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99 XJ 4.0 Engine Missfire Won't Start

D_Stevens

NAXJA Forum User
Location
Kentucky
Brand new here!

Earlier this week, my XJ began to strain a bit when starting, and after starting it a second time about 30 min later, the check engine light came on. The light was not flashing, so I took it to advance auto the next day. The codes read for a miss-fire in cylinders 3 & 4. I purchased new spark plugs thinking that was the issue. Due to a major snow storm and a lack of a garage, I was forced to limp along to work for a couple of days before I could even get under the hood. This morning when I attempted to start it, the engine would turn over but not start. I borrowed a neighbors car to get to work, and replaced the spark plugs this evening.

Now I am still facing the same problem. The engine will turn over and only "start" when I give it gas (bad I know). As soon as I let off the gas, the engine dies. It is also burning oil.

Both of the old spark plugs have a coating of oil on them.

What do you guys think? Worn piston rings? Worn valve guides? Blown head gasket? Worn out distributor cap?

Any ideas would be great!
 
UPDATE: It lives!!! Kinda. I replaced the distributor cap, but to no avail. I then replaced the wiring and the rest of the spark plugs. I finally got it to start. However, it is still running a bit rough. I am skeptical of my connections on cylinders 1 & 6. I just didn't get that "click" I wanted when I was connecting them. I am now going to wait for warmer temps to retry on the wiring.

FYI: Working on an engine in 12 degree temps in a foot of snow sucks.
 
How many miles on this engine?

Looks like you have done the usual tuneup stuff of spark plugs, spark plug wires, distributor cap and don't forget to install a new rotor too. And yes, be sure that the spark plug wires "click" onto the spark plug.

I'd then drive it for a while and see if any check engine light pops.

As for oil burning, how much does it burn to a specific amount of miles? Performing a simple compression test is never a bad idea for a snapshot in time of the internals of your engine. The spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

Also verify that your CCV system is working properly. Not unusual to have to replace the hoses and grommets on this as you get into the higher mileage bracket. Check inside your air filter box to see if there is any oil in there....
 
.....still facing the same problem. The engine will turn over and only "start" when I give it gas. As soon as I let off the gas, the engine dies.


For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging.

Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem. A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics.

The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will usually relearn the idle settings after a short period of driving and the engine will start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. Handheld testers are very inaccurate and will usually pass marginal alternators. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance for smooth starts.
 
So I am now leaning toward a cracked head gasket.

I have replaced all the wiring, plugs, distributor cap and rotor, and I went ahead and replaced the ignition coil.

The engine still has a consistent misfire and the check engine light came back on. The codes once again read for a misfire in cylinders 3 & 4.

I went ahead and pulled out the new spark plugs from 3 & 4 and they looked like this:
NzdRO2I


So how screwed am I?

I am devastated, this is my only vehicle.
 
Brand new here!

Earlier this week, my XJ began to strain a bit when starting, and after starting it a second time about 30 min later, the check engine light came on. The light was not flashing, so I took it to advance auto the next day. The codes read for a miss-fire in cylinders 3 & 4. I purchased new spark plugs thinking that was the issue. Due to a major snow storm and a lack of a garage, I was forced to limp along to work for a couple of days before I could even get under the hood. This morning when I attempted to start it, the engine would turn over but not start. I borrowed a neighbors car to get to work, and replaced the spark plugs this evening.

Now I am still facing the same problem. The engine will turn over and only "start" when I give it gas (bad I know). As soon as I let off the gas, the engine dies. It is also burning oil.

Both of the old spark plugs have a coating of oil on them.

What do you guys think? Worn piston rings? Worn valve guides? Blown head gasket? Worn out distributor cap?

Any ideas would be great!

Looks like a few issues here. However you didn't mention when you replaced the spark plugs in cylinder 3/4 of the time duration it took to re-foul the new spark plugs in cylinder 3/4.

Blown head gasket will give you the following criteria depending on the severity of the gasket damage.

1)Do you see bubbles in your radiator (radiator cap off)? It can be small bubbles or steady strong bubbles, if so then head gasket is blown.

2)Do you see coolant leaking outside of the engine block below the spark plugs and the lower engine block?

3)Do you see oil leaking below the spark plugs and lower engine block?

4)Are you losing engine coolant?

5)Is check engine light still on, and no codes reading on failed IAC motor? (If you are pressing the gas pedal lightly to get the Jeep to continue running, this usually indicates a failed IAC)

Now the pictures you showed with the fouled spark plugs indicates that you have oil creeping into the combustion chamber. The pictures shows wet oil, but I can't really tell if it is also coated with engine coolant. If it is oil, it is either getting past your piston rings or leaking downward from the valves. Depending on which it is, a mild upper engine work would fix it or a complete rebuild.

I am not sure of the 1999 models fall under this criteria: Link below mentions cracked head between cylinder 3/4?

http://www.cherokeeforum.com/f2/00-01-xj-cracked-cylinder-head-overview-118922/

I will try to help as much as I can!
 
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