State

I've done a ton of searches and so far I can't seem to find a decent answer.

I own a 98 XJ with an issue that has me scratching my head.
I recently replaced the engine with a standard 4.0L at first the timing was off, after repairing the timing it ran beautiful for about twenty miles at that point my engine overheated.
Now, my car has been in limp-mode. Here are the symptoms:

* rough idle
* stalls at stop lights (unless I keep tapping the gas to keep it out of the lower RPMs)
* pulling codes p0300, 0303, 0304

I have replaced since then:

* camshaft position sensor
* Plug wires
* Plugs

Do you have any idea what I could replace next?
I don't want to keep throwing money at it hoping something sticks.

Thanks guys

ZINGGG

You say it overheated... Did you do any maintenance to the cooling system after that point? When's the last time the radiator, water pump, thermostat, fan clutch, hoses and radiator cap were replaced?

State

I flushed the hell out of the radiator and replaced the hoses. I top off the radiator with h2o when I need to drive it, but at this point i try to keep the jeep parked as much as possible until I figure out whats wrong. The radiator is like a heroin addict, it is physically there, but lacks any motivation to do its job.

I've ordered a new radiator. I haven't touched the water pump, thermostat, or fan clutch.

tjwalker

1. First of all, how badly did it overheat? If these symptoms started IMMEDIATELY after the overheat, it's entirely possible you blew the head gasket between cylinders 3 and 4 during that overheat. Run a compression test on all cylinders and see how cylinders 3 and 4 match up with the others. If both of those cylinders are low, then a head gasket replacement is on your "to-do" list. The compression spec for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

2. If compression is okay, finish the tuneup with a new distributor cap and rotor. I didn't see those parts listed as new.

3. Verify fuel pressure. You should have 49 at idle; check it with a fuel pressure gauge which can be rented from many parts stores. Gotta use a gauge; no shortcuts.

4. Test your ignition coil for both primary and secondary resistances with a service manual and a meter.

5. Verifying vacuum with a vacuum gauge; they can tell you a LOT. On most engines, intake vacuum should be steady between 16 and 22 inches. A lower reading usually indicates a vacuum leak, but it might also indicate an exhaust backpressure problem (such as a plugged catalytic converter) , worn valve guides or weak valve springs. A vacuum reading that gradually drops while the engine is idling almost always points to an exhaust restriction. An oscillating vacuum reading usually indicates a leaky valve or worn valve guides.

6. Oh, and as mentioned.........gotta figure out root cause of your overheat or it will overheat again. As long as you're putting in a new radiator, that would be a good time for a new water pump and thermostat while you are at it. None of these parts are that expensive. There is no better money spent than that spent on your cooling system.

DFlintstone

I don't know your whole situation...I myself wouldn't be in any hurry to replace the radiator if I hadn't checked my thermostat. (or pump). I've seen t-stats, than when dropped in boiling water didn't open up, and djb had some great photos of pump impellers that had the blades just gone! Just a metal disk.

Dieing at idle, first thing..vacuum leaks, Then later maybe conciser cleaning the IAC.

One quick, easy test for a really shot head gasket is to power-brake it with the cap off. If it's bad it will bubble, or hammer a geyser of the bottom of the hood.

Did you gap those new plugs to .035? Just a little thing, even when they come right, somebody might have dropped the box.

Fancy term " dynamic compression", just means unplug a plug and note the rpm drop. Pulling it from the cap lessens the chance you will be holding a live wire. If I had a miss and wanted to find which cil, I'd probably start by getting zapped doing that.

I'd always listen to TJ, and am 2nd' ding 96 sport, good to know that cooling stuff is right......