twistedbowtie

i just got my pcm back today. i have a 95 t-56 lt1 flat top pistons, cc 306 cam andfull bolt ons.

when i installed the pcm i started my it took forever to start. want idel ect.

is there something i might be missing?
maybe it needs to run and adjust ?

im new to this
thanks guys

96capricemgr

This is the first time the engine has been started since the rebuild right?

If so there are way too many variables, everything and anything could be suspect including the tune from pcmforless. I had enough trouble with them that I gave up and moved onto another tuner, but if this is the first start of the new engine I would not jump to the conclusion they are at fault either.

my1994z28

I was told after a tune it takes about 1 hr or 25 miles for the Pcm to learn all the settings,tps,iac,etc...Will it idle on its own?Everyone has their own way of breaking in a new motor..I would let it idle if possible for 10 min,then rev it up to 2000 rpms for 5-10 min,let it cool down for 10 min or so..re-start it and take it for about a 10-15 min ride,go back home change the oil and your done..Like I said everyone is different..I have built over 50 engines and all the rings seatted as they should.

96capricemgr

If it needs that much time and miles to learn then the tune is way off. The pcm "learns" fuel CORRECTIONS.

Injuneer

There's also a reset procedure for the idle air control..... but other than that, the PCM doesn't have all that much to "learn".... 18 pairs of long term fuel corrections.

http://shbox.com/1/4th_gen_tech2.html#iac_reset

96capricemgr

Just for clarity, I do not think Fred was arguing with me, correct me if I am wrong.

I understand there are fuel trim cells BUT the programmed fueling should be close enough that the car runs well the O2s are just used to fine tune things for actual operating conditions. They should not be expected to make changes large enough to take the engine from running badly to running well.

What you described sounds like more than IAC relearning.

Injuneer

I was directing my comments at the first quote above. Not sure what it "learns" about the TPS either.

You are 100% correct. If the tune is correct, there will only be minor adjustments for the long term fuel trims. It appears he has only experienced a starting problem and an idle problem. I don't think he is at the point where he is driving it. So the Cell 16 BLM's are the only thing that needs to be "learned" at this point. This is a bit difficult for the tuner, because he's working in the high overlap portion of the cam and it could be spitting some unburned fuel and air.

The IAC needs an initial position for starting the engine and allowing it to idle. That, I believe, is what PCM needs to know.

twistedbowtie

No this is notthe first start on this motor. The car ran and drove fine befor the tune. Just not full potential. I'm haveing problems getting the pcm to learn anything due to the car cranking and runs for 5 seconds and dies even at w.o.t I can't make it run. Thanks guys