airspeed

One of the better kits I have seen online is the Novak Conversion. I have never seen any of the parts or an actual kit but they seem to hve some nice technical write ups. Seems like they know what they are talking about. Basic conversion kits start at $6700 and go up depending on options. http://www.novak-adapt.com/catalog/engi ... /mmxj1.htm

In my manual they show a special TEE fitting with a pressure gauge that goes between the throttle body and the input fuel line. I think the pressure should be ~14psi.

By far the best upgrade I have ever done to my MJ!! I followed the MADXJ post, the brake lines were the challenge, use some stiff copper wire to figure out the bends and the lengths. I was doing more of a restoration so I went for new parts, 96 booster and master cylinder for ~ $142.00. If you go to the junk yard be sure to get the firewall spacer. To get my 88 brake light switch to operate I had to open the push rod hole up to .637".

The end play in the shaft won't be a problem. The spring loaded throttle plate will always keep keep a load on the shaft. I would go the the pull-n-save and pick up another, between the two you can make one that works.

The first wire is for the under hood light option. The second and third wires look like they should power the shift light. Will they plug together?

If your cooling system and thermostat are working properly, under normal conditions, no. If you were in extreme conditions -40, maybe.

I just changed the head on my 2.5 about 6k miles ago, no problems so far. I guess I broke all the rules, felpro gasket no sealant, reused the head bolts, same torque at all locations. I did notice that there was a "This side up" on the head gasket.

http://www.cliffordperformance.net/ Be prepared for some custom exhaust work for this header to fit a 2.5 Comanche.

Clifford does make a header for the 2.5L. I had one installed on my engine before I put it back in the truck, I just didn't like the way it fit. The stock cast iron header extends about 12" below the intake manifold and mates to the down-pipe. The down-pipe goes down and crosses over behind the oil pan and is supported in a bracket. The clifford header extends to the bottom of the oil pan and then bends straight back toward the transfer case. It would take some custom exhaust work to get it to mate to the cat on the other side of the car. I think the price of the Clifford was about $300!! I put a new stock manifold on my 2.5 and 10k miles later it has a crack, you can here the tick-tick-tick when I first start it up. If Clifford could make their header mate to the down-pipe on a Comanche I would buy it!

When looking at the photos I see a hex on the end of that plunger, can it be threaded out to bump the idle up a bit?

Here is the electrical schematic for the (ISACM) Idle Speed Activator Control Motor.

Now I'm getting confused, I'm looking in my 87 Cherokee FSM under 2.5 TBI. Under "throttle body" removal they say disconnet the wire harness from the ISC motor. That illustration matches what I have under my hood. A few pages in they start talking about the ISA motor removal and installation. What is the differance between ISC and ISA?

ISA or ISC (idle speed control) in my manual. I would go to the Pull-n-Save and find one on a 2.5 MJ/XJ. You can disassemble it and clean it up. There are a couple brushes and springs that fall out and (3) different gears, at first it looks complicated but if you study the assembly it will only go back together one way. The key is to study and note the disassembly process. What a difference that made in the cold start cycle for my 2.5!!

If you try to drill and extract the bolt threads "DO NOT" drill too deep. If you break into the water jacket you will have a water leak. I went through that exercise with a remanufactured engine and ended up have to return the head for a new one. I could not seal that threaded stud for anything Loctite, Silicone, J-B Weld, it woudl leak "a lot".

I took my ISC motor assembly apart for cleaning and have one spring, short heavy ~3/8" OD, not sure where it goes? It looks like it belongs in the hex pocket where the actual throttle punger goes, not sure. One gear is threaded on the plunger assembly with a small return spring, This must be an open loop motor that drives the punger out past the end of the threads to set the fast idle. Does the 3/8" pring stall the motor in a defined position or does it push the plunger back when motor power is off? How much grease/ lubrication if any required for re-assembly?

The 96 booster will require a .250"/.260" spacer to stand the booster out from the firewall. I used phenolic to help dampen noise, aluminum will work as well. The angle of the 96 booster brings the new push rod to the ideal position for the stock 88 pedal on my Comanche. I had to open the diameter of the hole on the push rod to ~.634" for my brake light switch to work. Fab up a couple of brake lines and you are ready to go.

I installed a dual diaphram booster on my 88 Comanche from a 96 cherokee, what a difference that made. That was the most effective upgrade I have ever done on that vehicle. Even at 75mph you can jump on those brakes and it will stop in short order, the stock rear proportioning valve works well too! There are some real nice writeups on this upgrade, try to run a search. Here is a good writeup, http://www.madxj.com/default.htm.

Here is what I had to do to make my horn work. This is only the lower ground jumper, there is another one up higher on the column, I couldn't get a good photo of it.

Here is the schematic of the horm circuit. The horn switch grounds to the rotating portion of the steering column.

Are you sure your horn worked before this rework. I had a similar problem with my horn and found that I had no ground continuity up the rotating column. The entire rotating part of the steering column was isolated, no ground. I used small ground jumper wires over the column U-Joints and now my horn works! I think I found this fix on the forum somewhere. I have a picture of my rework I can post later tonight.

I agree O2 sensor

The XJ's have a different valve cover and grommets. Look around for the 2.5 and see if you can find one of those big rubber grommets with the hard tube assembly attached to it. The trick will be removing it from the valve cover without breaking it. That rubber gets old and brittle.

Yes that is the fitting I was talking about. What is that tye-wrap on there for, that must mount different than mine. The one on my valve cover has a double lip molded into the rubber that snapes down in the valve cover. If I put a tye-wrap on mine it would make it looser. Mine was blowing oil out of that fitting all over the top of the cover!

My 88 2.5 cranks 4-5 times before it will start. In the cold it will idle slow for about 5 seconds then ramp up to a fast idle. The engine seems to be fairly smooth and driveable, even when cold.

The CCV (crankcase ventilation) are the two tubes on your valve cover. The large tube supplies air to the crankcase the small tube draws air out of the crankcase. There is no PCV valve on the 2.5 TBI, I believe the early version carb. 2.5 had a PCV. I have not been able to find the larger CCV right angle grommet that comes out of the valve cover. I glued mine back in with Ultra Black RTV, if you are real careful and don't move it around it will hold. Caution I broke the rubber flange off mine trying to take it out, I found a good used one at the pull-n-save. A good test for blow by is with the engine warm and idling, loosen the oil filler cap, there should be pulsing vacuum pressure holding the cap to the valve cover. It should kind of sit there and bounce.