Somewhat rough idle ? (NO NOT COIL)

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jbrown91

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Hello, I have an 04 V8 with 132k on it. I just recently purchased it less than a month ago and have been working it out. I had an 00 V8 prior so I know a lot of the problems with the V8. Here's what I've done:

New Motorcraft plugs
Replaced two coils that were bad
  • Siliconed all boots
  • Di-electric grease on inside of boots
  • Properly seated springs and boots
  • Everything properly torqued and seated
MAF Cleaned
TB Cleaned
New Fuel Filter
Cleaned K&N air filter
Reset KAM

I know it seems crazy but I still couldn't get it perfect so I've did everything perfect. I've used a Snap-On Solus Pro to help diagnose my problems. There AREN'T any misfires with the system and other than my noticeable idling the engine is 110% perfect on everything.

Symptoms:
Slightly rough idle, you can feel a little "shake"
It becomes much more noticeable at 1350 - 1400 RPMS

It isn't anything bad but it does leave a little hesitation on acceleration.

I've narrowed it down to IAC or something TB related. The TPS is good and both are showing good numbers. 24.5 on TP1 and .8 TP2. TP1 moves down and TP2 moves up on acceleration.

There are no misfires, no codes, no NOTHING..... This is driving me nuts. It is such a small issue that it really shouldn't be crazy to figure it out but I like things perfect. I also don't want to replace the whole engine to try and figure it out. So any help is MUCH appreciated!

Ohh btw, yes I did search extensively and couldn't find anything relevant.
 
its a coil....i recently had the same issue, the coils were about a year old ebay coils. I had a slight hesitation and no CEL, well i decided to change out the coils and everything is good now. The car runs like a dream....trust me its a coil issue.
 
Exhaust gas recirculation (EGR) valves are famous for causing rough idlle. But, any EGR problem should trigger a "check engine" light.
 
02LS8Lincoln said:
its a coil....i recently had the same issue, the coils were about a year old ebay coils. I had a slight hesitation and no CEL, well i decided to change out the coils and everything is good now. The car runs like a dream....trust me its a coil issue.
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Yeah, I would think that. But like I said, I'm able to look at the misfire counts with the scanner. Since the two coil's have been replaced, no misfires.

I thought about the EGR as well, but you are exactly right on the CEL will pop up IMMEDIATELY if there is an error. My F-150 has had the light on for a year, just haven't changed the EGR. Truck runs great.

Anyway to know if the IAC is bad?

I may have to wait it out and see until whatever is wrong "causes" a problem. Since the car thinks it is perfectly healthy.
 
Your 04 LS doesn't have an IAC (surprised that you didn't notice that), so you can eliminate that as a suspect. I vote coil too. Otherwise, you might do compression and leak-down tests on each cylinder.
 
It doesn't have IAC? I actually never looked and just assumed it did. I'm thinking about doing compression on each cylinder, I just hate taking the cams out... It gets old taking those valve covers off..... How could it be a bad coil if I drove with it, heavy acceleration, and watched the monitor continuously with no misfire counts?
 
jbrown91 said:
It doesn't have IAC? I actually never looked and just assumed it did. I'm thinking about doing compression on each cylinder, I just hate taking the cams out... It gets old taking those valve covers off..... How could it be a bad coil if I drove with it, heavy acceleration, and watched the monitor continuously with no misfire counts?
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Misfire counts are not 100% accurate. That's why the Ford TSB says to stress test the coils, and not to go by the internal diagnostics.
 
I actually don't have an oscilloscope. Could you use a good OHM meter or should I buy an oscilloscope?

Also, I don't think the Solus does that, it may need an extra accessory... I don't really know.
 
jbrown91 said:
I actually don't have an oscilloscope. Could you use a good OHM meter or should I buy an oscilloscope?

Also, I don't think the Solus does that, it may need an extra accessory... I don't really know.
Click to expand...

An ohm meter is nothing like an oscilloscope. I don't think that you understand the failure mode of these coils. A resistance reading won't tell you anything about high voltage breakdown.
 
I do understand how these work, but I don't have a cheap ohm meter, it does a lot of reading. I get about the high voltage break down and how it fails. I don't know where to get an oscilloscope to use and I'm still not sure if it's on the Solus Pro.
 
jbrown91 said:
I do understand how these works, but I don't have a cheap ohm meter, it does a lot of reading. I get about the high voltage break down and how it fails. I don't know where to get an oscilloscope to use and I'm still not sure if it's on the Solus Pro.
Click to expand...

A million dollar ohm meter still can't tell you what a $500 oscilloscope can.
A $10,000 oscilloscope still won't tell you much if you don't know what the waveforms mean and aren't used to using one.

At $50 a coil, the simple way out is to replace all the coils and plugs (again). This still may not be your problem. You could have an injector issue or an internal engine issue. When buying a car, new or used, I pass on all of the ones that aren't perfectly smooth. I've dealt with enough engines to know that some individuals just aren't smooth and can't be corrected without a full teardown. Let's hope this isn't the case for you.
 
Well, I'll just have to let it play out. I've reset the KAM and swapped around coils multiple times and everything seemed fine. I'll just have to wait and see if it gets worse probably. I hope there isn't an internal problem, but I do know where to get two gen II v8's... Thanks for the help.

BTW no, I've never used an oscilloscope. I haven't had to use it on anything. I may just have to get help from my friend that is a mastertech, just hate asking him for help. Thanks again though.
 
I wish you good luck. Let us know if you work it out. I've got a little roughness in my 04 (at idle only) that I haven't been able to get rid of. I think it may be an injector, but it's not bad enough to go hunting for. (It was okay when new.)
 
joegr said:
I wish you good luck. Let us know if you work it out. I've got a little roughness in my 04 (at idle only) that I haven't been able to get rid of. I think it may be an injector, but it's not bad enough to go hunting for. (It was okay when new.)
Click to expand...

Thanks, it probably is as you say. I'm just really picky I guess and like things to be at least mechanically perfect. But until it gets worse, I guess I need to stop thinking about it..... Thanks for the insight, helps a lot when I'm not thinking outside the box.

The coils will have to wait before I'll drop $$$. So I'll wait like you said until it gets "bad" (when the car notices it's wrong). Thanks again
 
jbrown91 said:
The coils will have to wait before I'll drop $$$. So I'll wait like you said until it gets "bad" (when the car notices it's wrong). Thanks again
Click to expand...

just a warning, the car may never notice when it gets bad, there have been many many cases where the misfire is very noticeable and it never triggers a CEL, or even the car basically shuts down all power because it thinks its a different problem.
 
Guys... recently ran into a similar issue on my 06 LS. Rough IDLE (you can feel the shake) and when you accelerate its sluggish and the transmission is now shifting at higher RPM points (3000-4000rpm) than before. NO Check Engine Light NO Codes. Changed out all the coils to the 'latest' (-BE) Motorcraft and cleaned the throttle body with carb cleaner but hasn't fixed it.
 
^ to the guy above.

Is it cold in your location during these symptoms?

I chased coil/plug problems for months before discovering my intake manifold (the plastic) had leaks.
 
Kind of cold...between mid-30s-50sF. Really appreciate this lead. How did you finally get to the intake manifold as root cause (carb cleaner sprayed on manifold,...?) In addition to the rough idle (shake) were you also getting high rpm shifts?
 
I got a new code recently, P0357, Ignition Coil. Have had rough idle lately, bad gas mileage, slow takeoff. Going to use YourMechanic.com again, they just put a new starter on my Ford truck. I've replaced the coils once, when I first bought my car a few years ago. Have put about 40k miles on since then.

Now I'll search for Joe's coil part number, IIRC he said the Motorcraft is a good part now after redesign.
 
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