2004 Jeep 4.7 HO hesitation and misfire after TB clean?

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Feb 28, 2017
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I've been working on my 2004 Jeep Grand Cherokee Overland w/ 4.7L HO (Getting ready to sell)
FWIW: My daughter drove it for the last 2 years, I never really did. Just fixed a p/s and coolant leak. Still has a very small oil drip (Burns/Drips ~1 qt/ 2k miles), no visible smoke and VERY strong.

Getting it cleaned up, today I pulled the air box and as suspected the throttle body was pretty dirty on the outside and visible lip. I sprayed and wiped it off with Throttle Body cleaner, then opened the butterfly... Backside was covered in black. Just inside was an oily greasy mess. I sprayed and wiped several times as far in as I could reach with my fingers. THEN with the engine running hosed it down with some more TB cleaner, then about 1/3 can of the AMSOIL Power Foam intake cleaning spray. (Similar to the Sea Foam stuff, used it on my lawn mower with no problems).

Then I pulled the PVC valve, it was super gross, almost completely clogged and tons of crap in the tube. Cleaned them out also with TB spray and q-tips.

So I put everything back together. Start-up was a little rough and smoke as expected. Check Engine like blinked for 2 seconds only. Now runs rough as heck. No power at 1/2 throttle, when I floor it it stumbles. Little misfire at idle. I can get it up to 5k RPMs, but power is way down. No check engine light.

Obviously this is opposite of what I was hoping to achieve. What do you all think? Replace the PCV I cleaned? No idea how old the plugs are, at least 50k... Do you think I screwed up the TB or MAF?
 
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Fouled plug. You can use a old toothbrush to clean the TB blade. Soak it and gently hold it open while scrubbing the back side. You might as well pull the plugs since you don't know the mileage on them. I'll bet you got a fouled one because of all the crud that went into the intake. Yes Replace the PCV valve. Good Luck!!!
 
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Did you do an idle relearn procedure? This what I found for Jeeps (completely different from anything I worked on.)

https://www.jeeppatriot.com/threads/ecu-re-learn-procedure-without-disconnecting-battery.42689/

If that dosen't work, I would disconnect the battery (with the engine off)** and let it relearn from scratch (after hooking up the battery and starting/driving it.)**

**Meh, I was going to say something here but decided not to.

Ive never heard of a WJ having to relearn how to idle. This is new to me.
 
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And its a jeep so use the factory type plug, so many silly stories of upgrade type plug fails, should be listed right on hood decal
Yes that’s true I remember we put a little bit higher one in ours because that’s what my dad wanted it didn’t like it at all I can’t remember which ones it was but it didn’t like them
 
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In the future, remove the throttle body before cleaning. Electronic throttle bodies may cut your fingers off, and the butterfly valves don't like being moved around while attached to the car.
 
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I had the same thing happen with my focus. I just cleaned the throttle body and plate on my Focus, as it carbons up enough to make the throttle sticky when closed. I also emptied most of a can of carb cleaner into it while running and the MAF didn't like it. It would idle up near 2k and stayed that way for a couple hours of driving but now the idle is back to normal. I assume the MAF either wasn't used to being clean and the computer had to relearn, or the carb cleaner left some residue that has now evaporated off..
 
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I had the same thing happen with my focus. I just cleaned the throttle body and plate on my Focus, as it carbons up enough to make the throttle sticky when closed. I also emptied most of a can of carb cleaner into it while running and the MAF didn't like it. It would idle up near 2k and stayed that way for a couple hours of driving but now the idle is back to normal. I assume the MAF either wasn't used to being clean and the computer had to relearn, or the carb cleaner left some residue that has now evaporated off..
On my car, at least, the MAF is way before the throttle body. Just take the throttle body out so you can clean both sides of the butterfly plate.
 

Speedbird001

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Feb 28, 2017
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Virginia
Thanks all for the feedback! Really appreciate it. Got a new set of OEM plugs and some boots (No telling how old and brittle the ones on there are). I'm going to give that a go on my day off. Cheers - Patrick
 

Speedbird001

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Update: Thank you all for the advice. I drove it a few more times this week, smoothed out a lot, but not what I was looking for or remember. So I installed new OEM plugs, boot kits and PVC (~$90 total). Two hours later it was running like a top! 290k miles and the 4.7HO is strong.

R&R was not that bad really, rear two took some extensions and one of those super deep spark plug sockets. (Soak w/Kroil the night before probably helped). Def needed the boot/o-ring rebuild kits ($8 /ea) money well spent. Picture below of new and old plugs (Old ones were not OEM and pretty worn).
IMG_9905.jpg
 
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