WTF is Renix?

[91mj97tj]

As to mileage, I made an 700 mile trip with 1K lbs of camping/tires/bumper in the bed and still managed 22 MPG on the highway.

not bad for a 20 year old truck with a "flawed" fuel injection system.

 

Point is, the Renix system is much more adaptable, runs the motor using realtime information from it's sensors, and is pretty much bulletproof.

It just takes a little love to make it reliable, but I honestly haven't worked on the engine management in a year. I've spent more time repairing hard drivetrain parts than anything in the electronics.

 

Just curious how many times did you fill your tank up on this trip?

[87manche]

As to mileage, I made an 700 mile trip with 1K lbs of camping/tires/bumper in the bed and still managed 22 MPG on the highway.

not bad for a 20 year old truck with a "flawed" fuel injection system.

 

Point is, the Renix system is much more adaptable, runs the motor using realtime information from it's sensors, and is pretty much bulletproof.

It just takes a little love to make it reliable, but I honestly haven't worked on the engine management in a year. I've spent more time repairing hard drivetrain parts than anything in the electronics.

 

Just curious how many times did you fill your tank up on this trip?

I used 29 gallons of fuel to drive from Salem MO, to Ashland OH

so a tank and a half. On the highway I average about 400 a tank. I fill it up when the low fuel light pops. It usually takes 18 gallons from that point, leaving me with a 5 gallon reserve in my tank.

[Eagle]

renix also DOES get better fuel mileage than the HO because the timing isn't so advanced (literally, advanced, not technologically)

Actually, it's getting better mileage because the timing is more advanced, not because it's less. Using the knock sensor allows the timing to be advanced to the optimum setting pretty much all the time, and when the engine gets loaded down and starts to knock the sensor backs it off enough to prevent damage to the pistons.

 

Even though I live in a coastal state (elevation at my house is about 450 feet above sea level), the last time I replaced the CPS in the '88 Cherokee I threw in a high-altitude CPS just to see what would happen. The vehicle is 19+ years old, 265,000+ miles, and in normal commuting (15 miles each way, of which maybe 5 is highway) routinely delivers 21 to 23 MPG. I haven't taken a long trip since putting in the high-altitude CPS but I think I'd probably be pushing at 25 MPG if I stayed near the speed limit.

 

Best mileage ever was a trip to Vermont when the Cherokee was about a year old -- 28 MPG. There's no way an HO will produce mileage like that. My wife's 2000 XJ typically runs at 16 MPG when she drives it, and 18 MPG when I drive it. If any of my Renix XJs or MJs turned in mileage like that I'd figure it was due for a rebuild.

[xipantera31ix]

would the renix motors benefit from using H.O. injectors? just curious cause they are just a junkyard away.

[Oizarod115]

would the renix motors benefit from using H.O. injectors? just curious cause they are just a junkyard away.

 

different lb/hr rates... IIRC the HO uses a 21# and the renix (i know) uses a 19# (ford 5-0 injectors are a direct swap for renix engines)

 

but just cause its from a 5-0 doesnt mean itll improve performance, it just particalizes (sp?) the fuel better due to a 4-hole spray rather than the 1-hole stock.

[xipantera31ix]

hmm shot in the dark then I guess

[Duner]

Ok, my tired 90 renix is only getting about 15mpg the best it did before the lift and 2wd was 17.7mpg so I don't think my loss was that bad but I'm curious about changing some things on the engine.

 

First has anyone just changed the cam and injectors on the renix motors, the way the computer controls the engine you should see good performance gains and how do you know if your knock sensor or O2 sensor is good or bad I have seen some forum answers where they say just replace every sensor on the renix - they're cheap - but I didn't want to fix something that seems to be working.

[JeepcoMJ]

duct tape

[Eagle]

First has anyone just changed the cam and injectors on the renix motors, the way the computer controls the engine you should see good performance gains and how do you know if your knock sensor or O2 sensor is good or bad I have seen some forum answers where they say just replace every sensor on the renix - they're cheap - but I didn't want to fix something that seems to be working.

Changing a few sensors HAS to be cheaper than doing a cam. You have to pull the head to do a cam in the 4.0L engine -- there's no other way to remove the lifters. You wouldn't pull the head and install a new cam without doing a valve job. And my experience has been that doing a valve job on a tired engine without doing a lower end rebuild results in higher compression, which then starts pushing oil past the tired old piston rings. In short -- I recommend not doing a cam unless you rebuild the entire engine.

 

19-pound Ford 5-liter injectors seem to be a popular replacement for the Renix injectors. The flow rate is close enough, and the FoMoCo injectors have a better spray pattern so the improved atomization may improve mileage slightly.

 

The O2 sensor is intended to be replaced approximately every 75,000 to 80,000 miles. The original in my '88 XJ went a lot longer than that (actually, the ORIGINAL original failed a lot sooner but was replaced under a recall program, the corrected part lasted a lot longer than 80,000), the next one lasted less. If you don't know how long yours has been in place, it should be replaced because when it fails the mix gets too rich and the unburned fuel then destroys the catalytic converter.

 

In your situation, I'd suggest O2 first, if that doesn't improve mileage check the cat for blockage, and if that's good then think about the Mustang injectors. Also check your EGR valve.