dannyvera778

iTrader: (5)

just finsished tuning my emc from pcmforless and thought this problem would dissapear after the tune. Check engine light is on and runs real rough def misfire but once it warms up it drives awsome and check engine light goes away. Cant figure what the problem is..any suggestions?

eagle_eyes

iTrader: (3)

whats the code?

1981LT1

iTrader: (1)

a bad coolant temp sensor will cause alot of problems and most likely not throw a specific code unless its completely broken or unplugged.

eagle_eyes

iTrader: (3)

my coolant temp sensor problem made it run rich, and die after warming up...with no codes.

1981LT1

iTrader: (1)

Are you able to get the codes when the cel comes on?

torque_is_good

interesting, usually it's the other way around that the problem occurs during closed loop vs open loop as you report.

What year is the computer/engine? if 93-95 then it's OBD1 and 95-97 is OBD2.

Was it a stock LT1? which heads are on it, the iron or aluminum ones?

the engine coolant sensor is not providing input during open loop

do you still have the EGR and AIR connected?

eagle_eyes

iTrader: (3)

interesting, what else does it provide besides temperature readings? because my computer reads the temperature in closed and open loop...according to tunerpro.

torque_is_good

allow me to clarify

and not risk a pissing match

yes, I am an LT1 owner as well

that aside

on your tunerpro does it happen to tell you that you are in OPEN LOOP??

The temp sensor basically lets the computer know that you are warm and then goes into CLOSED LOOP where all the sensors are then used and the computer then uses the input to adjust AFR, timing etc

In this case, where the OP states that the car runs like crap when cold but then better when warm, we can assume that the temp sensor is working because the vehicle enters CLOSED LOOP and begins to run better. In OPEN LOOP, the car is using a prearranged setting in the PCM. In fact, you can disconnect the temp sesnor and the CEL will light, the fans kick on and the car is in OPEN LOOP. But, his issue is it runs like crap in OPEN LOOP but better once warm.

The OP is looking for guidance. On a list of top suspects the temp sensor is not on the list because the computer knows when it's warm, the car runs better as it enters CLOSED LOOP.

Could it be the MAF? maybe, disconnect it and go into speed density mode and find out

An O2 sensor- nope, they kick in at CLOSED LOOP

Could it be EVAP or even EGR, now that's a possibility. A vacuum leak would show itself warm or cold so probably not that

We need more troubleshooting

eagle_eyes

iTrader: (3)

yes it does tell me when it's in open loop and closed loop. that's the only way i knew. also, my AFR was bad when the engine was hot or cold. it ran soo rich, even when first turned on, that the tailpipes smoked with fuel. i fixed the sensor and everything was fine. the only reason mine died once warm is the idle dropped down like it should, but because it was rich, it died.

i don't mean to sound contradicting, but to me it would seem the temp sensor fed the ECM the information it needed to adjust the fuel in open and closed loop. i don't know if my OBDI, speed density, chip ECM has anything to do with that or not...

you are right about the other options though. MAF is what i was thinking to, but a code would be nice.

dannyvera778

iTrader: (5)

no codes its not stock but an 94 lt1 ecm...i was thinking the MAF but wouldnt the check engine light stay on? I eliminatied the AIR and the EGR thourhg the ecm...is there a way to get the code by making the check engine light blink? and when it warms up extra smoke out the exhaust i thinkn it is running rich

torque_is_good

an LT1 will run rich when in open loop by design. Then, when it reaches closed loop the O2's are supposed to provide feedback.

But, running rich and running like garbage are 2 entirely different things.

If you go to www.aldlcable.com and buy a cable it would be a wise investment. Then you can perfomr data logging and if you wish, send the file to solomon at www.lt1pcmtuning.com (no, i don't work for either place and we're not related) and he could help you for a small fee as well as send new tunes via email as you capture more logs, send them to him and he tweaks the tune. But, you have a CEL and need to capture data.

If you only had 1 year newer like I do which is a 95 computer which is OBD1 but an OBD2 connector in my F body then an Actron 9145 works and can pull codes and read data.

Also, light is bneginning to shine here

please elaborate on "not stock"

Did you change the cam?

If you did, then pcmforless, albeit a good place, was the wrong choice. You need to datalog in both open and closed loop and have a tune built based upon the capturing of data. The gentleman that i suggest can do that at a fraction of the cost of a dyno shop.

Please elaborate about "not stock" and we still don't know if you have the F body heads (aluminum) or B body heads (iron)

eagle_eyes

iTrader: (3)

ok, your profile has 355 LT1 with a 604/599 lift cam.
you definitely need a dyno tune, and not a mail order tune with those kind of mods. anything you change on the car, a mail order tune will get you rolling, but i wouldn't rely on it.

what all is in this build? injectors, rockers, springs, valves, pistons...need a lot more information if you want more input. otherwise, i'd start at a dyno tune.

torque_is_good

good lord man!! Are you really running that on a tune from pcmforless

at a minimum you need solomon but a dyno tune is best.

Yes, please provide details and if what eagle found in your profile is true, seriously, stop driving the car until you can get it tuned properly.

dannyvera778

iTrader: (5)

The lift is correct plus 1.65 roller rockers and springs of course...stock injectors and port and polished heads milled to 56cc...could the car run open loop and the check engine light is off?? Because it turns off and runs smooth man it just idles ruff till it goes into closed loop and that's when it is warmed up...I never dealt with such a big lift cam...usually run mid range cams

torque_is_good

PLease please please

get it to a dyno tuner or at least datalog and use Solomon www.lt1pcmtuning.com

and stop driving it

you really need to get it logged and tuned correctly

that cam, ported heads and STOCK INJECTORS!!!!!!!!!!!!

eagle_eyes

iTrader: (3)

yeah, you need bigger injectors to feed that beast. what about the fuel pump? is it stock?
are your pistons clearenced for the lift of the cam...depending on valves? what's the LSA of the cam?

dannyvera778

iTrader: (5)

what size injectors should i run right now there the stock 26lb injectors..what kind of fuel pump do i run with that? right now i have a walbro fuel pump..something like 225 liter per hour cant remember what exactly. dont know too much about the fuel pumps....the LSA is 113

eagle_eyes

iTrader: (3)

Walbro 255 by any chance?
the stock injectors are 24#. your injector size really depends on what all you are going to do with the car. N/A doesn't need as big of an injector as power adders. if it were me, i'd go with somewhere around 36# to 42# N/A.

the cam is going to run a little choppy at idle, especially when warming up.

dannyvera778

iTrader: (5)

yea Walbro 255(cranks up right away everytime)...could have swore that 93 camaro came with 24# and 94-97 came with 26# im pretty sure about this one but wouldnt mind a correction if im wrong. and yea the clearance for the lift was done by the machine shop...thanks for the input though i guesse im set it on a dyno and get it perfect...just got to find a budget one lol

eagle_eyes

iTrader: (3)

93's have 22# and 94-97's have 24#.
either way, 26# would still be low. i believe there are injector calculators out there, just search for one. having a larger injector than needed is ok, as long as you don't go crazy with it.

torque_is_good

www.aldlcable.com

cable costs $65

www.lt1pcmtuning.com

you will log data, send the file, he will build a tune and email it to you. You then log again until it's tweaked to run great. I believe $70

I believe a total of around $135 vs continuing to run your engine the way it is which you should not.

I now pay $35 when I need to re-tune or tweaks because I'm a returning customer.