Jumped Timing?? - '95 XJ 4.0 - JeepForum.com
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  • 1 Post By cruiser54
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post #1 of 8 Old 09-15-2019, 07:24 PM Thread Starter
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Xj Jumped Timing?? - '95 XJ 4.0

My daughter has a 95 Cherokee Country that started having problems last month. On her way home from work in high temperatures outside, the Jeep (affectionately named Walter by her sister), sprung a radiator leak and went dead about 1 mile from home. It went dead - she cranked back up, but it was running rough and she made it. I replaced radiator, water hoses and thermostat. I tried to crank and it was idling rough - like not firing on all cylinders. I checked plugs and used a scope to check out cylinders. All were good. Spark plug gap was good and plugs were clean.

The only thing I found that could be an issue was a plug wire on cylinder 6, so I replaced all plug wires just to be sure (they were only a couple of months old). I cranked it up and it started running rough, backfiring a bit and smelled to be running a bit rich. Would not idle on its own. I don't have tools to check compression.

I would not eve rate as a shade tree mechanic, I'm just not afraid of basic repairs. Could it have jumped timing?

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post #2 of 8 Old 09-16-2019, 06:58 AM
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She probably cooked the motor to be honest.
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post #3 of 8 Old 09-16-2019, 07:19 AM
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keep cruiser comments in mind as we look at this, I am a hopeless optimist.
First I would not worry about it jumping time.

Ok the coolant is now full, the oil was checked and was not milkshake in appearance.
Engine starts - but idles poorly is the concern right now?
Did you disconnect the battery - (my guess) as a jeep has a relearn .
advise -
Before we tear into this - compression, coolant pressure testing, cap, rotor, eng sprayed coolant everywhere... lets let it relearn, google forum for tips.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 8 Old 09-16-2019, 08:11 AM
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Originally Posted by jtec View Post
First I would not worry about it jumping time.

……….. eng sprayed coolant everywhere...
I agree with jtec, start with the basics.

Buy a spray can of electrical contact cleaner. Disconnect and clean every engine sensor plug under the hood, and inside the distributor cap as well.

The Throttle Position Sensor hates water of any type, and can be damaged by excessive water intrusion. A faulty TPS or other sensor data distorted by water induced short circuits can cause the symptoms described.
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post #5 of 8 Old 09-16-2019, 09:02 AM
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If she drove it till it died after springing the coolant leak that greatly increases the chances the engine is toast, that means she probably seized the engine. You really need to do a compression check. The gauge is cheap and the test is easy. 20 dollars on Amazon for a gauge on Prime. Have it in a day or two. You can even rent them from nearly any autoparts store.

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post #6 of 8 Old 09-16-2019, 11:34 AM
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Is it sucking or losing coolant still? If so, then its probably warped the head. If not, I'd still do a radiator pressure test and compression test on the cylinders. Might also look at the cap and rotor. If moister got underneath there, it could have damaged some of the post.
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post #7 of 8 Old 10-06-2019, 09:23 PM Thread Starter
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Thanks for ll the suggestions. Unfortunately I have been swamped with too many other issues to even do anything since replacing radiator, cap and plug wire.

It fires up, just runs like crap. No visible coolant leaks anymore. Oil looks good. Old coolant did not look contaminated by oil.

This week I hope to have time to check engine codes like others suggested and then I am going to pull the valve cover off to take a look at things. I scoped the pistons with a small camera scope and did not see any damage.

Thanks for the help. I'll post what I find.
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post #8 of 8 Old 10-08-2019, 08:59 AM
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Perhaps one cyl is *not* firing. To check, start engine, let idle. Then pull the fuel injector connector off #1. Does the idle drop further? Put it back on. Did the idle pick up?

Repeat with #2-6, one at a time. If you come across one cyl where the idle does not change, you found your bad boy. If they all drop, your problem is not specific to a particular cyl.

As others have said pressure test, and compression test.
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