RENIX Brain

Thinking about freshening up my '89 (279K miles) with 4.0 and AW4. I'm talking about rebuilding engine/tranny. She runs OK but not like new, obviously. I want to go that route just to have a peace of mind for reliability.
The more I look into all the electronics, and especially the RENIX brain and all the affiliated sensors, the more I doubt if that is a good idea.
What are we all older XJ (87-91) owners facing with respect to availability/cost of RENIX-related spare parts? Say in 3 years, what parts would be impossible to get and one would end up diging in bone yards just hoping? I know that DC has already phased out some parts.
Help me make a good decision here. I don't want to spend $'s freshening up a rig that is considered obsolete and could get benched for a $10 hard to get part.
Thanks for any input ... Maz

Internally, the Renixnon-HO) engine is the same as the later engines. Intake ports on the heads got raised in '91, but the engine itself is the same. If you "freshen" the engine, it could be transferred into a newer XJ with some swapping of external parts, and either adapting the head or swapping heads.

However, the Renix computer is fairly reliable. The sensors are available from multiple sources. I don't think you need to worry that you'll be unable to service it in three years.

Over the past 3 years I have done SLEP (service life extension program) on my 88 XJ. I decided after 12+ years the sensors have served well.

I would replace one every couple of weeks then go for a while then replace some more. I started with the MAP and inlet air temp sensor. I then replaced the throttle position sensor and calibrated it using the multimeter method. I had it to the dealer and the tech told me my TPS was not set right.

I then replaced the knock sensor, coolant temp sensor, had the throttle body cleaned, ignition coil module, ignition coil, fuel injectors, fuel pressure regulator, a "new" distributor from the dealer to get a new sync sensor/ also known as the camshaft position sensor, and finally installed a "rebuilt" engine computer.

I had replaced the crankshaft position sensor with a high alt CPS before I started this systematic replacement program.

I found each item I changed the engine ran better. The only exception was the coolant temp sensor, don't remember any "improvement".

Over time sensors degrade, I decided to change them all before they failed.

I decided I was going to keep my XJ. I wanted to make it more reliable and replacing sensors was one way. I have also have all the suspension bushings changed, new motor mounts, new radiator, added an aux trans cooler, done maintenance on time, and more stuff than I can recall right now.

If you want to keep it then do it, you won't be disappointed. I am sure some sensors will get more expensive in time. I found some good on line sites for parts. I used either dealer or Standard brand components.

Thanks for feedback. What other on-line sources do you use besides Quadratec?
Also, I was thinking about buying a RENIX brain from a boneyard, just in case. What would be a reasonable price?
Martin, my hat's off to you for changing the coolant temp sensor (I assume you mean the one on the block). That sensor is pain to get to. I've wanted to take it out for flushing the engine block, but no dice. The engine block drain plug is next to impossible to take out, at least to me.
Thanks again ... Maz

Maz, the time to change the coolant temp sensor is when you are changing the water pump. It right there in front of you once the power steering pump is gone. I will admit I tried to remove the coolant temp sensor and rounded off the corners. When I had the dealer mechanic install the new distributor I also had him change the coolant temp sensor. He worked the full time they charged me for the job. He usually does work in about 1/2 the book time.

Also if you have not messed up the sensor you could cut the wires off it and place a 6 point socket on it and turn it out. This is the "can't go back" if it does not work because the sensor will be dead.

Take a look at www.rockauto.com for stuff. I got my computer from www.carparts.com since they did not worry about the core.

It sounds like you want to keep the XJ so do a SLEP, you won't be disappointed.