Rough Idle - JeepForum.com
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post #1 of 19 Old 03-24-2017, 01:54 PM Thread Starter
Bedlam_YJ
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Rough Idle

Hey guys. It's been a while since I was last here asking for the blessing of the Jeep gods.

I looked through some of the older rough idle posts and none of them really describes the problem I'm having exactly, but I got some tips of what to look at next. Here's the scoop:

Started the Jeep this morning and noticed it was idling very rough. Lots of vibration in the tub. Turned it off and back on. Same thing. Drove just fine yesterday. Thinking it was just cold, I drove it to work. Drives like it normally should: No major vibrations while moving down the road. Temp is good, oil pressure is average. Same thing happened when I was getting ready to leave this afternoon. Started it, rough idle, lots of a shaking. I popped the hood and the engine is shaking pretty good; more so than usual. There's some backfiring from the exhaust when revving, but once it clears 1200 RPM, it's smooth sailing. Sounds like a possible timing issue.

Drove it to the parts store and picked up some new spark plugs (they needed to be changed anyways). Pretty good carbon buildup on the first 4 plugs, less so on the last 2. Still getting a rough idle.

I'm waiting on a ride to take me back up there but figured Id ask you guys to see if there should be anything else glaringly obvious I should check. The wires are fairly new (bought last year) and it's been nuttered. Gonna grab a new o2 sensor, 2 new PCV valves for the valve cover, see if they have an EGR in stock, grab a can of carb cleaner for the Weber, and pick up a new fuel filter.

Anything else you guys can think of to check or grab? Trying to minimize the number of trips I have to make so as not to be a burden on my ride.

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post #2 of 19 Old 03-24-2017, 02:21 PM
Jeepsr4me
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pull the throttle body off and the idle air valve and clean them.... Its very common and very easy to do..

You tube 4.0 TBI cleaning and you will get a bunch of good ones... Watch a few and then get a 10 mm and torx bit and have at it...
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post #3 of 19 Old 03-24-2017, 03:09 PM Thread Starter
Bedlam_YJ
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Quote:
Originally Posted by Jeepsr4me View Post
pull the throttle body off and the idle air valve and clean them.... Its very common and very easy to do..

You tube 4.0 TBI cleaning and you will get a bunch of good ones... Watch a few and then get a 10 mm and torx bit and have at it...
It's a 1987 4.2 YJ with a carb, there is no IAC.
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post #4 of 19 Old 03-24-2017, 04:09 PM
dancytron
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If you've Nuttered it, the O2 sensor isn't hooked to anything, so replacing it won't help.

Unless it is leaking or stuck open, the EGR isn't it either. Test it before you buy another one. If it is stuck open, you can usually just clean them and it fixes the problem.

http://home.sprynet.com/~dale02/egrvalve.htm

If you are going to throw some parts at it, then Distributor cap and rotor. You can user better Ford parts. http://www.jeepforum.com/forum/f8/i-...nitive-669495/

You are using regular copper plugs? Don't use fancy platinum ones.
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post #5 of 19 Old 03-24-2017, 05:43 PM Thread Starter
Bedlam_YJ
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Quote:
Originally Posted by dancytron View Post
If you've Nuttered it, the O2 sensor isn't hooked to anything, so replacing it won't help.

Unless it is leaking or stuck open, the EGR isn't it either. Test it before you buy another one. If it is stuck open, you can usually just clean them and it fixes the problem.

http://home.sprynet.com/~dale02/egrvalve.htm

If you are going to throw some parts at it, then Distributor cap and rotor. You can user better Ford parts. http://www.jeepforum.com/forum/f8/i-...nitive-669495/

You are using regular copper plugs? Don't use fancy platinum ones.
Yeah, I picked up regular copper core plugs. I know the older vehicles don't take too kindly to the platinum ones. Tore apart the carb and gave it a proper cleaning; no help there except that it looks a lot nicer. I figured that the o2 wasn't going to do any good after realizing the nutter completely negates it. Tried to edit the thread, but the page kept hanging so I just left it.

I was going to do the distributor cap and rotor before, but never got around to it. Still have the rotor in the jeep, just need to see if I can find a blue cap and not one of the black ones. No daylight left here, so everything else is going to have to wait until tomorrow. Looks like it's down to PCV valves, distro, wires (doubtful), and fuel filter (dunno). I'll check for vacuum leaks with some carb cleaner tomorrow. Thanks for the replies so far guys. Keep them coming!
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post #6 of 19 Old 03-25-2017, 02:49 PM Thread Starter
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Parts are ordered from the parts store. Will be in tomorrow. I'm going to go outside and test the spark plug wires and reconnect my headlight relay mod. Maybe I'll think of something else to check while I'm under the hood. Would like to get this fixed before Monday, as I have to drive...
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post #7 of 19 Old 03-25-2017, 04:12 PM Thread Starter
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May be on to something. Started the Jeep and unplugged spark wires one by one. Big changes when 1, 2, and 3 are unplugged. Very little change when 4, 5, and 6 are unplugged. Distro? Rotor? The wires are getting spark. I can hear it jumping when holding the wire close to the plugs. Adjusting the vacuum advance doesn't help either; only hinders.
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post #8 of 19 Old 03-25-2017, 11:35 PM
Theman1945
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You said it has been nuttered...

Is it connected to manifold vacuum or ported/timed vacuum? IF it's connected to the wrong one, maybe this is causing the rough idle at low rpms which away as the vacuum changes. Maybe try switching it real quick to see if your problem goes away?

1988 YJ OKSJC
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post #9 of 19 Old 03-26-2017, 07:58 AM Thread Starter
Bedlam_YJ
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Quote:
Originally Posted by Theman1945 View Post
You said it has been nuttered...

Is it connected to manifold vacuum or ported/timed vacuum? IF it's connected to the wrong one, maybe this is causing the rough idle at low rpms which away as the vacuum changes. Maybe try switching it real quick to see if your problem goes away?
Yeah, I nuttered it about 5-6 years ago. Don't think that it would explain the sudden change in idle 2 days ago, but I'll give it a shot and see if it helps. I also tested for vacuum leaks at all my hoses yesterday; no dice there either.
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post #10 of 19 Old 03-26-2017, 02:08 PM Thread Starter
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Just got done doing the Team Rush upgrade. It must've been the rotor/distro. The rotor was pitted and had some gnarly scoring on it and there was some kind of residue or condensation on the under side of the cap. After installing the parts and checking all the vacuum lines and caps again, everything is running fine. Sorry to cause a clutter with another useless thread, guys. Thanks for your help!
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post #11 of 19 Old 03-27-2017, 01:26 PM
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Quote:
Originally Posted by Bedlam_YJ View Post
Just got done doing the Team Rush upgrade. It must've been the rotor/distro. The rotor was pitted and had some gnarly scoring on it and there was some kind of residue or condensation on the under side of the cap. After installing the parts and checking all the vacuum lines and caps again, everything is running fine. Sorry to cause a clutter with another useless thread, guys. Thanks for your help!
That's a pretty good upgrade, but consider HEI someday
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post #12 of 19 Old 03-29-2017, 12:48 PM Thread Starter
Bedlam_YJ
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Originally Posted by mike134 View Post

That's a pretty good upgrade, but consider HEI someday
Got any thread links handy? I'm not in town right now and so no computer is handy. Searches are easier for me on a PC vs. a phone.

What kind of benefits are there to doing an HEI upgrade? When I get back, I'm going to throw the taurus electric fan in place of the mechanical one. May as well look into doing HEI at the same time.
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post #13 of 19 Old 03-29-2017, 02:41 PM
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the Team Rush upgrade gives you better quality tune up parts to the existing system. The HEI is a more powerful more reliable spark system. It replaces the spark coil, distributor, and I think the ICM as well.

The recommended HEI distributors on the forum are from CRT (usually purchased on eBay) or DUI (which is a way way more expensive brand). It is a very easy swap, you can save it for your next tune up so you don't waste the money from the team rush upgrade. the CRT HEI will run you about $120. I believe this is the one you want, but better check with someone else (the company) for confirmation: CRT HEI (ebay)

Whether an electric fan is better/worse depends on who you ask. What is your goal with it?

The other major upgrade as far as reliability goes is switching the stock Carter carburetor to something significantly better. Motorcraft 2150 or Weber are the forum leaders here. I think the motorcraft 2150 will run about $250-300. It is much easier to tune and maintain than the stock Carter carb. This isn't really a pressing matter though.
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post #14 of 19 Old 03-30-2017, 08:37 AM
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Whether an electric fan is better/worse depends on who you ask. What is your goal with it?
I only liked because Chris did.

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post #15 of 19 Old 03-30-2017, 09:51 AM
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I only liked because Chris did.
I think all of the "improvement" comes from the stock fan clutch being locked up and malfunctioning before the e-fan swap, in which case people notice a "HuGe HoRsEPoWeRZZ GAINZ!!!"

Although I'll say that there's nothing wrong with going to an electric fan (with the addition of a bigger alternator), but its easier to just fix what you've got.
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