DangerXJ

Been fighting this motor for sometime. Consensus please. Jeep starts and runs decent up to temp and than will loose power momentarily than pick up if you throttle it hard it corrects itself again momentarily. It than wont idle correctly; sounds like its choking itself.
Once cooled down again it will run/drive decent until up to temp. Oil doesn't look creamy or milky but does look murky/runny.
Pulled plugs last night not one cleaner than other. Top radiator hose doesn't fully pressurize.
Truck will not blow a CEL.

Facts
New ignition coil pack
Just put new crank sensor in
New plugs 2 months ago
New h20 pump n thermostat recently
Head gasket done year and a half ago. 7k since job.

Thinking I've got a leak in the head again but puzzled how to truly diagnose. Any thoughts suggestions.

Thank you

tjwalker

1. Are you using any coolant? IE; having to add anti-freeze to the coolant reservoir? If you are and you have searched for an can't find any leaks, a cracked 0331 cylinder head is a possibility. Cylinder leakdown test and or a visual of the area around cylinder 3-4 with valve cover off and pressurized cooling system is a good idea. Did you have your cylinder head "tested" when you had the head gasket replaced to be sure there were no cracks in it then?

2. Test your coolant temperature sensor. Located on the thermostat housing. If this sensor is providing the computer with bad input, it can create problems with fuel/air mixture when engine heats up.

3. Test your fuel pressure when symptomatic to rule that in or out. Only takes a couple of minutes. For a 2000, you should have 49 psi, plus or minus 5 psi.

salad

If your coolant temp sensor checks out, consider replacing the O2 sensors. They're only good for about 100k or so. Once the ECU/PCM reads a warm enough temperature from the CTS, it uses all two (or four, if equipped) O2s to adjust fuel trim. Worn out, they can be innacurate without throwing a code.

DangerXJ

Is there a way to test the sensors ?

DangerXJ

The coolant temp sensor is new about 6 months ago.
I had the head machined when I did the head gasket.
How can u test fuel pressure I have never done that before

tjwalker

You can test the coolant temp sensor for resistance values with a meter and a manual outlining the specs. Oxygen sensors are not easy to test without the right equipment and know-how. Just because the coolant sensor is only 6 months old doesn't mean that it can't fail. I see it all the time, especially with aftermarket sensors.

If you don't have a manual, get one. That and a meter are absolute necessities for the do-it-yourselfer.

You had the head machined, but did you have it TESTED for leaks? (pressure tested, magnafluxed, etc.) There is a difference.