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-   -   Rough idle + slight misfire (http://www.wranglerforum.com/f210/rough-idle-slight-misfire-260892.html)

Shane20 08-06-2013 12:49 AM

Rough idle + slight misfire
 
Hello,i have an 06 jeep rubicon 4.0 mt .now that I have more or less figured out my mpg problem I have another issue( not as pressing but still). Went out and fired up my jeep to go to work and every thing was fine when the motor is cold and idle is higher but once the motor reaches operating temp and down it starts idling a bit rough. Now it's not kicking on the mil light nor is it wanting to die but it feel like there is a slight misfire or not getting enough fuel or something. I read in another forum that it could be an issues with heat and where the injectors set into the manifold. Anyone else have this problem.

jeeptjrider 08-06-2013 01:02 AM

I had something to it on both my jeeps one was an O2 sensor and a tps sensor.. People say O2 sensors are never it just try unpluging it and find out which cylinder is miss firing and then switch the injector if the miss fire moves boom found the problem or also check the coil pack check it at night if u see a blue spark arch its a coil pack

Jerry Bransford 08-06-2013 08:43 AM

Starting with the basics, how old are your spark plugs? If they aren't that old, exactly what brand & model spark plug did you install?

James.crawford14 08-06-2013 10:03 AM

That definitely sounds like your TPS. If it kicks the check engine light take it to an auto parts store for a free test

Shane20 08-06-2013 10:09 AM

Quote:

Originally Posted by Jerry Bransford (Post 4045537)
Starting with the basics, how old are your spark plugs? If they aren't that old, exactly what brand & model spark plug did you install?

Plugs are champs 7704 put in a couple of days ago. Also put all four new o2 sensors in with NTK brand. I pulled and cleaned the IAC and ran a bottle of 44k in it. Only real weird thing in all that was when I replaced the coil boots and inner springs, the very front boot spring was hard to pull out so I ended up stretching it and it finally came out. I put the new stuff on and they seemed to fit nice so IDK if I my have damaged it.

Shane20 08-06-2013 10:10 AM

Quote:

Originally Posted by James.crawford14 (Post 4045810)
That definitely sounds like your TPS. If it kicks the check engine light take it to an auto parts store for a free test

No mil light. I have a scanner and nothing came up

Shane20 08-06-2013 04:14 PM

Update: I went ahead and replaced the IAC and TPS and still did not fix the problem I'm now starting to wonder if my injectors are getting heat soaked

James.crawford14 08-06-2013 04:17 PM

Hmmmm did you look in to your distributer at all

Shane20 08-06-2013 04:44 PM

It's a DIS system

xxBOsoxFANxx 08-07-2013 10:00 AM

Quote:

Originally Posted by Jerry Bransford (Post 4045537)
Starting with the basics, how old are your spark plugs? If they aren't that old, exactly what brand & model spark plug did you install?

I'd go with Jerry on this one (because he helped me through a similar issue). I noticed with mine that I had one plug that was gapped just a hair off and caused my misfire. If it isn't your plugs, it could be a heat soak issue. I had to replace the heat shield under the injectors on mine, old and falling apart. I also placed a sleeve around the number 3 injector. I think there is a thread on here with part numbers. The DIS is very finicky I've come to notice.

Shane20 08-07-2013 01:02 PM

Quote:

Originally Posted by xxBOsoxFANxx (Post 4050023)
I'd go with Jerry on this one (because he helped me through a similar issue). I noticed with mine that I had one plug that was gapped just a hair off and caused my misfire. If it isn't your plugs, it could be a heat soak issue. I had to replace the heat shield under the injectors on mine, old and falling apart. I also placed a sleeve around the number 3 injector. I think there is a thread on here with part numbers. The DIS is very finicky I've come to notice.

Does that sleeve cover the 06 4.0, I thought it was for the 02-04 models

Shelby427 08-07-2013 08:34 PM

Not going to say it isn't, but the more common problem with the injector shields was a hot soak problem. After the vehicle was driven, parked for a bit, and then restarted.
Would cause a fuel starvation problem, like vapor lock. Making hard to start, running poorly until enough cool fuel got through the injectors. Can't say I remember it causing a problem in normal driving.

I'm with Jerry, always start with the basics.

Shane20 08-07-2013 10:16 PM

Quote:

Originally Posted by Shelby427 (Post 4052275)
Not going to say it isn't, but the more common problem with the injector shields was a hot soak problem. After the vehicle was driven, parked for a bit, and then restarted.
Would cause a fuel starvation problem, like vapor lock. Making hard to start, running poorly until enough cool fuel got through the injectors. Can't say I remember it causing a problem in normal driving.

I'm with Jerry, always start with the basics.

I'm using champs

Shane20 08-07-2013 11:30 PM

Quote:

Originally Posted by Shelby427 (Post 4052275)
Not going to say it isn't, but the more common problem with the injector shields was a hot soak problem. After the vehicle was driven, parked for a bit, and then restarted.
Would cause a fuel starvation problem, like vapor lock. Making hard to start, running poorly until enough cool fuel got through the injectors. Can't say I remember it causing a problem in normal driving.

I'm with Jerry, always start with the basics.

I'm using champs 7704 I think. There double plats the dealer sold me

Shane20 08-07-2013 11:38 PM

Update: took her to a friends shop and scanned it. Well it looked like the voltage didn't change during the misfire to the injectors ( that does not rule out an injector going bad) but it seems like there really dirty according to him, so I'm going to run an injection system flush and see if that helps

Jerry Bransford 08-08-2013 09:46 AM

I seriously doubt your injectors are dirty, I would bet big $$$ flushing/cleaning the injectors won't help at all.

Champion 7704 plugs are the wrong model, 7034 is the right double-platinum model Champion spark plug for newer distributorless engines like yours.

Shane20 08-08-2013 06:43 PM

Quote:

Originally Posted by Jerry Bransford (Post 4054196)
I seriously doubt your injectors are dirty, I would bet big $$$ flushing/cleaning the injectors won't help at all.

Champion 7704 plugs are the wrong model, 7034 is the right double-platinum model Champion spark plug for newer distributorless engines like yours.

I could not remember the number 7034 are what I put in

Shane20 08-28-2013 09:48 PM

Update: well the idle is still rough. I gapped the plugs again and ran some 44k thou it, and that helped for a little. Still can't seem to pin point the problem. It never stalled out it just seems to me like a misfire. I'm hoping to find the cause soon

R u s s 08-29-2013 02:26 AM

Quote:

Originally Posted by Jerry Bransford (Post 4054196)
I seriously doubt your injectors are dirty, I would bet big $$$ flushing/cleaning the injectors won't help at all.

X2 This guy is a smart cookie ;)

I have yet to see with my own eyes injector cleaner work if its to the point there not spraying right it is time to replace them.
As for your slight miss it could be injector going bad or coil starting to fail. I would lean more toward coil.
Try a different set of plugs. I had an outboard do the same thing and figured out it did not like platinum plugs it ran better with old school no frill spark plugs

Shane20 09-07-2013 12:11 PM

Update: I ended up putting on a new coil ( I dropped it ) and still idling rough.
I'm still thinking it has to do with the fuel injectors.

kdawgg11 09-07-2013 12:22 PM

Quote:

Originally Posted by Shane20 (Post 4369937)
Update: I ended up putting on a new coil ( I dropped it ) and still idling rough.
I'm still thinking it has to do with the fuel injectors.

How is it doing when driving any missing or backfires or doing anything while driving?

Shane20 09-07-2013 03:21 PM

Quote:

Originally Posted by kdawgg11 (Post 4370057)
How is it doing when driving any missing or backfires or doing anything while driving?

well.. it drives great, no rough idle,no mis,nothing

Shane20 09-10-2013 10:53 AM

Well we had a big temp drop were I live ( roughly 20 degrees colder ) and my jeep was running pretty good. The misfire and rough idle was still there but hardly noticeable. So I wonder what it could be?

kdawgg11 09-10-2013 04:48 PM

Quote:

Originally Posted by Shane20 (Post 4446049)
Well we had a big temp drop were I live ( roughly 20 degrees colder ) and my jeep was running pretty good. The misfire and rough idle was still there but hardly noticeable. So I wonder what it could be?

I wish I could help you but I don't know I wonder if there is a air/temp sensor that could do that? I doubt it what about o2 sensor I will think more about it but I am unsure

Shane20 09-11-2013 10:47 AM

Quote:

Originally Posted by kdawgg11 (Post 4454697)
I wish I could help you but I don't know I wonder if there is a air/temp sensor that could do that? I doubt it what about o2 sensor I will think more about it but I am unsure

All foyer o2 sensors are new

Reznor 09-11-2013 11:57 AM

I'm actually running into a very similar issue on my 03 Sport, though my miss occurs at all times from startup to fully warm. No CEL. I'm debating buying a rebuilt injector set. Have new plugs, new coil, cleaned throttle body, air filter, checked TPS.

If you haven't done that last thing, give it a shot. Easy to do - you can backprobe the connections with a multimeter. The center one is ground, one will have constant 5v(ish) power, and one will move from very low up to around 5v depending on throttle position.

chevymad 09-11-2013 10:15 PM

My 03 runs a bit rough at idle as well. I've cleaned the injectors twice in the last year and both times it runs much smoother afterwards but it only lasts for a month or so. I've also noticed on a couple trips that if I buy fuel with no ethanol that it will also idle smooth. Eventually I'm going to replace the injectors, since cleaning them does seem to alleviate the issue for awhile.

Jerry Bransford 09-11-2013 10:31 PM

I'd bet more on one or both of your upstream 02 sensors being bad, I really doubt your fuel injectors have anything to do with your rough idle.

rkulp89 09-12-2013 05:49 AM

Quote:

Originally Posted by Jerry Bransford (Post 4496681)
I'd bet more on one or both of your upstream 02 sensors being bad, I really doubt your fuel injectors have anything to do with your rough idle.

I'm having a rough idle issue that vibrates the cab to the point that the mirrors shake. The engine feels like it stutters every few seconds but never dies. When I hit the gas everything smooths out and runs great. I've cleaned the IAC, swapped plugs, and plan on testing the TPS. Do you think the O2 sensors would be worth changing? I don't understand why the engine is rough while at idle but runs great while driving. I just got the jeep (04 unlimited), not sure if it should be idling like this or not.

Reznor 09-12-2013 11:02 AM

Here's the thing about the O2 sensors, and why I ruled them out in my own situation:

Firstly, there is no CEL. This doesn't necessarily mean they are not at least somewhat faulty, but is a good start.

But when a vehicle is first started, it runs in open loop - completely bypassing the O2 sensors until it warms up and then goes into closed loop. So if the idle/running occurs when the vehicle is dead cold, then it shouldn't be the O2 sensors.


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