Sea Five

Ok, so i found someone on here with a very similar issue to mine, but the thread is a year old and un resolved so i'll try to explain the scenerio..

The car is a 99 C5 LS1 with 36,000 miles, M6

Headers, no cats, dual cone intake, 42 lb/hr ford green top injectors, Torquer v.2 cam on a 112 LSA, PRC .675" dual valvesprings, TSP 7.400 pushrods, AIR system deleted, NGK TR6 plugs, GMPP red wires & no changes to PCV system...

Once the car is cold started, after about 2-3 minutes it will begin to smoke very faintly from the exhaust and continue to do so until the rpms go above 1500 or so. the exhaust STINKS BAD of fuel, to the point that it sticks to your clothes and is embarrassing at stop lights.

the smoke does not smell of antifreeze, i blew a head gasket in my daily driver and i KNOW what coolant smells like when burned.

also, if you try to rev the car from it's 900 rpm idle, it has a slight hesitation before it revs, throttle response is poor from idle, but cruises very nice.

i pulled my plugs after about 100 miles, and all of them look fine except number 8, it smells of fuel, and is very tan and dark in comparison to the like new plugs of the other 7.

i did replace valve seals after the cam swap, but i never noticed this smoke until after we've played around with the tune for a few hundred miles. it really does not smell like oil. it just smells like fuel vapor and the tailpipe tips are very carboned up.

i OHM'ed the injectors and they are all a dead even 16.5 across the board.

does anyone know what could cause this? if it is tune related, just let me know what i should be on the lookout for. i can play around with it in HP tuners. i dont understand why only one plug looks very rich, otherwise id blame this on EOIT or 'end of injection timing', throwing raw fuel out the pipes which wasnt changed in this tune.

thanks for any advice!

rtpassini

anytime you dont have cats the fuel stink from exhaust is going to stick to you.

The Mountain Kat

Why is that? This fuel rich smell never existed before CATs. I have removed the CATs from several of my cars and never had a over-rich smell. That is an indication of a rich idle and one should not be using the CATs to hide a problem.

Sea Five

i agree. i'm probably overlooking many parameters with this tune. can anyone with a larger cam tell me ROUGHLY what they have edited, just to see if im missing anything?

i have the VE tables manually tuned in.
injector slope for my injectors
RAFT
added idle timing
high and low spark tables
COT set high
IAC setting (even though we technically dont have one)
decay settings
fuel trims around -2 / +3


i want to experiment with DFCO (decel fuel cutoff) to aid surging, and EOIT, or injection timing. anyone have any luck on a catless cammed NA tune?

thanks for the input!!!

tblu92

Looks like you have NOS that would explain the TR6's--otherwise those are too cold for your application--IMHO--
Is the smoke white/blueish OR black ??

Sounds like a blk overrich fuel mixture--which is tunable-
Does it smoke when starting dead cold ??
Or only after warmed ?
Did you scale your IFR correctly for the Ford 42 lb injectors ?
Remember the Ford injectors are rated at 3 bar and your ECM is scaled in 4 bar--- making the Ford 42's rated at 47-48 lbs in your tune
Someimes it helps to just turn off the DFCO on big cams---But I don't think that is your problem
LT's---they inherently cause rich fueling is " closed loop" or P/T operation becuse of the further back 02 bung locations-You can try to tune it out but you'll need a wideband to sort it out--
Things that help with LT's to correct fuel at P/T :
Lowering the 02 switching points--start by removing 100 points
Raising the Stoich to something leaner like 14.9 inrder to get it back
to 14.68
For cold starts go to the "open lop normal" table and lean it down in the
colder ECT areas and start up fuel areas
ADD some % to the "desired airflow table" Too much will cause the
idle to hang--
Add timing to the base timing "in gear" and "P/N" 2-3*
Raise the "desired idle" I would guess it should be with your cam and
M6 around 850-900 RPM
Raise the PE MAP theshold from 15 KPA to just above the KPA where
your eng. idles at ( around 55 to 70 with your cam) just a guess
Make sure your fuel trims are all "0" or slightly negative in the pre WOT
ranges
Just DISABLE the COT system--don't alter it
Check for vacuum leaks or throttle body air bridge leaks
Clean you MAF wires
Leave your MAF screen installed (if it came with one)

All i can think of rite off--hope this helps some--

Sea Five

tblu,

thank you so much for taking the time to post.i spent some more time with it today. first off, i changed plug wires JUST to see if anything was bad. then i maxed out the EOIT to 8, to see if it would help the smoking. it definitely changed the smell to a less potent, but the smoke did not change no matter what i altered. idle timing was around 25 degrees today, the fuel trims are around -2, idle is 900 rpm... i cant remember what else we tried. we re scaled the injectors with the proper data for the fords, and yes it is corrected for 58 psi.. this car will not stop smoking at idle! holding the throttle to 3,000 rpm it goes away, but as soon as i let off it smokes again. literally all i smell is fuel..im not going to rule out a mechanical issue, could i still have bad valve seals and have it not stink like oil? could i be pulling water in from anywhere and causing it to smoke? are my mufflers filled with some sort of oil causing it to burn off? they are XS power and have about 400 miles on them. im just pulling at strings at this point. its embarrassing to drive the car with it smoking and stinking.

i will try every other suggestion you named. the funny thing is the car has POWER and accellerates EXCELLENT! just has a decel surge issue and it smokes and stinks at idle!

tblu92

Is ther any color to the smoke ?????
Black-blue- gray-- or white ?

Have someone hold their hand over the tailpipe while you rev it up when smoking and see if you get any moisture on your hand---make sure the car is warmed up well as it is common to get some condensation moisture when 1st started cold
Do you have a catch can ???or something similar ?
LS engines are known for having horrible PCV systems--thats whay many people go the catch can route---
Take the T-Body air bridge OFF and hold the blade wide open as best you can--OR take the Tbody off completely (may be easier) and look into your intake manifold with a flashlight---See how oily it is in there-
prepared to be shocked !!!
You may have a pluugged or failing PCV system--Try taking OFF the oil cap and running it (vents the crankcase to atmosphere by-passing the PCV )even try unplugging the actual PVC valve--give it some time to run and clear up---If the system is plugged--it should clear up the smoke after a while and it would point to ypir PCV system
This would only be for white or oil fouling smoke---
Black smoke is something else
If you use Mobil one or any synthetic oil it is easy to confuse gas smells from the exhaust from oil smells--

Sea Five

Is ther any color to the smoke ?????
Black-blue- gray-- or white ?

the smoke is a haze, like a greyish white.. dissipates quickly, but smells of fuel.

Have someone hold their hand over the tailpipe while you rev it up when smoking and see if you get any moisture on your hand---make sure the car is warmed up well as it is common to get some condensation moisture when 1st started cold

i did this myself once very warm.. i dont get moisture on my hand, but my hand then stinks...like a normal un catted car.


Do you have a catch can ???or something similar ?

i have no changes to the stock 99 PCV system, and no catch can.

LS engines are known for having horrible PCV systems--thats whay many people go the catch can route---
Take the T-Body air bridge OFF and hold the blade wide open as best you can--OR take the Tbody off completely (may be easier) and look into your intake manifold with a flashlight---See how oily it is in there-
prepared to be shocked !!!

i had the tb off to polish the exterior, it is a mess in there but is normal

You may have a pluugged or failing PCV system--Try taking OFF the oil cap and running it (vents the crankcase to atmosphere by-passing the PCV )even try unplugging the actual PVC valve--give it some time to run and clear up---If the system is plugged--it should clear up the smoke after a while and it would point to ypir PCV system

I havent taken the cap off yet, ill try it in a few hours after work.. i did plug the vac line on the intake and remove the pcv valve, but i only let it idle like this for a few minutes at most..no change in smoke...

This would only be for white or oil fouling smoke---
Black smoke is something else
If you use Mobil one or any synthetic oil it is easy to confuse gas smells from the exhaust from oil smells--

I DO use mobil1 5w30.


i attempted to take a video of the smoking exhaust on my Iphone cell camera. i could visibly see the haze and smoke coming out the exhaust, but the camera did not pick up a trace of it at all!

Sea Five

ok so:

today i removed the pcv valve and plugged the intake vacuum port as to not draw in from the pcv system. I also took off the oil fill cap, changed the plug wires, and inspected the spark plugs. same condition as i originally posted. i did a compression test, got a pretty healthy 190 dead cold. i started the car. the smoke started within seconds. so i waited till it was hot again. the same vapor that is coming from the tailpipes also comes out of the oil fill cap when idling with it removed, ever so slightly. after turning the car off, the smoke kind of billows around inside the tips for a few minutes.imagine someone taking a puff of a cigarette, and just opening their mouth with the smoke inside. thats how it looks. its not thick at all. in fact, if you stand to the side, you almost cant see it. if you stand directly behind it, it is very very apparent. inside the oil fill cap REEKS of fuel. it smells like i dumped gas into the fill hole almost.

the computer still thinks everything is okay, my trims are pulling a maximum of 3 at most and its just learning since the last flash yesterday. i did set a code for bank 2, sensor 1 No activity... so i watched its data. it switches lazy at idle, similar to the other bank, probably from my LT headers.. and goes from 300 to 900 mV if held at 3000 rpm. im doubting its a sensor issue, but is it worth it to replace?

perhaps the smoke im seeing is from running LEAN? i dont know how thats possible, but isnt lean smoke light in color?

maybe the right bank 02 sensor IS bad, and the computer thinks its ok, i just have it tuned rich from its false data? after all the right bank is where number 8 is and is the fattest plug out of them all...

maybe its cosmulene (spelling?) burning out from inside the new mufflers? they have a few hundred miles on them.. what would that look like?

im at my wits end...


heres a video of the smoke residing in the tips after it was quickly keyed off from hot.

http://www.youtube.com/watch?v=GnOZnKzj-ng

Sea Five

heres a video of the smoke at idle:

http://www.youtube.com/watch?v=ttz5Uus5DH8

tblu92

Deff. looks like fuel as it is grayish blk---and the inside of your tailpipes are very black
A lazy 02 will cause it to run rich --Both if it is stuck in open loop( no code will show and it indicates an 02 not working at all) and if from the LT's and the 02 is just lazy at idle-- The open loop commanded fuel varies but at ilde its usually around 14.2 --and with the LT's you end up with again something in the low 14's-
-If you have a tuner-- You can run it temporarily in true open loop and lean it down in the idle ranges( from 50* ECT on and up to 60 KPA) as a test to see if the smoke clears-
Set your closed loop temp enable to the max and that will make it stay in open loop---THEN set the fuel in the "commanded open loop fuel normal" table ( in the idle fuel ranges) to something like 15.5 and run it awhile to see if that helps the smoking--won't hurt the engine --just run it at idle for 5 mins---

edcmat-l1

This...... Run it in open loop, and lean it out at idle. Should clear right up. You can set it up to run open loop idle full time.

PS, put cats back on it.

heems27

I'm having the SAME EXACT issue with my C5 Z06 with a LG5X3 cam. I've had two seperate tuners look at my car and they can't find anything wrong with the tune. The valve seals and plugs are all OK as well. I'm literally at my wit's end with this issue because like you said it sucks to sit in traffic with smoke bellowing out from you car. If you find a solution please let me know!!

mvvette97

is your negative trims at cruise or at idle? My cammed trans am had good trims at cruise but at idle it was about -12 and it would smoke like that. I just tweaked the MAF in the idle area and now have the trims at -1 at idle. Smoke it gone and idles better also

blownnastyc5

Generally white smoke is raw unburnt fuel, worse than just black smoke from being a little rich. I dont want to get the cats no cats flame gun out, but I dont have cats on any of my cars and none smell like gas at idle, drive, any, even with 60lb injectors in the vette.

heems27

Can a bad piston ring be the guilty suspect?

vladsvtz

^ Possibly, but the OP checked the compression and it was good on all cyl.

I hate to bump somewhat an old thread but it seems that no solution was found to this? I have almost the same issue.

Start the car up, it slightly smokes (its normal from condensation and what not) but after the car is warmed up fully running about 10 minutes, there is really thin smoke coming out of tail pipes. You can barely see (I checked last night it was dark but I have a spot light in front of the garage) and once you look at the light you can see there is some smoke in the air. Its not blue or white or black its almost looks transparent (hard to explain) and the car stinks pretty bad! Its a new LS3 swap (head and cam) I just got done with, Off road x pipe, longtubes and stingers. Car was tuned right and checked on dyno and street, so the tune is spot on. I was told that the car runs slightly richer when first warming up, however not when warm. Could be the humidity also (i think it might be) because it was raining here for a few days then got super hot all of a sudden

I would also like to find out a possible solution (if any) to this problem, since its pretty annoying. The only thing that is bad that the car has very bad smell from the exhaust, you will stand by it for a minute then you will smell it on your clothes/hands.

SargeZ06

I have no CATS and cutouts and smell nothing but *** whippin's

Silnus

I'm sure the OP has the issue resolved, thus why the thread died. But for future reference and searching, I think a lazy 02 sensor was probably the culprit.

Sea Five

this issue was never resolved. it still smokes as its been for about a year now. only changes ive made to the car were a brand new ls6 intake with a catch can and its still an issue. im beginning to rule out pcv...

the car still suns solid as can be, only smokes right at idle. and alot, if the wind is blowing itll blow the smoke past my windows, its very embarrassing.

ive ran the car is straight ve mode by unplugging the maf from a dead cold startup, same poblem.

anyone else wanna take a stab at it? i see others are having the issue too, what the heck gives?! ive just been 'dealing' with it.