How reliable are our PCM/ECM?

[silva96]

HEY gang, has anyone out there suffering from the low rpm, skipping when engine reaches normal running temperature syndrome had any luck diagnosing problem yet?? cause i got it had it since around 84k, 90k now i think it started right around the time i took her to the dealer for an air pump recall. and i noticed they capped off one of the electrical harnesess dont know why but its hangin there i guess the newer air pump didnt have a place 4 it or they put the wrong one on my 96 what do u guys think?. ok to the story I have repaced cap& rotor ac/delco new coil new ac/delco plugs, wires taylor 8mm and today replaced ignition coil module$100 for that tiny part and she still skips like crazy the whole car shakes at a light. But the funny thing is she still runs and chirps 1st like a champ i hit 135 wit no problem and she wanted more i have an automatic by the way
fuel pressure is at 42psi fuel filter and pcv valve are new ac/delco temp sensor and sender are new i dunno were to go next what a disappointment buying the coil module and no results. so how reliable is the pcm? how could the motor not throw a code i have a code reader and there is a code 4 pretty much evryting listed in the manual. with all the $$ i spent 4 nothin i coulda dropped on some headers like i am dyin 2 any suggestions gang pls help cant afford 2 throw away more$$ also replaced egr solenoid valve and egr was cleaned it opens and closes ok sorry 4 the long story hope u all had a cold beer in hand upon reading this.my advise though 2 u all check out ur faulty parts good before spending the $$ the end.

[Steve n Seattle]

Is your fuel rail at 42psi at idle? or at idle with the vacume hose removed from the regulator?

Does this stumbling only occur at low RPMS?
Does it occur ALL the time? or just when you punch the gas hard?




If it's running, it's not the PCM. They either work or they don't, no in betweens there. plus, GM PCM's are VERY reliable units... probably out last anything else on your car (without being abused of course).

hunch: fuel pump, but need more data. :)

[silva96]

I am at 42psi at idle with the hose connected to the regulator
when i punch the gas i have no hesitation, stumbling at all
in fact the tires scream and chirps 2nd no problem. the main problem is the motor leans out when the motor reaches operating temperature so when im sittin at a light or someting the motor will skake alot, the whole car shakes but it remains to have alot of power a little loss in low rpms but after 4grand shes out. upon cold start i watch the motor and it runs smooth like i said the minute it warms up it leans out according to the air fuel
ratio gauge i doubt this is the opti do u agree?

[Steve n Seattle]

When did you last change your O2 sensors? :)

It's running fine in open loop, but once the O2's warm up and trigger closed loop mode (O2 feedback is used to trim the A/F ratio) it's starts stumbling?




The other option is that you have an intake leak somewhere that is opening up once the engine heats up. Feel the back of your intake manifold (near the EGR tube that plugs into the rear of the intake) and see if you oil seeping out the back. This is common in the LT1 intake leak... but check if the back of the engine block is covered in oil first.

[silva96]

i will check out that intake leak, but to tell u the truth i watched my motor upon cold start and it does skake a little and run a
little rough it just worsens when it warms up a little this changes
everything right? i am thinking its a bad injector or the opti its gotta be a major part.