engine gremlin issue

[kirkandsylvia]

What would cause an engine to give the symptoms of running out of gas other than really running out of gas? Fuel pump and filter are new. Here is what it is doing. It starts with no issues, for the first few minutes, I can accelerate with no issues, but within a few minutes at cruising speed (60 mph) the engine starts sputtering like its running out of gas, with a full tank. If I floor the gas pedal, it will act pretty much fine. If I back out of the gas pedal to just cruise it, it goes back to sputtering. If I pull over and shut engine off and restart it right away, I can take off and cruise it for a few minutes again before it starts sputtering. Also, when it does the sputtering, the idle is rough. Once restarted, idle is fine until the sputtering comes back. Would the temp sending sensor or tps sensor give these symptoms if they are failing?
By the way, this is a 96 xj and its not giving any check engine light

[alittleoff]

I had a similar issue about 10 years ago. My '03 4.0L threw a misfire, cyl. 2 code. Like you, I checked the gas gauge although I knew I had close to a full tank. I eventually removed the #2 spark plug and discovered that the center electrode was broken and "floating" in the plug. So I think it was making contact with the ground. I replaced all 6 plugs with APP985's and all is good.

Steve

[6spdYJ]

See if it acts this way at one particular throttle position or range. The throttle position sensor is a variable resistor that tends to wear to minimal contact - particularly if it's been on the highway at one throttle position a lot. try running it slowly through the throttle range to see if there is one position it tends to stumble. If it does this, you likely have a dead spot in the sensor. Without throttle position feedback the cpu won't fire the injectors because it doesn't know how much fuel to give.

[kirkandsylvia]

I see what you're saying, but it runs fine for about 2 min at any speed, but then it starts stumbling like its sputtering for fuel. It appears that shutting it off and starting it back up again, it will run fine for again, a couple of mins before doing it again. OBD II scanner says no codes. I did notice when I drove back from town which is 14 miles to my house and primarily down hill all the way that it seemed to run fine indicating that light on the gas pedal kept it from sputtering. I would think a tps would be giving me issues from the moment I start it, not a few to several min later.

[Ol Man]

I would be suspicious of the new fuel pump.

[aw12345]

Lean misfire? full throttle over rides the fuel managment system/ makes it run in open loop if it runs fine under sustained full throttle/ full load down the highway the fuelpump is fine.

[kirkandsylvia]

So..if it runs fine under full throttle, what sensor is giving the ecm bad info that would cause this? I put a volt meter on the return signal wire from the tps to the ecm and I see with throttle closed the volts are at 1.2 and it will steadily increase evenly to somewhere around 6-7 volts. The input side of the tps has around 8 volts from ecm. Does this sound correct? And like I said before, no check engine light nor any codes on the OBDII when i scan it, which kind of leads me to believe that its not a sensor. I would think that a sensor going bad would send a code error...maybe?

[aw12345]

I would look for a cause of a lean misfire, o2 sensor look for varying voltage from it 0.0 to 0.8 volts, rapidly changing. First few minutes of running and full throttle are open loop with no O2 sensor input/ ecm feedback control

[kirkandsylvia]

I see 1.6 volts on one of the wires in the o2 sensor harness when ignition is on but hasn't ran yet

[kirkandsylvia]

I see the voltage on the black wire in the o2 sensor harness when ignition is on but hasn't ran yet at 5-6 volts..a green with orange stripe wire with 14.2 volts with ignition in run position. With engine running, black wire voltage steadily drops to 1.0 volts. Resistance on temp sensor is about 22.2 ohms when cold or hot, the other wire on temp sensor shows 5.1 volts with ignition on. Should the resistance change when engine warms up to running temp?

[kirkandsylvia]

And one more bit of a info... When it starts its sputtering, at idle it sounds like it is starting to starve for fuel and idle starts to drop, and then it will ramp back up in idle to sort of normal, and then start sputtering and idle starts dropping, and then ramp back up, almost leads to believe the ecm is trying to compensate by richening the fuel mix. You can also smell the exhaust is running rich when it does this

[aw12345]

Your coolant temp sensor should change resistance, it if feels like it runs way to rich find the coolant sensor return wire the connector should have 5 volts to it if it's a single wire connector ground it when it runs rough if that clears it go buy a coolant temp sensor

[kirkandsylvia]

The coolant sensor is a 2 wire connector. I just drove the jeep up to mail box..very light on the throttle, had no issues. When I got to mailbox (1 mile) I read voltage on black wire on o2 sensor and saw 1.5 volts. Drove it back..light on throttle, and saw 1.5v at home. Held throttle upoen to about 2500 rpm and watched voltage drop to 1.1 on black wire and then it started sputtering

[aw12345]

2 wire means one is 5 volts and sensor input the othes is a ground or most likely so measure with ohm meter with Key off If one is only a few ohms then that is the ground side ground the other one that shows 5 bolts and see if it starts running better.
O2 sensor has a 12 volt circuit that is the heater

[Lumpy Grits]

When was the last time you changed the fuel filter?
When was the last time you changed the spark plugs, SP wires along with the 'dizzy' cap and rotor(does this engine have a distributor?)
Check as many electrical plugs/connectors as you can, and the surrounding wiring for damage.
Check ALL of your GND(-)connections, to be sure they are clean and tight.
Since it's not throw'n a 'code'. Makes me think it's an intermittent connection issue.
Also-Look for vacuum leaks.....
LG