Engine Loses Power

I have a 1997 Jimmy SLE 4.3 4WD. Just recently when I am slowly accelerating the truck is fine. But when I push pedal down for a fast takeoff, it feels like the transmission is slipping or the engine is hesitating. Then i push the pedal down more and it is fine. When I get up to around 45-50 mph and try to pass another car the engine or transmision will start slipping or whatever. Sometimes the SERVICE ENGINE SOON light will flash. But I thought it was transmission problem. So I checked the transmission fluid yesterday and it was almost empty. I had it rebuilt by a transmission shop 2 years ago so it shouldnt be a transmission problem. I added fluid yesterday when it was low. My 4WD also doesn't work. I was leaning toward some kind of seal the goes bwtween transmission and transfer case. I read other threads about this happening to other people. I cant remember if it was an input or output and whether it was on the trans or transfer case. Please help. Thanks.

Did adding fluid solve the transmission slipping problem?
A blinking check engine light points to a engine misfire or engine miss.
How is the tune up end or history.
Have you checked for stored codes?
Is the transfer case low or overfull on fluid?
On the 4W not working look around on here for 4W problem post.
What transfer case do you have?
AWD or the push buttons on dash?
MT

yes adding fluid temporarily fixed my problem. i had changed spark plugs and wires in august. i dont know how to check transfer case fluid can you help me out. and i already found my problem with the 4WD. i will check codes today at AZ or Advance. i will post back no.

The transfer case will have a drain plug on rear back bottom.
And almost half way up on back it will have a fill up plug.
And also a tag back thee to tell us what type transfer case.
Always use the right fluid.

alright i will look for that drain plug on the back. i have the 3-button np233 transfer case i think. so if i open the drain plug the fluid should be level with the bottom of the plug right? thanks. i think i will find extra because my gues is my transmission fluid was leaking into it.

oh yeah i forgot i got SIX codes from my computer on the truck. P0101, P0147, P0300, P1406, and the other two didnt say any code numbers. 0101 was MAF sensor CKT, 0147 was O2 Sensor Bank 1 Sensor 3, 0300 was Random/Multiple Cylinder Misfire, and 1406 was EGR Pintle Position Circuit.

With 6 codes that is the place to start.
Plus what is your tune up history?
But with that many codes clear codes and tell us what one comes back first.

well i know that the misfire is a new one because lately i can feel it and the SERVICE ENGINE SOON light flashed a few times when i was trying to pass a car. but would the O2 sensor also cause loss of performance? I know that O2 sensor is bad because i had codes cleared a couple of months ago and it cmae back. so it said Bank 1 Sensor 3 is that the last sensor after the cat converter? i will see if i can clear them then.

a bad O2 can make the engine run extremely rich and cause the missfiring that you are experiencing. i cant remember if 97 had 3 or 4 O2 sensors. take a look up under the truck and see how many you have.

well i know that the misfire is a new one because lately i can feel it and the SERVICE ENGINE SOON light flashed a few times when i was trying to pass a car. but would the O2 sensor also cause loss of performance? I know that O2 sensor is bad because i had codes cleared a couple of months ago and it cmae back. so it said Bank 1 Sensor 3 is that the last sensor after the cat converter? i will see if i can clear them then.

I think you need to get down to the basics here.
Like Good AC Delco plugs and fuel filter and air filter.
A miss fire will give a 02 sensor code or a bad 02 sensor could cause a miss fire.
Remember a code does not say replace the sensor it says check it out.
What code no were the 02 sensor codes?
Any after market stuff like a K&N filter.
How many miles on tune up?

i already changed the plugs out with new AC DELCO plugs. And the air and fuel filters are both new. The O2 Sensor code was P0147 O2 Sensoe Heater Circuit Malfunction (Bank 1 Sensor 3) MIL Requested. Thats what the printout said.

Keep a eye out for that miss fire blinking check engine light.
Clear codes and see what returns first.
And post back
The maf sensor or the egr valve can both mess things up.
Watch them real close.
The maf and egr can sometimes be cleaned.
On the 02 code check wiring and voltage on heater circuit.
Every thing has to work together.

alright well its been about a week since the service engine light has flashed. so i dont think its misfiring anymore. how can i check voltage on O2 sensor?

alright well its been about a week since the service engine light has flashed. so i dont think its misfiring anymore. how can i check voltage on O2 sensor?
Which voltage do you want to check?
A good volt/ohm meter will read out voltages.
How about you other codes?
Has any of them come back or still there?

is this sensor the last one after the cat converter? cause it said sensor 3. it also said heated so i think it's the last one. not too sure.

is this sensor the last one after the cat converter? cause it said sensor 3. it also said heated so i think it's the last one. not too sure.

Yes bank 1 sensor 3 is the rear sensor behind /rear of cat
All of them are heated 02 sensors.
But remember the heater circuit is the 12 volt ign and ground circuit for the 02 sensor heater.
Check your PM for a repair flow chart on it.
MT

okay i looked at the chart and i will have to test it when i have time. haha. but my next thing to do it check the transfer case fluid first. because back when my transmission fluid was low i think it was leaking through that seal and into the transfer case. so i think you told me there was a drain plug on the back of the transfer case. all i do is take it out and if a lot comes out then i know that seal is bad. if so how much do you think it would cost for me to take it to a garage to get it changed? thanks.

The transfer case to transmission seal will take 3-4 hrs labor plus parts.
Just make sure you get the upper plug for checking it.
The drain plug is on the bottom and fill plug is about half way up on back side of case.
Also check to see what fluid the transfer case takes.
Some use a special fluid.
Mt

well i found the cause for my power loss. i unplugged the MAF sensor to see if thats what was bogging the motor down and it was. When I unplugged it the truck ran like almost new. It took off from stops way quicker than before. So i guess i have to get another one I checked on the internet and they cost around $100. Well on Wednesday I am getting both upper ball joints chenged because my right front tire was wearing wierd. Then I will have him check transfer case fluid. I still cannot get my Four Wheel Drive to engage the front wheels.