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Author Topic: 98 zj, it runs but stalls.  (Read 1435 times)

Offline jwebb1998

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98 zj, it runs but stalls.
« on: January 02, 2015, 05:38:06 PM »
Finally got it started.  New battery, new calipers, pads and rotors. new fuel pump, new plugs, oil change and a little oil on the cylinders as well as a few cranks of the engine by hand to make sure its not siezed.  7 years of sitting on the sidelines and she lives.  Moved under her own power today.  But she stalls out unless i keep my foot on the throttle just a little bit. Italso wont start right up unless i bump the pedal a little.  After keeping it running for 10 minutes or so i took my foot off the throttle and it almost stayed running at about 500 rpms but it still cut out after a few seconds.  Any ideas?  Maybe a clogged fuel filter?  But im under the impression the filter is part pf the pressurr regulator, which i thought was part of the fuel pump which i just replaced.

Oh well tomorrow is another day.

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #1 on: January 02, 2015, 05:48:48 PM »
2Nd thought, how long do you guys think it would take for all the old fuel that was in the lines to run through amd be burned off, it almost seems to get better the longer i keep it running.  But ive had it running for 20 minutes now.

Offline Posimoto

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Re: 98 zj, it runs but stalls.
« Reply #2 on: January 02, 2015, 06:59:06 PM »
How much old fuel did you have in the tank? I didn't see that you clean/replaced the air filter, engine needs to breath. IAC valve could be dirty as well.
"That's the trouble with research on the internet, there's no way of verifying its truth" --Abraham Lincoln

71 CJ5 V6/T14/D18/Warn OD (from CO)
79 CJ5 304/T-150 Silver Anniversary
79 CJ5.5 360/T-18/4.1 D-300
77 CJ5 360/T-18/3.15 D-20
77 CJ7 258 Fuel Injected T-18/D-20 (from CO)

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #3 on: January 02, 2015, 07:34:27 PM »
Forum wont let me upload pics from my phone.  But i drained and cleaned the tank, so the only old fuel was in the lines.  I forgot to buy an air filter when i was at the store, so i removed the old one just to be sure it was getting air.  Going to pick up an air filter and pcv valve tomorrow.  I ended up keeping it running for 30+ minutes and it finally stopped stalling.  Drove it down the street to top it off, seems to be running great.  But it is still a rough start, i either need to bump the throttle or let it crank for a few to start it up.  Its not throwing any codes, which is a huge plus.  IAC valve?
« Last Edit: January 02, 2015, 07:35:06 PM by jwebb1998 »

Offline Twisty

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Re: 98 zj, it runs but stalls.
« Reply #4 on: January 02, 2015, 08:26:48 PM »
I agree with Chuck regarding the IAC.  If it stalls without your foot on the throttle, I would replace the IAC (Idle Air Controller) motor.  It's a little electrical valveish thing on the side of the throttle body that the computer controls to allow the RPM to be ~1100rpm when cold, but do drop to 700rpm when warm.
88 MJ buggy, 4.0/AW4, 203/205, 3 link front/4 link rear on airshocks, 42" Iroks, full hydro

"Only wealthy men can afford to buy cheap things."

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #5 on: January 03, 2015, 02:32:02 AM »
It stopped stalling, just has a rough start now.  It either starts real rough or I need to bump the throttle to get it to fire up right away.

Offline Posimoto

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Re: 98 zj, it runs but stalls.
« Reply #6 on: January 03, 2015, 07:43:07 AM »
The Idle Air Control (IAC) is just that, it controls the idle air. The IAC has moving parts that have been sitting in one position for 7 years in your engine. It could be sticky from carbon buildup and could possibly just need a cleaning.
"That's the trouble with research on the internet, there's no way of verifying its truth" --Abraham Lincoln

71 CJ5 V6/T14/D18/Warn OD (from CO)
79 CJ5 304/T-150 Silver Anniversary
79 CJ5.5 360/T-18/4.1 D-300
77 CJ5 360/T-18/3.15 D-20
77 CJ7 258 Fuel Injected T-18/D-20 (from CO)

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #7 on: January 03, 2015, 10:48:59 AM »
Well I think the IAC is fine now, like i said its running fine.  My only problem now is the rough start, not to sure what would cause that.  Starts after several seconds of cranking or fires right up if i hit the skinny pedal.

Offline Twisty

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Re: 98 zj, it runs but stalls.
« Reply #8 on: January 03, 2015, 11:04:58 AM »
Probably the IAC not opening enough, and like Posi said, it's likely gummed up.  You can take it off and try to clean it, but replacing it will be the most surefire way to make sure that it's working properly.
« Last Edit: January 03, 2015, 11:05:55 AM by Twisty »
88 MJ buggy, 4.0/AW4, 203/205, 3 link front/4 link rear on airshocks, 42" Iroks, full hydro

"Only wealthy men can afford to buy cheap things."

Offline jps4jeep

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Re: 98 zj, it runs but stalls.
« Reply #9 on: January 03, 2015, 11:13:53 AM »
Spray throttle body cleaner into that throttle body. X4: you probably gave some humming on the IAC motor. That should help with extended cranking starts. I would also recommend removing the fuel rail and injectors and soaking them in solvent and new O rings. Sitting for 7 years with fuel in them is not a goos thing. All the fuel treatment in the world will not thoroughly clean them out.
Dad always said "If it has boobs or spark plugs it will be fun AND will cause you problems."

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #10 on: January 03, 2015, 03:05:58 PM »
Drove the jeep home today, it did sounds good.  Im looking into cleaning the IAC now.  I will also clean the fuel rail as mentioned.  But im wondering what kind of solvent i should be soaking it in. 
The jeep is now sitting at my house and i dont need it on the road before april so i will give it as much low budget tlc as possible.  Anything at all that i can remove, clean, maybe slightly rebuild and put back on, now is my time to do it.  So i can pick up new o rings for the fuel rail and clean the rail itself?  I know you said to spray some throttle body cleaner in there to clean it up, but would it benefit from a full removal and cleaning to get as much junk as possible out of there?

I will pretty much do anything at this point i really want to get this thing running right.  It might be 17 years old but it sat for 7 years and only has 82k on it, so im hoping it will last me awhile. 

Thanks for dealing with my newb questions and all the help so far.

J

Offline jps4jeep

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Re: 98 zj, it runs but stalls.
« Reply #11 on: January 03, 2015, 03:19:26 PM »
There are several options, really depends on who you ask as to which is the best. Some people use seafoam, some use specific objectors cleaner and some use a fuel treatment. Little Google searching and a trip to the parts store will help you decide.
O rings, Napa had them when I last bought them ten some odd years ago, dealership definately has them.
Dad always said "If it has boobs or spark plugs it will be fun AND will cause you problems."

Offline Posimoto

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Re: 98 zj, it runs but stalls.
« Reply #12 on: January 03, 2015, 03:45:44 PM »
x2,

I used seafoam, other produces may be just as good. Use a fairly new tooth brush in the TB.



Should look something like this on start up.

"That's the trouble with research on the internet, there's no way of verifying its truth" --Abraham Lincoln

71 CJ5 V6/T14/D18/Warn OD (from CO)
79 CJ5 304/T-150 Silver Anniversary
79 CJ5.5 360/T-18/4.1 D-300
77 CJ5 360/T-18/3.15 D-20
77 CJ7 258 Fuel Injected T-18/D-20 (from CO)

Offline jps4jeep

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Re: 98 zj, it runs but stalls.
« Reply #13 on: January 03, 2015, 03:58:04 PM »
Summit sells an o ring kit for $7
Dad always said "If it has boobs or spark plugs it will be fun AND will cause you problems."

Offline jwebb1998

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Re: 98 zj, it runs but stalls.
« Reply #14 on: January 09, 2015, 08:19:36 AM »
x2,

I used seafoam, other produces may be just as good. Use a fairly new tooth brush in the TB.



Should look something like this on start up.



Did you remove it to clean it?  I read somewhere its a bad idea to.  But my TB is positiined up and down and im afraid if i dont remove it all the crap i clean off of it will go into the motor.


 



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