86Camarolt1

Car was driving fine all of the sudden it starts to hesitate and stumble. been like that since. o2,coil,ICM,opti,plugs,plug wires,wp are brand new.It runs cool with a 160 stat and with the ECM being reprogrammed for cooling features. wtf

mad95z

did you have this issue before all the new parts?
This may be fuel related, can you run a scan tool while this is happening?

PGM95Z

re-check all your plug wires.. i'd bet one burnt

86Camarolt1

the car just started doing that out the blue.plug wires are fine and fuel pressure is great ! wtf! It does not do it upon idle, it does it when its driven.

FYI -opti,ICM,plugs,plug wires,coil,o2's,wp are all brand new

any suggestions?

86Camarolt1

I pulled out the spark plugs and they are black around the edges, the passenger side plugs are darker than the plugs on driver side. anyone have any suggestions

pro94lt

That sounds like what mine was doing a couple of months ago, It drove me crazy and would drive fine, idle fine and whenever you put it under a load it would act like a backfireing q-jet. After checking all the sensors, and the obvious it was the coolant temp. switch, its on the water pump, you can test it with a ohm meter to see if its in specs,well I know you can on a 94 maybe some other guys can corect me, can you test the sensors on the 95 and ups? Not sure if thats whats wrong with yours but thats how mine was runing, good luck.

86Camarolt1

i see. I forgot to say that is brand new also

foxbat

my car has been bogging and stumbling (low rpm under load) for quite while now and your suggestion is interesting. i have a digital volt meter/ohm tester. how do i do this test? what specs am i looking for?

IPrice

SES light on???

-Ivan

86Camarolt1

Coil wire from coil to distributor is good, I changed it wit another wire and same results. I changed All sprk plugs and same results. I checked ALL spark plug wires for any burned wires there were none and I replaced the TPS she is still hesitant and now she is stumbling/hesitant on idle as well

dover179

Fuel filter. Mine was doing the same thing and that took care of it. Might try it, it's cheap and good maintenance anyway.

Btw, was the opti a delco unit or a reman or what? opti could be the issue also, i've heard of bad reman units out of the box.

86Camarolt1

gas tank has been cleaned out and the fuel filter is new also. fuel pressure reads steady .The opti is a new Delco unit

86Camarolt1

this time when I checked the fp it read 39-40 psi idle and when I get on the gas it goes up to 44-45 then drops steady at 40psi, and still is hesitant

86Camarolt1

UPDATE-------

when ignition is on, fuel pressure goes to 44psi then drops to 39-40psi in 2 seconds. and begans to drop to zero in seconds. this is when the key is in the on position (car not running.)

ACE1252

If it's dropping to zero after priming, then you may have a fuel injector leak or maybe a problem with the check valve in the gas tank.

Pull the fuel rail and injectors. Prime it....see if an injector is leaking.