Eagle

I wish I had thought of the 2.5L overflow bottle when I did my expansion tank upgrade. Live and learn.

You don't have a choke -- they don't exist with electronic fuel injection. So we've eliminated one possibility, and now you know what mechanic NOT to go back to. It might be dirty injectors, or it might be the CPS showing the first signs of old age. Also possibly even the oxygen sensor. If it's old it may not be responding fast enough to changes in the exhaust flow. Typically, though, with the O2 sensor failing you get backfires when you let off the throttle. How old is the CPS?

Possibly a bent valve, or a collapsed lifter?

Those springs look as good as new. Last year I took leaves and parts from four different springs, all of which had broken leaves, and mixed and matched to put together two complete springs. I'm in the rust belt, so I had a lot more work than you're facing. Center pins could not be salvaged. One I had to cut off. The other I was able to get the nut off after using a nut buster on the nut, but the shank was bent. I used socket-head cap screws from Lowe's, but (as others have pointed out) the heads are too large and need to be ground down slightly. In the process, I discovered that there are two different types to those rebound clips (the straps riveted to the third leaf). There are short ones, that leave the cross pin sleeve basically in contact with the main leaf, and there are "tall" ones that leave enough gap for an additional leaf. I have no idea why the difference. It might be for different rate springs, or it might be a difference in the year of manufacture. The leaves I was working with had so much rust flaking that I had to work on them with a ball pein hammer and a cold chisel to knock the flakes off. Then I swabbed them with rust killer. Once that dried, I gave them three coats of black Rustoleum, and put them back together. The unloaded arch seems to be the same for both springs but, because of the mix-n-match origin, I don't know if they are the same spring rate. I hope so -- although I also hope I never have to use them.

Interesting. I went through two with my wife's XJ, as well. But I bought the first from the dealer, and it lasted exactly one year. I bought the second from Auto Zone because it has a lifetime warranty. So far, so good. If the code you're getting is injector specific, it seems like you've replaced everything except that part that's probably causing the problem. Why not try another injector?

Same thing happened with my wife's 2000 XJ a few years ago. What code did you get -- by number? Injectors don't "fire," they inject, so I'm not sure from your description if you got an injector code or an ignition code. In my case, the code was for ignition. After replacing all the spark plugs (since the vehicle had 90,000+ miles on the original plugs at the time, the cure finally turned out to be a new coil rail.

You're off to a good start. Good find on the pads -- I wish I had known about them when I was refurbishing a set of springs. The rebound clamps are riveted to the third leaf, not the main leaf. To replace, I used 1/4" bolts and the smallest steel tubing I could find that would fit over the bolts -- don't remember if it was 3/8" or 7/16", but my best guess is 3/8".

Honestly, I thought "MTF" must be some new brand of lubricant that I hadn't heard of.

my best guess is Manual Transmission Fluid. or My T.A.R.D.I.S. Flooded... The pool in the library might have been a bad idea after all... Probably a good guess. 71 years on the planet, and this is the first time I've ever encountered gear oil being called "fluid." WE'RE HERE TO COMMUNICATE! WHY CAN'T WE JUST USE WORDS?

MTF? Mambo Tango Foxtrot? WTF does MTF mean?

That's not unexpected. The question is, under what conditions does it start clattering and the light flickering? How many miles on the engine, what type and weight of oil are you running, and what brand of oil filter are you using?

No, the bottom left is not an idiot light. It's a blank space. That's where the fuel gauge goes for the clusters that have a tachometer.

Unless the existing engine is blown, rather than just worn out, I would rebuild it, doing as much of the work myself as possible. [Hint: It ain't rocket science. Even I can put an engine together and have it run.]

Yes, it's a budget way to do a slip yoke eliminator. Rather than buy a complete rear housing and output shaft, the stock (late model) tailshaft is cut off ("hacked") and then tapped to accept a bolt that holds the yoke in place. This also requires a custom driveshaft with a slip joint in the center. You will need to find out if your output shaft has already been cut off, or if it's still full-length. If it has been cut off, you can't run a slip yoke on it because there probably isn't going to be enough travel.

What idiot light?

Yes. I use a lot of Crown parts. They specialize in Jeep stuff (along with Hudson!). So much so that their Jeep parts use Jeep part numbers. Ratio for the XJ/MJ manual box was either 20:1 or 24:1. VERY slow ratio, and I can't imagine actually wanting to replace one with another of the same. That said, it's a basic Saginaw box, and the same box was used in AMC cars for decades. Go junkyard, or splurge on a rebuilt.

First step is to determine if the water causing the rust attacked from the underside or the inside (hidden leak).

Something wrong? Yes ... you're buying Rusty's junk. I made the mistake of buying a Rusty's adjustable track bar. I've had the old factory track bars, the ones with no grease fitting on the frame end TRE, last over 100,000 miles. The Rusty's adjustable lasted less than 10,000. Fortunately, on an adjustable the TRE is replaceable. One of my friends in NAXJA NAC, however, had the threaded insert at the upper end of the bar rip out of the tube. You can't fix that with a new TRE from NAPA. I really don't understand how Rusty's stays in business -- or how he sleeps at night.

Correct -- assuming it's all original. No. There are no aftermarket 15x8 wheels that have as much backspacing as factory Jeep wheels. Unless you get a set of factory Jeep 15x8s, the wheels will take care of any spacing issues. What you will have to look out for is the shoulder of the front tire hitting the lower back corner of the wheel arch when turning. Acceleration will be worse, and 5th gear will be nearly useless. I ran my '88 on 31s for several years with 3.73 gears. In terms of speed-to-RPMs, this combination is exactly equal to stock tires with an automatic and 3.55 gears. Very nice for street, but 4.10s would have been better for off-road. I am currently running 31s on my '88 XJ with the stock 3.07 gears. I've been driving manual transmissions for well over 50 years so I'm not likely to burn out the clutch, but fifth gear is only useful on highways with a speed limit of 65 or higher. With 3.55s, you'll be somewhere in between my two examples. A new speedometer gear. What don't you understand? Find the chart for the tire size. Find the pair of columns with your gear ratio, and each row tells you the RPMs your engine will turn in 4th and 5th gear for the road speeds listed on the left. For your situation, 31" tires and 3.55 gears, at 65 MPH the engine would turn 1956 RPM in 5th gear, and 2608 RPM in 4th gear. That's not a horrible setup.In fact, a stock 4.0L 5-speed on 225/75-15 tires would be turning 1821 RPM in fifth gear and 2428 in fourth gear at 65 MPH, so your proposed setup is actually a slight improvement over a stock five-speed. Yes

Doesn't have to be '87 - '90. The older ones ('84 - '86) will also work if you change the speedometer cable. With the older ones, you MUST get one from a vehicle with the same number of cylinders. The older ones had no calibration potentiometer. The newer style have a potentiometer that allows calibrating for 4-cylinder or 6-cylinder.

What year, and do you have a functioning axle disconnect?

Why not?

There's nothing really wrong with that. It allows the use of the stock shocks.

Not great. Rosin-core solder is used for electronics soldering and not generally used for other types of work. If it doesn't say "Rosin-Core" on the label, it isn't rosin-core. Radio Shack is still the source for electronics soldering supplies IMHO (until they fold completely, which could be any day now).

I'll add another vote for air bag spring helpers. Not a factory option. As has been said, photos would help.