• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

XJ 4.0 Sensor brands to stick with?

96Sportxj

NAXJA Forum User
Location
NorCal
Recently replaced the CPS with I dont remember what. And the o2 sensors with Densos. Next I am going to replace the MAP and air temp sensor all in the hunt of my missing mpgs... Anyway what brands are you guys having or not having luck with? I really want to go with the 20$ sensors vs the 70$ sensors. :banghead:

Also any tips on where to find the best prices on sensors? So far amazon has been best I can find price wise.
 
My pecking order for parts in general

-Dealership (sometimes surprisingly inexpensive for OEM quality)
-High quality stuff online
-NAPA
-Advance, Autozone, O'Reilly's

Unless you need it yesterday, stay away from the parts stores. Last time I went to O'Reilly's looking for a part (Moog track bar) oh, yeah, sure, they've got it in stock... for like $110... I bought the exact same thing online for like $60-something. Which wasn't much more than their shitty, Chinese house-brand junk, and in fact, I think they jack up the prices on the good stuff to make their junk seem more appealing. As far as brands go-

-NTK/NGK for O2 sensors (from what I understand, they originally made them for the XJ's anyways.)
-Pick-up coil/cam sensor: Still available from the dealership for $70 or so.
-TPS: Same thing as the pick-up coil. $50 or so I think.
-Crank sensor: NAPA
-Battery: NAPA Premium Gold will change your life...
-Spark plugs: Champion. Never noticed a difference between copper-cores and single platinums in my stock 4.0. They're about the same price, but the platinum plugs should last longer.
-Blower switch: We'll see how long the NAPA switch holds up. I've gone through two in probably as many years...
-Currently running a Davis Screamin' Demon ignition coil with, I believe, red Taylor ThunderVolt wires. No complaints except some mice chewed up my first set of Taylor plug wires at one point. Even chewed up, they worked fine, they were just chewed up. :smsoap:

Edit: Oh yeah, best way to find cheap parts online is to just plug the manufacturer and their part number into www.google.com/shopping I find that Summit Racing works really great for finding that info.
 
Last edited:
Can we circle back to the origin of the sensor replacement which is your decrease in mpg? I assume you have a 1996 xj. Auto? More info would help.
- Are there any engine mods you have done?
- How are you measuring mpg?
- What were your mpg numbers before and what have they decreased to?
- In what amount of time have you noticed your decrease in mpg?
- Have you done any diagnostic testing on your current sensors?
- Why did you change your CPS?
- What are your live data numbers for your sensors on an obd2 scanner?
 
OEM isn't always super duper special stuff, it may be exactly the same as you get anyplace, it just costs more. I've compared some of the OEM stuff and the stuff I get from Rock Auto, looks exactly the same to me. Vendors make the stuff for Jeep, they don't make their own parts, they just package it as Jeep.

I've had good luck with Standard brand sensors. I haven't had one fail or be bad out of the box yet. I'm always a little leery of trusting any brand too much, you never can tell when they will decide to pinch a few pennies or their quality control goes down.

Swapping parts hoping to get lucky is IMO the worst way to find a problem. New, doesn't mean better it just means new. Replacement OEM parts aren't necessarily the same parts they built the vehicle with.

Mileage or idle issues, the first place I usually start is vacuum leaks. Could be something as simple as loose manifold bolts or a cracked header. Not all header cracks cause issues, some do, they can venturi (exhaust blowing across a crack can actual suck air through the crack), a little extra air into the exhaust can cause the O2 sensor want to compensate by adding fuel.

My 96 isn't right, it uses too much fuel. I noticed when I reboot the computer it runs well for awhile until the computer relearns. Obvious some sensor is providing faulty info. Time to hook up the code reader.
 
1996 xj. Auto sport 4x4 with tow package 160k miles was 14-17mpg

Thermostat stuck open back in Nov in the snow and I ran her for a week like that with the temp never getting over 100 degrees. (Got 90 miles for a full tank that week) After replacing with a new thermostat 195* mpg went up but still down significantly @ 10-12mpg

- Are there any engine mods you have done?
Full tune up all done in the last few months
- plugs, wires, rotor, cap,
- air/fuel filters, seafoam,
- Walker CAT, New turbo exhaust with 2.5" pipe The original CAT on her was completely deteriorated and everything was loose and tons of stuff came out when i took her off. Was really hoping replacing it would get me to the 18-20 range..
- new oil and filter
- new radiator cap
- new starter
- How are you measuring mpg?
miles divided by gallons
- What were your mpg numbers before and what have they decreased to?
Best before the thermostat incident was 14-17mpg normally 220ish till fuel light. Now 12-16 190miles till fuel light comes on.
- In what amount of time have you noticed your decrease in mpg?
since Nov
- Have you done any diagnostic testing on your current sensors?
Nope
- Why did you change your CPS?
Last one failed, at a busy intersection at 8am.. was a ton of fun..
- What are your live data numbers for your sensors on an obd2 scanner?
No idea, last 3 blue tooth scanners have not worked, but have a 4th more expensive"r" one coming in the mail.

Best mileage I have gotten so far was yesterday. 100 mile round trip 55-65 the entire way, filled up at same pump before and after drive and got 16.35 mpg.


Plan is to try changing the thermostat, IAT and MAP sensors/senders

Here is my full log:
http://www.naxja.org/forum/showthread.php?t=1136257
 
Last edited:
What are your ambient temps you where driving this 100mph trip and got 16ish mpg?

Outside temp was probably in the 55-60ish range. I have noticed that my temp gauge shows a hair lower on the temp then it did before the thermostat change. 250 vs 210. I can try putting a piece of cardboard in front of the radiator and see if it makes a difference.
 
Buddy with a code scanner is showing code: P0443 The fuel filter in the gas tank has been moved to the outside of the tank to make changing it a heck of alot easier. but that was done about 8 years ago. Also when i take off my gas cap there is never any pressure. Is that normal?
 
OEM isn't always super duper special stuff, it may be exactly the same as you get anyplace, it just costs more.



I will disagree with you entirely on this point.

I have an original Renix labeled CPS in my MJ, I just bought two NOS Siemens/Mopar CPS for $30 each. Production date of 2003.

I'm good for a lifetime.


They are out there if you look.

Siemens is Bendix is Renix.........this is an original part.

The fact that I'm still using an OEM original 30 year old part.........that says enough by itself.
Guys keep replacing aftermarket parts like socks round here.



Dig deep.
 
Buddy with a code scanner is showing code: P0443 The fuel filter in the gas tank has been moved to the outside of the tank to make changing it a heck of alot easier. but that was done about 8 years ago. Also when i take off my gas cap there is never any pressure. Is that normal?

Tangential Hijack:

Fuel filter in the gas tank?

I am aware of the strainer at the pump inlet, but besides that, what fuel filter should be in the tank?

I believe the driver's side frame rail, above the rear axle is the correct, OE, location. If there is another arrangement I would like to know some details about it.
 
Tangential Hijack:

Fuel filter in the gas tank?

I am aware of the strainer at the pump inlet, but besides that, what fuel filter should be in the tank?

I believe the driver's side frame rail, above the rear axle is the correct, OE, location. If there is another arrangement I would like to know some details about it.

That is what I meant. :)
 
Umm...

I think you want that strainer to be in the tank if your pump is in the tank. Or did you move the pump out of the tank too?

I still think a strainer at the pickup is advisable.

I suspect I am missing something in this picture.
 
Buddy with a code scanner is showing code: P0443 The fuel filter in the gas tank has been moved to the outside of the tank to make changing it a heck of a lot easier. but that was done about 8 years ago. Also when i take off my gas cap there is never any pressure. Is that normal?

That P0443 Code problem may be part of your problem. The gas tank may be venting directly to the atmosphere and or the engine, not holding pressure in the tank, may be venting to the engine vacuum all the time. That is a a vent hose from the gas tank, or Gas Tank cap, or purge valve stuck open problem. It is not related to the fuel pump filter location. If you had a fuel filter issue, it would be running lean, overheating and have great MPGs.

Low coolant temp, T-stat opening too soon, sticking wide open all the time if it is fail safe T-stat that failed, ... can lower MPGs big time.

The exhaust mods may have cost you MPGs, the O2 sensor location is TUNED for the OEM exhaust.

The Muffler may be partly clogged with parts from on the old damaged Cat converter.

And not sure what any of this has to do with what "XJ 4.0 Sensor brands to stick with"

I use only Murray brand T-Stats made in Israel these days.
 
Walker CAT replacement, also replaced the muffler with a turbo muffler and the pipe with 2.5". Even started the jeep after cutting off the CAT and muffler to blow out any junk that might be in the pipe still.
https://www.youtube.com/watch?v=VJfPKzqneag

Reason for the thread is I am replacing sensors trying to track down why my mpg's suck and @cummins90 wanted to know why.
 
Back
Top