Rough idle at start, then smooths.

[coolwind57]

This issue showed up a few weeks ago.  Engine runs really quite rough after start, but after a minute or two smooths out and purrs like a kitten.  Yesterday, this rough idle (sounds kinda like its not firing on all cylinders) lasted considerably longer and took about 2-3 miles of driving before it cleared up.  

 

I hadn't had the chance to look into it yet, but this morning and at lunch today I'm getting the same thing.  Runs rough for 2-3 miles before taming out and running well.  I do feel a loss of power during the time it is running like hell.

 

What's my first check?  Idle Air Control Valve coking?  intake leak,  maybe?  What would you guys do with this symptom.  My copper plugs are probably a bit over a year old.  Taylor Thundervolt 8.2mm in 2018.  

 

 

You know, I think it would be nice if we had list of symptoms and troubleshooting guide maybe on a sticky.  Would be nice for members to quickly search and find solutions and tricks to problems like this as they creep up.  Just a thought, Pete.  Would help with redundancy in answering member's questions too.    

[cruiser54]

That's okay. We're from the Department of Redundancy Department.

 

Check your intake bolts. IAC would cause stalling. Not a miss. 

No ticking noises along with the miss? 

MAP to throttle body hose integrity?

[54bobby]

mine has don that since i've had her. snapped off exhaust manifold studs. i liken her to a line from tommy lee jones in space cowboys when he's describing the SR71 Blackbird.

"down here on the ground she leaks oil and hydraulic fluid all overbut get her up to 80,000 feet and all the seals swell up , and she just" I forget the rest, any how, that's what my 4 angry squirlls do, when she warms up the metel swells up and stops the cooler air from getting in and she just purrs. Ok, maybe i might have bin a little base when comparing my 242,000 mile 2.5 to the SR71,  the SR71 has floor boards.

[coolwind57]

On 7/22/2021 at 3:59 PM, cruiser54 said:

That's okay. We're from the Department of Redundancy Department.

 

Check your intake bolts. IAC would cause stalling. Not a miss. 

No ticking noises along with the miss? 

MAP to throttle body hose integrity?

I did swap out to another IAC after cleaning it all.  No changes.

 

Sometimes I do get ticking for a minute or two,  as if a lifter is temporarily dry but it goes away promptly.  I've been experiencing this for years though.

 

Intake bolts are SO HARD to get to.  I attempted the other night, but ran out of time.  Took out the breather box and still cursed and hollered like a crazed lunitic.  I'll take another shot at it maybe tonight or tomorrow.  MAP to throttle is good, and it's all new hoses and elbows about a year ago.  I disconnected at MAP and engine promptly died. 

 

I'll pick up some new plugs on the way home after work as soon as I remember what Copper plugs I used.  I think I went with something different that what Jeep recommeded back in 1989.  They're probably 2-3 years old  I'll see how each of my old plugs look as I pull them.

 

Anything else come to mind, fellas?  

[cruiser54]

NGK plugs. 

 

How's the inside of the distributor cap look? 

 

Have you put a wrench on the topmost, easy to get to, intake bolts?

[coolwind57]

On 7/26/2021 at 1:20 PM, cruiser54 said:

NGK plugs. 

 

How's the inside of the distributor cap look? 

 

Have you put a wrench on the topmost, easy to get to, intake bolts?

Pulled the distro cap and cleaned well.  Removed deposits from electrical contacts, which I was sure to be the problem.  There was certainly buildup.  My cap is a napa copper, so a cleaning and not replacement was in order.  

 

I got to all intake bolts on the top side and only a couple on the bottom before giving up.  Only an exhaust-only bolt seemed looser than expected.  None of this solved the problem.

 

Last night I pulled the plugs.  They all looked the same, none being oily or burned.  Replaced with new NGKs.  Popped in an air filter.  BAM!  Looks like this took care of my problem.  Runs smoothly upon startup now.  I recall cruiser54 saying that plugs should be changed every 30k and I suppose that was all that was needed to fix this issue.

 

Thanks to everyone for participating in my post.  Funny thing:  After getting it all fixed and was swelling in pride, I turned my headlights on to check on alignment.  As I switched to brights, I lost them.  Neither low/high come on now.  Perfect.  I love my MJ, but she keeps me on my toes ALWAYS.  haha   More troubleshooting after work tonight.  It never ends!

[cruiser54]

Cap, rotor, plugs and wires every 30K.