in open loop. why is the computer correcting to this mixture? here is a drive home running a tune with 5% less on the maf scale around the cruising rpm, seems to have really helped my blms, though even with the corrcl where it should make little to no adjustments it is still split bad at idle.

Please feel free to tell me what im missing.

Edit: also wondering about doing a speed density tune for testing.
Also noticed that the current tune im using is using a stock PE correction at wot table. The one you had sent me was raised quite a bit, i assume this is raising the amount of fuel added at wot in pe mode. i assume i should use your bin for this and it may help. ha


edit added a dyno run lol

[roughneck427]

heres my tune from my old car i couldnt fine my final tune which i ended up doing 390 rwhp and forgot the tq it was a CC503 ported heads 12:1cr through mac mid tubes

[zoomo]

Thank you roughneck. I did not upload your tune but it is great comparison information.
Back at work today hooked up an 08 Mercedes to the air fuel and it reads lean at high 15s and low 16s so I assume this AF is out of calibration somehow. According to my obd2 scanned the mercedes is running perfect 14.7-1

[zoomo]

Well i think its getting close, still lacking a reliable wideband 02 reading though. after some more research and diagnosing it seems the filter is clogged and one of the pumps needs rebuilt on the dynojet wideband, which explains the lean condition, due to the lack of vacuum. I lowered the maf table by 10% in some areas and changed some timing and stuff. it seems to be running rich at idle though, i havent messed with it any. im starting to feel pretty good about it. thanks for all the help guys i really appreciate it!

[zoomo]

Well I finally got some time and new filters for the air fuel set up on the dyno. Just in case anyone ever comes across the same problem. The lean mixture was caused by the filter being slightly clogged on the intake of the dynojet air fuel assembly. I know this is somewhat off topic diagnostic for you guys but hopefully it can help someone some day.I can't thank you guys enough for all the time you spent trying to help.

So in summary if you're using a standalone wideband air fuel set up and reading abnormally lean, check out the vacuum it is pulling should be high like at least 15. And check the in line filter. Ha

[steveo]

usually i wouldn't bother even checking that, since dynos run many cars in a day, and if the wideband was screwed surely someone would have noticed by now, since every single car would be reading incurably lean. must be a pretty slow dyno if it took that long to realize.....

[zoomo]

Edit: original post was rude on my part. Thanks for the help guys, and yes it is a slow dyno it hasn't been used in a few months