'95 YJ 4 Cyl 2.5L Rough Idle - Jeep Wrangler Forum
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Old 11-28-2010, 08:41 PM   #1
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'95 YJ 4 Cyl 2.5L Rough Idle

Spent about $850 on new exhaust manifold, R/R vacuum hoses, and sealing up a hole on my exhaust pipe. Also spent about $50 on a new IAC valve which I replaced myself. Cleaned out the throttle body and my Jeep still idles rough. Any suggestions would be appreciated.

My Haynes manual tells me to also check the PCValve but suggestions on other threads state that this is nonexistent on my model.

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Old 11-28-2010, 08:51 PM   #2
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you have a CCV rather than a PCV. there is a line that connects to the front of the head. It's pretty small if I recall. It is part of your ccv and can get plugged up. unscrew it and make sure it's all clear. Also, there is a small section of rubber hose that connects it- make sure it's not cracked and leaking. This did the trick for me one time. Report back.

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Old 11-29-2010, 12:39 AM   #3
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I'd check the plugs, cap and rotor, and plug wires if you haven't already.
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Old 11-29-2010, 05:32 AM   #4
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Try a new gas cap. If it doesn't seal you can have issues too.
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Old 11-29-2010, 10:44 PM   #5
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gentlemen (going off the usernames here, apologize if i offend), i appreciate the suggestions. i'll check my ccv valve this weekend. as for the plugs, wires, rotor, and cap, it's already been done. will try a new gas cap if the ccv doesn't work, but what did you mean by a seal problem too? seal on the gas cap?
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Old 12-05-2010, 06:04 PM   #6
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status update... (@jgwalt) cleaned out my ccv and still idling rough. thanks for the reply though. will update once i get it resolved. thinking about taking it back to a shop to get another diagnosis.
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Old 12-22-2010, 03:09 PM   #7
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Not to deter from your original question Josi1089, but how do you clean/replace your CCV?
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Old 12-23-2010, 01:25 AM   #8
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if you can wait till this weekend i can put up pics. i may be wrong but maybe the community can decide.
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Old 12-23-2010, 01:59 PM   #9
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You could have a bad or clogged injector, have you tried running some injector cleaner thru it.
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Old 12-23-2010, 02:24 PM   #10
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Is the engine light on by any chance?
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Old 12-24-2010, 09:34 AM   #11
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It could be a number of things really. Just go throught the list and elininate them 1 by 1 starting witht the cheapest or easiest fixes first I would suggest. But here they are in no particular order:

1. Check vacuum hoses for leaks.

2. Check intake manifold gasket surfaces for leaks.

3. Check EGR or CCV valve for leaks or plugs.

4. Check fuel pump pressure, and fuel filter.

5. Check for leaking head gasket (requires a cylinder compression check)

6. Worn timing chain.

7. Timing out of adjustment.

8. Burned or leaking valves.

9. Dirty or clogged injectors or carb.

10. Idle speed out of adjustment.

11. Camshaft lobes worn.

Check that and let us know if and what fixed it.
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Old 12-30-2010, 01:01 AM   #12
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yo preditur... sorry it took long to post this, but below is pic of my engine. like i said the community can judge on whether i got this right. according to jgwalt i do not have a ccv. but to answer your question i pulled off the hose from the brass valve (i think this is my pcv) and unscrewed it to clean it. hope this helps. for the community, if i am wrong please feel free to correct my ignorance.
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Old 12-30-2010, 01:12 AM   #13
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@ garyk, i haven't ran a legit cleaner through the injectors... just poured in the stp fuel injector solution during regular trips to the gas station.
@ 60 mg, no light.
@ jenkins, your suggestions are money. do you have a shop in socal (orange county) by chance??? and on which fixes would you allow a novice to diy? and which ones should i take to a shop?
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Old 12-30-2010, 07:01 AM   #14
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yo preditur... sorry it took long to post this, but below is pic of my engine. like i said the community can judge on whether i got this right. according to jgwalt i do not have a ccv. but to answer your question i pulled off the hose from the brass valve (i think this is my pcv) and unscrewed it to clean it. hope this helps. for the community, if i am wrong please feel free to correct my ignorance.
I pulled my valve cover and discovered both pickup tubes were plugged solid. Took them both apart, cleaned and reassembled.
Made a slight difference. Don't forget to install a new gasket.
When you remove your oil fill cap on top of your valve cover (engine running) do you get oil spitting out or excessive air pushing from the opening?
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Old 12-30-2010, 08:54 AM   #15
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My YJ was running rough, so I added some Lucas injector cleaner. I would drop to almost 500 RPMs. Once I ran that stuff through, I was back to normal.
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Old 12-30-2010, 09:06 AM   #16
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My YJ was running rough, so I added some Lucas injector cleaner. I would drop to almost 500 RPMs. Once I ran that stuff through, I was back to normal.
+1
Lucas is good stuff.
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Old 12-30-2010, 12:11 PM   #17
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yo preditur... sorry it took long to post this, but below is pic of my engine. like i said the community can judge on whether i got this right. according to jgwalt i do not have a ccv. but to answer your question i pulled off the hose from the brass valve (i think this is my pcv) and unscrewed it to clean it. hope this helps. for the community, if i am wrong please feel free to correct my ignorance.
That is a picture of a CCV. The rear line goes to air cleaner and front line goes to special orifice at manifold. Make sure the orifice at the manifold is clean.
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Old 12-31-2010, 02:16 PM   #18
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@ garyk, i haven't ran a legit cleaner through the injectors... just poured in the stp fuel injector solution during regular trips to the gas station.
@ 60 mg, no light.
@ jenkins, your suggestions are money. do you have a shop in socal (orange county) by chance??? and on which fixes would you allow a novice to diy? and which ones should i take to a shop?
No I'm afraid I'm on the other side of the country in SC.

However half the fun of owning a Jeep is doing the work yourself, learning and sharing your experiences. That being said I recommend anyone willing to get their hands dirty and DIY. You should be able to go to your parts store and buy a manual such as Chilton or Haynes and it can help walk you through everything I listed.

But if its a daily driver and time is an issue then I suggest trying these first: 1,3, and 10. They are all quick and cheap to check and fix. Also you might want to replace the oxygen sensor. If its old and not giving good readings to your computer then your air/fuel mixture could be off.

If that doesn't work move on to: 2,4,7,and 9. These either take a little more cash, or time to do, but you shouldn't have much trouble with it.

If none of that works and your still worried about how your Jeep is running then you can dive deeper in the rabbit hole, or take it to a shop.
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Old 12-31-2010, 02:35 PM   #19
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did it start doing this "all of a sudden?"

a lot of times its moisture or a little bit of water in the fuel system. Did you run a full tank through it since the fuel injector cleaner? To rule this out, with a full tank of gas it should not idle rough. If it still does after a fill up, then its not water in the gas.

Three things an engine needs to run smooth. Gas, air and spark. One of them is either getting to much or not enough. Check for air restrictions, nests in the intake system, clogged air filter, wet air filter, oily air filter, gas leaks, etc... you already confirmed good spark so its got to be air or fuel related.
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Old 12-31-2010, 04:43 PM   #20
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In re-reading your original post you mentioned a new manifold. Maybe the gasket is leaking. With engine warmed up and idling, spray carb cleaner along intake manifold gasket mating surfaces, base of throttle body etc,vacuum connections... listen for change in engine idle....could be a slight vacuum leak..
also check the power brake assist for leaks.
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Old 12-31-2010, 05:01 PM   #21
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Did you or do you have any blackness coming out of the front connection where your exhaust goes into the catalitic convertor? Just a thought... On mine, my cat was plugged up bad. Major loss of HP plus when I would accelerate I could hear a "ffffft" sound under there. If your not getting enough air flow throught it, it could cause an issue like yours. Again, just speculation as most of our thoughts at this point!
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Old 12-31-2010, 11:23 PM   #22
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Most of all that timing jargon is controlled by the computer. However, do not forget the basics....fuel, air, and spark. If all those check out then your left with just a few "minor" things..such as grounds,shorts,wife,and the depths of your pocket (hoover flag anyone!?)
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Old 01-01-2011, 10:15 PM   #23
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awesome feedback gentlemen (and ladies, if any)... will update with outcome. thanks and happy new year!!! may it bring your jeeps a trouble free ride.
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Old 01-02-2011, 03:30 PM   #24
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Josi1089 I definitely appreciate the picture and help, hope you get your Jeep up and running soon.
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Old 01-03-2011, 01:30 PM   #25
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+1
Lucas is good stuff.
+2
I put in a bottle every 2000 miles.
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Old 01-28-2012, 09:51 PM   #26
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Any Update?
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Old 03-01-2012, 03:12 PM   #27
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Bump. Any Update????
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Old 12-18-2012, 11:19 PM   #28
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this post is for jibber. sorry it's 9 months (too late), but the culprit was the vacuum hose. mechanics also found out my intake had a hole so replaced that too.
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Old 12-20-2012, 07:31 AM   #29
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this post is for jibber. sorry it's 9 months (too late), but the culprit was the vacuum hose. mechanics also found out my intake had a hole so replaced that too.

Thank You!! I actually sold my YJ. I miss it, but don't miss trying to fix all of the annoying little things.

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Old 05-02-2013, 12:19 PM   #30
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this post is for jibber. sorry it's 9 months (too late), but the culprit was the vacuum hose. mechanics also found out my intake had a hole so replaced that too.
Did they say which vac line it was by chance?

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