engine bogs down...

Ok here it is I have a 97 4.0L auto 4x4 and after it sits for a while and I go to drive it again I will back out of the driveway/parking space, put it in drive hit the gas and it will start to rev up just over idle then bog down just below no matter how hard I press the accelerator, then after a second or two of acting like that it will then rev up to whatever point I have the accelerator pressed down to.

I am at a loss since it has done this for a long time never that consistent and I can never make it do it when I want it to. I thought maybe the fuel pump was going out but since it has done this for so long I figured it would have finally gone out by now. I replaced the IAC not long ago in an effort to tune the Jeep up some and it still bogs down just the same. Maybe its the TPS?

Test.

Put a fuel pressure gauge on the schrader valve on the fuel rail. Watch the fuel pressure from startup to bog. Should maintain a 49 psi pressure, plus or minus 5 psi.

Throttle position sensor is easily tested, but my money is more on fuel pressure as it only happens with a cold engine.

Does this happen with a warm engine or only on a cold start?

I'm betting on fuel pressure / leaky injector(s) too. Get a fuel pressure guage and take some readings, I bet you find your problem there.

If you need info on how to do it / what you want to read, I can help. PM me.

Since I am unable to provoke the problem to happen whenever I want I am not sure if it is only happening when the engine would be considered as starting in a cold condition only that it seems to only do it after it has sat a while whether it be only for 45 mins or over night. It has been pretty hot here lately in south GA so if I had been driving not long before it sat for a little while it would take some time for the block to cool down since the Jeep is dark green and sits in direct sunlight just about everywhere I park it. I guess I will try and see if the fuel pressure is right but how do I go about checking it? I see I hook it up to that valve on the fuel rail but where do I get the gauge to check it and how much will it cost me?

Some big box parts stores rent tools like fuel pressure gauges. Call around. Hooking it up couldn't be simpler. Find the correct adapter, hook that up to the end of the gauge and install on the schrader valve on the fuel rail.