Symptoms of a imporoperly installed timing chain?

[xjtrailrider]

I ask because my 94 with a 96 4.0 and new timing chain gets terrible fuel economy. Its bone stock getting 10mpg

I have tried everything, replaced everything. Here is the list of new parts;

NGK O2
Champion plugs
CTS
MAT
MAP
injectors
FPR
Bosch fuel pump(old one died)
Accel cap, wires, rotor
Catyletic converter

Things I have tried;

I borrowed a known good ECU from a friends 94 XJ that gets normal mileage-no change.
Cleaned all connections and grounds-no change.
Using the GPS to check mileage between fill ups(the odometer is correct though)-results were the same.
Checked for vacuum leaks-none
Cleaned the TB and intake(I cleaned the intake in a ultrasonic cleaner)-no change.
Checked the brakes and axles for any parasitic drag-nothing.

Lastly, and why I ask, would a timing chain cause poor fuel economy? I installed a new chain set before I dropped the motor in and while I was replacing all of the seals and gaskets. I guess its possible that I got it off a tooth but I have done a good many with no issues. I have tried everything else so now I'm doubting myself.

The Jeep runs better than the other three in my driveway.

I am about to give up on it.

 

[89s15jimmy]

put cylinder number 1 on top dead center compression and take off the timing cover and see if the marks line up.

 

[Tim_MN]

The first thing I would suspect if you are not getting decent gas mpg's is O2 sensor problems, and/or a cracked exhaust manifold. Test the O2's and inspect/test their wire plugs and wires. Most Cherokee 4.0 L have a cracked manifold.

 

[cal]

Symptoms of an improperly installed timing chain are consistent:

1) the engine does not run right or usually at all.

If it idles, and rev's up to 5K, the timing chain is installed right and you have a different problem.

 

[xjtrailrider]

The first thing I would suspect if you are not getting decent gas mpg's is O2 sensor problems, and/or a cracked exhaust manifold. Test the O2's and inspect/test their wire plugs and wires. Most Cherokee 4.0 L have a cracked manifold.

I didn't add it to the list but it has a new manifold and I just installed a NGK O2.

 

[xjtrailrider]

Symptoms of an improperly installed timing chain are consistent:

1) the engine does not run right or usually at all.

If it idles, and rev's up to 5K, the timing chain is installed right and you have a different problem.

From my 35 years of experience and training, I agree. This thing has me doubting everything.

 

[xjtrailrider]

put cylinder number 1 on top dead center compression and take off the timing cover and see if the marks line up.

Its a PITA to pull that cover but if I have to I will........

 

[Green Mesa XJ]

I don't think it's timing related. Just because of how well you say it runs. If low mpg is the only symptom Is it possible there is a fuel leak somewhere? Torqconverter not locking up ?

 

[Tim_MN]

I didn't add it to the list but it has a new manifold and I just installed a NGK O2.

And you checked that that is no leak ? You tested the O2 for proper function, and continuity tested the O2 wire harness from the sensor to the PCM ?

New does not automatically mean good.

 

[xjtrailrider]

And you checked that that is no leak ? You tested the O2 for proper function, and continuity tested the O2 wire harness from the sensor to the PCM ?

New does not automatically mean good.

No exhaust leaks, cold or hot, checked by the old fashioned method of back pressuring the exhaust.

I have visually inspected the wiring harness from the O2 up to the fuel injectors and checked the continuity. But I have not performed a continuity test past that.

 

[xjtrailrider]

I don't think it's timing related. Just because of how well you say it runs. If low mpg is the only symptom Is it possible there is a fuel leak somewhere? Torqconverter not locking up ?

No fuel leaks. It goes into lock up but at a higher mph than my other XJ's. The 90 locks up around 40mph but its also on 4.10 gears and 31" tires, so its a lower ratio. this one will not lock up until almost 50mph.

 

[XJ-ARNIE]

You've gotta quit throwing parts at it. Think base engine. Compression test, fuel pressure test, how do the plugs look? Did you do the little sheet of paper trick to test the pcv? From there, I'd move to leak down, and fuel injector flow testing. Do you have any way to look at live fuel trim data? Or h2os data?

You mentioned a vacuum test was preformed? What were the results? Steady? At what vac?

You will eventually find a bad part in the motor, or confirm with testing that the engine is sound, and focus on the trans.

 

[RWKHausSupply]

From my 35 years of experience and training, I agree. This thing has me doubting everything.

Incorrect, to a degree or 3, literally.

You could have a low quality or poorly made timing set that is actually a few degrees off one side or the other. My engine came with one that was over 3 deg out. And it still reved to 6xxxrpm. still drove ok, but way down on power, compared to the billet set I installed in its place, that was exactly dead on, as it should be.

 

[RWKHausSupply]

Do a compression test.

I recommend, start engine, let it warm up to operating temp.
Then remove ALL spark plugs. Then read each cyl. you will find about 4-5 complete revolutions is all it needs per cyl. Log the value of each cyl, and report back with readings.

 

[md21722]

There are two coolant temperature sensors, one for the gauge and one for the engine. Have you confirmed that both sensors are good and the engine is going into closed loop? Operating temperature should be around the middle of the gauge, 210F. Is the tailpipe sooty? What do the plugs look like?

 

[xjtrailrider]

There are two coolant temperature sensors, one for the gauge and one for the engine. Have you confirmed that both sensors are good and the engine is going into closed loop? Operating temperature should be around the middle of the gauge, 210F. Is the tailpipe sooty? What do the plugs look like?

Both are new and working properly. But the CTS was my first suspect in all of this.

I like RENIX so much better. For me its easier to diagnose than OBD1. I'm thinking there has to be a wiring issue or poor connection somewhere in the engine bay. I'm not the best at working through electrical issues though.