98 XJ motor swap low power

[Makima_xj]

Hey all. Got a 98 xj sport auto I recently did a 98 tj sport swap with. Xj has 183k and tj motor is 103k

No cel

Idle is 720-740pm
Temps haven’t climbed more that 215 under hard load and generally sitting at 200-210

I’m having big issues on highway speed hills with very low power. On big hills in the mountains I’m foot to the floor at around 3k and barely holding 50mph. On the flats it’s working hard to get up to 65.
I’m also getting a good amount of heat coming af my feet from the firewall which is new. Previously I could do the same roads at 75 without pushing the engine much.

New parts: fuel pump, upstream o2, plugs wires cap and rotor, new high flow Cat, exhaust mani and water pump.

Also throughly cleaned my AFE cold air filter in case it was choking.

I also today swapped the throttle body to the one the TJ motor came with along with all the sensors with not much change.

Symptoms aside from struggling for power under load it seems to get sub 55mph performance it’s revving higher than it was before to achieve the same result.

Things maybe I should look at?: injectors, coil, cam and crankshaft sensors?
I’m at a loss.

Any help would be greatly appreciated since this is my daily.

 

[RCP Phx]

Have you tried adjusting the TCV cable?

 

[Anak]

Symptoms suggest a restricted exhaust.

How freely does the exhaust seem to be flowing out the tailpipe?

In taking apart the old stuff could you have dislodged enough rust to have plugged your muffler?

 

[Makima_xj]

Have you tried adjusting the TCV cable?

Yeah I have

 

[Makima_xj]

Symptoms suggest a restricted exhaust.

How freely does the exhaust seem to be flowing out the tailpipe?

In taking apart the old stuff could you have dislodged enough rust to have plugged your muffler?

That’s what I was thinking with the extra heat and lower too speed as a potential cause also. I looked at the Cat and it wasn’t great but I’ve seen a lot worse so I dismissed the muffler. I’m running a flow master super 10. Is it worth trying some kinda cleaner or just get a new one?

 

[Anak]

I can't imagine what kind of cleaner would work on a plugged exhaust system...

Is your system welded? Or are there clamps which will allow you to separate sections?

At the very least I would try removing your downstream O2 sensor and seeing if that opens things up. Yes, the computer will throw a code, but taking that O2 sensor out of the picture should not make much difference in how the motor runs. That will not tell you if there is a blockage before the O2 sensor, but it should help to clarify if there is a blockage downstream of the sensor (i.e muffler, though I would not expect a Flowmaster to plug up).

Another thing I would try is disconnecting the system at the header. Check to see if there is something wrong at that connection. Try hooking up a shopvac to the tailpipe (ideally with a shopvac that allows the hose to hook too the reverse side and blows) and see what kind of airflow you can get through the system.

 

[Makima_xj]

I can't imagine what kind of cleaner would work on a plugged exhaust system...

Is your system welded? Or are there clamps which will allow you to separate sections?

At the very least I would try removing your downstream O2 sensor and seeing if that opens things up. Yes, the computer will throw a code, but taking that O2 sensor out of the picture should not make much difference in how the motor runs. That will not tell you if there is a blockage before the O2 sensor, but it should help to clarify if there is a blockage downstream of the sensor (i.e muffler, though I would not expect a Flowmaster to plug up).

Another thing I would try is disconnecting the system at the header. Check to see if there is something wrong at that connection. Try hooking up a shopvac to the tailpipe (ideally with a shopvac that allows the hose to hook too the reverse side and blows) and see what kind of airflow you can get through the system.

Yeah I was looking at a cut away of the s10 and it looks like only some massive debris like a shop rag could clog it I ran the downstream o2 sensor removed and not much improvement if any. Could slowly failing injectors cause a significant loss of power without throwing a code? I’m going sto swap rails and injectors from the other motor to see if there’s any difference.

 

[Da XJ nut]

when was the last time you swapped the fuel filter? I only ask cause it's not on the part list you provided. could be starving for fuel

 

[RCP Phx]

when was the last time you swapped the fuel filter? I only ask cause it's not on the part list you provided. could be starving for fuel

The only filter comes on/with the pump which he already replaced! On top of that since it's a plastic tank they don't get rust only dirt from the fuel.

 

[Makima_xj]

The only filter comes on/with the pump which he already replaced! On top of that since it's a plastic tank they don't get rust only dirt from the fuel.

Correct!! Also checked fuel pressure last night and it’s at 51psi when revving rpm’s. I’m totally stumped.

 

[RCP Phx]

I would get a scanner on it that can log data in real time to look at what's going on!

 

[Tim_MN]

Rather than randomly swapping stuff, perform some diagnostic testing of the common and logical suspects. I would test the TPS, the CTS, and both O2 sensors. Testing the coil is simple.

As suggested already view the Live Data. Is the timing correct?

NTK O2 sensors and NOT Bosch or generic auto parts store brands?

Coolant in the exhaust, excessive oil, and/or excessive fuel will destroy a cat converter.

 

[Makima_xj]

Rather than randomly swapping stuff, perform some diagnostic testing of the common and logical suspects. I would test the TPS, the CTS, and both O2 sensors. Testing the coil is simple.

As suggested already view the Live Data. Is the timing correct?

NTK O2 sensors and NOT Bosch or generic auto parts store brands?

Coolant in the exhaust, excessive oil, and/or excessive fuel will destroy a cat converter.

Rather than randomly swapping stuff, perform some diagnostic testing of the common and logical suspects. I would test the TPS, the CTS, and both O2 sensors. Testing the coil is simple.

As suggested already view the Live Data. Is the timing correct?

NTK O2 sensors and NOT Bosch or generic auto parts store brands?

Coolant in the exhaust, excessive oil, and/or excessive fuel will destroy a cat converter.

Did a real time scan and no irregularities with sensors showed up. Checked timing two nights ago. What has popped up as of yesterday was the dreaded vibration from my TQ converter failing along with new shifting issues. Strange there have been no codes or anything. But I’m getting the shudder more and more and lots of heat under floor now.

 

[Makima_xj]

Rather than randomly swapping stuff, perform some diagnostic testing of the common and logical suspects. I would test the TPS, the CTS, and both O2 sensors. Testing the coil is simple.

As suggested already view the Live Data. Is the timing correct?

NTK O2 sensors and NOT Bosch or generic auto parts store brands?

Coolant in the exhaust, excessive oil, and/or excessive fuel will destroy a cat converter.

Reason I replaced and looked at the cat first was from all the oil in the pipe from the previously blown motor. Lots of burn off after the swap from the pipe.

 

[Da XJ nut]

my 97 has an inline fuel filter just off the tank. I assumed that the 98 was like mine....or is mine a unicorn?

 

[RCP Phx]

my 97 has an inline fuel filter just off the tank. I assumed that the 98 was like mine....or is mine a unicorn?

Someone just added it, it's not factory!

 

[ILLXJ]

my 97 has an inline fuel filter just off the tank. I assumed that the 98 was like mine....or is mine a unicorn?

My 97 had one too. Sure looked factory to me. I wonder if some got them because of left over parts.

JIM.

 

[garyst44]

Mine had too, its factory to me

 

[Makima_xj]

UPDATE:

Still dealing with the same low engine power under load (hills especially at highway speeds)

Got a Bluedriver scanner and ran through everything that was supported for an xj.

The only thing coming back abnormal to me is my short term fuel trim never changes at all during a drive cycle. Sometimes. When I start a new drive cycle it may say -3.1-3.1 and then next drive cycle say -.0-.0 but never will bounce around while driving.

I’ve replaced my MAP sensor, high flow CAT, crankshaft sensor, upstream o2, fuel pump, plugs, wires, distrib cap and rotor.

I have 31psi at idle and 50psi under load at the rail for fuel pressure.

My idle is about 730rpm and my idle TPS is 16.1.

My idle fuel trims are ST: (-3.1 never changing) and LT 4.7% (does move quite a bit while moving).

Anyone have any more ideas on what could be causing my issue? The engines seems like it holds onto rpm’s a long time before shifting and seems like when it doesn’t like to go very far above 3k unless in neutral.

I swapped fuel rail with injectors and had no change so I don’t think they are the issue. Is it possible even though I have a new upstream o2 that show voltage variations it could be giving false readings to the pcm? Or that the pcm isn’t utilizing those readings since the short term levels never change?

 

[Tim_MN]

Fuel pressure specification is 49 psi +/-5 psi. 31 psi is out of spec.

Did you install a genuine Jeep or NTK O2 sensor? Numerous threads on different 4x4 forums detail the driveability issues associated with Bosch and Auto Parts Store generic Chinesium O2 sensors.

IDK what the live data numbers should be, but the TPS and the O2 sensors can be directly can be tested. The symptoms suggest TPS malfunction and/or O2 sensor non-compatibility.