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Unread 10-14-2013, 03:06 PM   #121
KiloWatts
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I did this today. Mine was pretty dirty - not quite as dirty as OP's, but still dirty.

Honestly I didn't notice a huge change. But I have had a couple intermittent stalls over the past week, so let's see if this fixes it.

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Unread 11-11-2013, 09:23 AM   #122
broclirobb
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Very good information OP, Thanks for the write-up! I just did this too this weekend, but haven't hooked it back up yet. I sent out my throttle body to get bored out while its out. But my question is, I've seen multiple posts on this thread saying to make sure you disconnect you battery first.... I didn't. It is still connected right now with the 3 plugs unplugged at the throttle body location. I'm at work now so I can't go disconnect until I am back home tonight. But why is this necessary? Is this just to reset the computer to allow relearning (which I plan to do during re-installation) or is it so I don't fry something? (I hope not!)
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Unread 11-11-2013, 07:30 PM   #123
MaintMech
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Your battery holds enough energy to to great damage to anything it's connected to.

You have very old and (possibly) damaged wiring.

Unless you want to spend big $$$ repairing something you swear you never touched.....


ALWAYS disconnect the battery when messing with wiring!


Heck, the first thing I do when working on my Jeep is isolate the battery.


Yes, even for something as simple as an oil change.

OCD can be your friend.
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Unread 11-12-2013, 06:27 AM   #124
broclirobb
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Quote:
Originally Posted by MaintMech View Post
Your battery holds enough energy to to great damage to anything it's connected to.

You have very old and (possibly) damaged wiring.

Unless you want to spend big $$$ repairing something you swear you never touched.....


ALWAYS disconnect the battery when messing with wiring!


Heck, the first thing I do when working on my Jeep is isolate the battery.


Yes, even for something as simple as an oil change.

OCD can be your friend.

Thank you for the quick reply, this makes much sense and I think is good that somebody clearly stated why you should do this. I disconnected the battery this morning.
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Unread 11-30-2013, 02:53 AM   #125
paragrunt
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Thanks OP for the write up. I found it on a google search. I had a check engine light that was bugging me, slightly higher RPM at idle and even worse fuel economy that usual. I replaced the IAC Valve & The TPS. When I took off the IAC valve, I used brake cleaner on a ton of q-tips and cleaned the nasty 14 year build up of carbon and soot out of there. I then installed my new AEM Dryflow short ram CAI on it and she purrs like a kitten.

I bought my 00 XJ with 65k on it and plan on keeping it until the wheels fall off.
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Unread 03-06-2014, 09:41 AM   #126
whitedog1
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This is a helpful thread, but I still have questions, but first the history:

1998 Jeep Cherokee Classic, 4.0, 192XXX miles.

Friend called me to tell me his 17 Y/O daughters Jeep died and won't restart. He also mentioned a cloud of black smoke. Checked it out and the alternator was bad. Fixed that and he wanted me to change the engine oil. While doing that, I saw the plug wires were old so I pulled a plug and the needed changing, so I did the plugs, wires, cap and rotor. (OOPS... 153624 not 153642, but that was easy)

So that's the history. Start it up and it idles much smoother with the plug wires correct, but after a few minutes, it was running rough a bit and surging a bit. not at all what it should be. So I pull out my scanner and there are no codes. Ok...

I know this girl has a cracked exhaust manifold, so I look at the 1/1 O2 sensor and it is running at .28-.32 volts and it says LEAN. So I figure that the leaking exhaust manifold is causing the O2 sensor to see a lean condition so it keeps adding fuel until it loads up and runs like dog doo. Pull the exhaust manifold and weld it up. While the intake was off, I pull the throttle body and clean that then I clean the IAC. While cleaning the IAC, I did pull the shaft out, but I could hear and feel the motor turning rather than the gears strip.

Question #1: What position should the IAC valve be in when you pull it off? On the ones I have seen, they were always seated fully, but this one was off the seat about 1/8 inch.

So I get it all back together and it still runs like dog doo after a few minutes. I reset adaptations for fuel and IAC and whatever else adaptations were in there with zero change. I use my scanner and I go into tests and it will step up idle speed in 100 RPM increments and that works just right, so I hesitate to say the IAC is bad.

Other things to note: I check manifold vacuum and when running smooth, vac was at about 14"Hg. but when running rough, it's at 11"Hg. It is my understanding that low vacuum can be caused by retarded timing. Since it runs at 14" sometimes, I hesitate to think the rings are so worn it's effecting vacuum, plus it starts and runs great other than idling. I did look at ignition timing with the scanner and it was bouncing from 20 something to about 7 so this is suspect.

Question #2: What else will cause the surging, the low vacuum and the fluctuating timing.

OH, one last thing: I am a 25 year mechanic, but a diesel mechanic, so this spark ignition stuff is still on my learning curve.

I didn't expect this to be a PhD dissertation, and I hope that you have read through this and can help me or at least point me in a better direction.

Doggie Thanks you.
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Unread 03-07-2014, 06:56 AM   #127
PolkaPower
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A bad computer can cause it.
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Unread 03-07-2014, 09:19 AM   #128
whitedog1
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Do you know what the signal from the O2 sensor should look like?

Also, could the cat be bad?

EDIT:

Found this post by greasefingers: http://www.jeepforum.com/forum/f13/o...y-want-508460/

It looks like I am getting a signal from the O2, it's just running lean. Time to start plugging off vacuum ports to see if I can isolate this.
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Unread 03-08-2014, 07:49 AM   #129
ZeeJay1997
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Quote:
Originally Posted by whitedog1 View Post
Question #2: What else will cause the surging, the low vacuum and the fluctuating timing.
restricted exhaust, with a clogged cat being suspect. the cracked manifold / lean condition is a cat killer.
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Unread 03-08-2014, 01:43 PM   #130
whitedog1
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Quote:
Originally Posted by ZeeJay1997 View Post
restricted exhaust, with a clogged cat being suspect. the cracked manifold / lean condition is a cat killer.
Aha. So the cracked manifold allowed too much air in and it killed the cat because it kept over-fueling. The dead cat is causing a restricted exhaust which caused it to start running poorly after a few minutes.

Does that sound like exactly what you just said, just differently?

Any opinions on aftermarket cats?
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Unread 03-08-2014, 07:00 PM   #131
ZeeJay1997
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Quote:
Originally Posted by whitedog1 View Post
Does that sound like exactly what you just said, just differently?

Any opinions on aftermarket cats?
that's correct. if you have a scope scanner, you should be able to monitor the front and rear sensor to determine the efficiency of the cat. the rear sensor should have a narrow wave around .5 volts while the front sensor produces (approximate) a .2 to .9 waveform centered at .5v. you can also test it with an IR gun, but i dont know what parameters you need to look for.

i put a flowmaster on mine and it was melted in 9 months. i have no other opinions.
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Unread 03-11-2014, 12:11 PM   #132
Uniblurb
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Quote:
Originally Posted by ZeeJay1997 View Post
that's correct. if you have a scope scanner, you should be able to monitor the front and rear sensor to determine the efficiency of the cat. the rear sensor should have a narrow wave around .5 volts while the front sensor produces (approximate) a .2 to .9 waveform centered at .5v. you can also test it with an IR gun, but i dont know what parameters you need to look for.

i put a flowmaster on mine and it was melted in 9 months. i have no other opinions.
From what I've read, along with videos watched, the inlet end of the cat housing should be 100 degrees cooler than the outlet temp. At least that's what I went by in using my IR gun and supposedly if the temps are near equal the cat isn't doing it's job in burning up fumes.
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Unread 03-12-2014, 09:48 AM   #133
whitedog1
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All this talk of dead cats reminds of a joke...

How do you make a cat sound like a dog?

Dip it gasoline and light it on fire. It will go "WOOF".

(No cats were harmed in the telling of this joke)
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Unread 04-02-2014, 06:43 PM   #134
elijahpr
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Awesome write up, thanks! When you clean the throttle body on your 5.2, did you remove it completely? I cleaned my IAC, and the place it goes into, but couldn't really get to much else without removing the throttle body.
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Unread 04-17-2014, 07:27 PM   #135
Mjczj
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Important Adjustment Check on IAC

I cleaned my IAC for low idle with no change. Was about to order new part but saw adjustment instructions from Airtex on Rock auto site. Part should extend no more than 28mm or 1 1/8 inches. Made the adjustment to this spec and runs like new with 170K!



Follow instruction on this link: http://www.airtexve.com/custom_searc.../990700385.pdf
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