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Unread 03-01-2011, 06:33 PM   #1
provinT13
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2.5L cold miss

Recently my YJ has had a slight miss fire on start up. I'll come out in the morning to start it up, after about 30 seconds it goes away and is running fine. It's not sporadic or idling all over the place. A friend at work said it could be that the cylinder has no compression when it's dry, then when the oil gets there, the oil gives it compression, which means there could be a dead cylinder soon. I am not getting any codes and have not done a compression test or looked at the plugs, 170,000 miles, plugs, cap, wires, rotor all changed about a year and a half ago. Anyone else have any ideas on what it could be?

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Unread 03-01-2011, 07:36 PM   #2
moonshinefuel
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Seems to be, that is a worst case scenerio. I am doubting seriously its anything to do with the rings. This could be fuel, a sensor, a lot of different things, and a year and a half of the last tune up can be a long time depending on how much you drive it. I just don't think its anything to do with the rings, or the soon to be dead cylinder theory. Unless this engine has been severly abused or neglected or something, I just don't see that.
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Unread 03-02-2011, 09:56 AM   #3
Que89YJ
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Clean up the throttlebody and do a cursury check of the ignition system and the distributor. There was someone else here describing the exact same symptom with a sloppy timing chain. Do you hear any noise coming from the chain cover area?
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Unread 03-02-2011, 04:32 PM   #4
moonshinefuel
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Quote:
Originally Posted by Que89YJ View Post
Clean up the throttlebody and do a cursury check of the ignition system and the distributor. There was someone else here describing the exact same symptom with a sloppy timing chain. Do you hear any noise coming from the chain cover area?
Good point, if that's the original timing chain at 170,000 miles, it's way overdue for a change out. Mine was worn pretty badly at 145,000 miles. The 2.5 engines are a single chain with a tensioner. The 4.0 timing chains are doubled and tend to last longer.
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Unread 03-02-2011, 06:23 PM   #5
provinT13
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To my knowledge the timing chain hasn't been replaced. The only whine I hear seems to be coming from the power steering pump. I'll check my ignition system now and take a closer listen at the timing, will report back soon
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Unread 03-02-2011, 07:01 PM   #6
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Distributor cap and rotor are still in perfect shape. Throttle body looks fine, I haven't pulled the plugs yet but don't really see a need to since the misfire goes away, if it were a bad plug it would be constant correct?

This is what I am hearing. The ticking at the end has been going on for a bit now too, are those the lifters?

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Unread 03-03-2011, 08:28 AM   #7
Que89YJ
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It sounds too deep for the lifters. You can check your timing chain by pulling your distributor cap and by using a socket on the crank pully. Twist it one direction until you see the dizzy move and then the other direction and see how much you need to move it. Thats how much chain slop you have.
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Unread 03-03-2011, 09:13 AM   #8
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To be honest, if the miss goes away after running for 30 seconds, I would put about that much time into trying to figure it out! As long as it goes away and it runs fine otherwise, you are golden! These engines are rather primative by today's standards, but were designed when electronic engine controls were still at the bottom of the engineer's learning curve on engine management, so any sensor that is slightly out of spec can cause rough running at times.
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Unread 03-03-2011, 09:25 AM   #9
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http://www.jeepforum.com/forum/f12/1...93/index2.html
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Unread 03-03-2011, 01:11 PM   #10
moonshinefuel
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Timing chain slap does not go away, when my timing chain was going south, I could hear it most at a very low idle, a random tapping, the slapping of the chain against the inside cover assembly. A good timing chain and tensioner will help the engine run better as well, a loose, slapping around chain will do no favors as to how an engine runs.
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Unread 03-03-2011, 01:28 PM   #11
provinT13
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I'm not hearing any slapping or tapping, just the misfire for a bit then it's gone. I don't want to let it sit and turn into something worse, but I am still at a loss. I don't have much experience working on engines so I am still not sure what it is.


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I don't seem to be experiencing any of the problems the PO of that thread has pointed out. Mine has a slight miss on cold start up, no knocks or ticks, the only tick is at the end when I shut it off which lasts for about 20 seconds. After the engine warms up for about 30 seconds it runs fine. The idle isn't bad when it is warming up, but I can hear a stutter, something is missing.
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Unread 03-03-2011, 01:41 PM   #12
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A water pump bearing can start to make noise when it is in its beginning stages of going bad. It is kind of difficult as it can be many different things. So this is where an engine starts to get old, mine is going on 314,000 miles soon original block. Your engine is young in my view. So high mileage maintenance becomes something to look at. I am on my 3rd timing chain assembly 1st was the original, 2nd was around 160,000 thousand miles, 3rd I changed out a little early around 240,000 miles or so, and now I am going on 314,000 miles almost. I also changed out my hydraulic lifters when around 200,000 miles. The push rods generally last forever, and the rocker arms usually last too, but I did replace my rocker arms. It could be a lifter, it is possible. But knowing for sure requires looking at that a little closer.
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Unread 03-03-2011, 01:57 PM   #13
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http://www.jeepforum.com/forum/f12/f...-ones-1140414/

I actually had the exact same problem, and still have it to a degree. Mine is coming from a lot of different factors and I'm eliminating them one-by-one.

The main one for me was leaking injectors. It has started doing it again since then, so I'm not sure if that was the main cause. Even if it's not the same as yours, hopefully that thread will give you some places to start looking!

I'm still suspecting my timing chain and possibly sticky lifters.

Any recent changes in driving habits? I suspect sticky lifters on mine because it started when my commute changed from an hour of highway driving to a couple miles that never let it warm up and I ended up going *way* too far between oil changes.

I'm interested in what your issue is, maybe it'll help take the last of my start-up stumbling out of mine as well.

Does the stumbling seem random or rhythmic, btw?
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Unread 03-03-2011, 08:22 PM   #14
provinT13
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Quote:
Originally Posted by CrawlingForward View Post
http://www.jeepforum.com/forum/f12/f...-ones-1140414/

I actually had the exact same problem, and still have it to a degree. Mine is coming from a lot of different factors and I'm eliminating them one-by-one.

The main one for me was leaking injectors. It has started doing it again since then, so I'm not sure if that was the main cause. Even if it's not the same as yours, hopefully that thread will give you some places to start looking!

I'm still suspecting my timing chain and possibly sticky lifters.

Any recent changes in driving habits? I suspect sticky lifters on mine because it started when my commute changed from an hour of highway driving to a couple miles that never let it warm up and I ended up going *way* too far between oil changes.

I'm interested in what your issue is, maybe it'll help take the last of my start-up stumbling out of mine as well.

Does the stumbling seem random or rhythmic, btw?
It seems a little random, but not all over the place or rough at all. No change in driving style, I drive maybe 2 miles per day for work, very close to home. I ALWAYS let the engine warm up, and change the oil every 3,000 or about every 4 months or so. My dad also suggested a leaking injector, if I pull them what should I look for?
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Unread 03-04-2011, 04:19 AM   #15
f0rd2001
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cold miss

I have the same issue and havnt found a solution. 93 yj 2.5l. I almost thought someone was talking about my jeep. I did complete tune up, didnt help. No codes. Cleaned tb didnt help either. Hope you figure it out, very interested in what you find. I have had my yj for 11 years and fought a similar issue years ago, replaced iac fixed it till now. That time it set a code and didnt run well till it warmed up.
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