MN JIM

I have a 95 LT1 with auto trans. I usually warm up the car for a minute or two before taking off. I live on a service drive right off the main highway. If I accelerate at a normal pace to get up to highway speed the motor will stumble and pop then accelerate normally. If I feather it I can get up to speed without a stumble. Once the motor has done it once it will be fine the rest of the day, even on a cold start.

No codes are showing and no check engine light.

THE 383 admiral

so you have a openloop. Hesitation. O2 is not in play till closed loop. SO you will need to start out & confirm. basic maintenance.

antfarmer2

After a couple min then the service road I am thinking 02s are saying goodby.

ex-x-fire

Check for low fuel pressure, a cold engine needs more fueling, so if the pressure is low you could have a stumble at cold operation.
You could have dirty injectors too.

Tom400CFI

Fuel pressure is where I would start too.

ex-x-fire

The ecm doesn't even pay attention to the o2 when it's cold.

MN JIM

I guess I will start with fuel pressure. Kind of odd that it pops almost like a backfire. I wouldn't think fuel pressure would cause that.

antfarmer2

What is your engine temp on the digital when it does it? How many miles and how old are the o2s?

MN JIM

Engine is still cold. Does not register on the temp gauge in analog. Did not try it in digital. Cat has about 57K on it. I have no idea on the age of the o2;s.

antfarmer2

So no idea the analog is all but useless look at the digital and let us know. If you think the engine is cold after a minute or two grab ahold of the exaust. And the o2s are heated on yours.

ovrebo1

I have a 92 and I'm having a similar problem. Car doesn't run right until about 150+ on the digital. Original 02's (I think) and I haven't gotten Datamaster to work yet so I don't know what the PCM sees.

antfarmer2

My 94 did the same thing I just lived with it. Strange thing once I changed the front two o2s it went away. Looking back it was about the time it would be going into closed loop. They do get old and slow. I believe they are normal maintenance others believe they last forever.

Tom400CFI

It sure can. Low fuel pressure = lean A/F ratio. A very common symptom of a too-lean A/F ratio is backfire through the intake.

I'm not saying that it's not the O2's...it may be. But ex-x-fire is right that the O2's aren't 'in the game" when the engine is cold...and fuel needs to be extra rich.

93Rubie

I agree^ and on a 95 your MAF sensor is THE MAJOR player in determining commands for the fuel injectors. The 02's are for minor adjustments in the A/F. Make sure that it is clean and dirty free.