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Topic: 4.0L Stalling/Bucking while driving

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LEAD_NOT_FOLLOW
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4.0L Stalling/Bucking while driving
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1993 XJ w/4.0L and AW4 with 130K on it. Only motor mods are an aftermarket intake.

At idle it runs a bit rough. While driving it will stall/buck/miss a bit. Looses power when it bucks as well. Exhaust sounds "raspy". Seems like I can feel it kick back into the power, and will run fine for a bit, than goes right back to missing.

Only thing I've done lately was fill it up with a higher grade of gas than I normally do. I was bucking a bit at idle prior however. It has gotten progressivly worse however. Took it to Fort Wayne (about a 45 min trip one way) tonight to take Rebecca out to dinner for her B-Day and though we were not going to make it back home. Anything over 55 it won't handle at all, if I baby it at 45 it'll do ok. RPM's do not seem to flucuate while it does this.

I'm going to change the plugs/wires tomorrow and see if that helps. I really don't have a tone of money to throw at it to get it fixed; however it's our "family" rig at the moment so I need to resolve the problem ASAP.

Anyone have any thoughts? I havn't had a single issue with it since we purchased it. Replaced the original water pump last summer, but it's ran smooth as silk since we've owned it.


Here is the list of things I've come up with;

- Bad Fuel (aka water in it?)
- Bad Plugs/Wires
- Bad Fuel Pump
- Bad Fuel Filter
- Bad O2 Sensor
- Clogged Cat
- Bad TPS (will test tomorrow)
- Bad CPS (doubtful)

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firehawk
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I'd try spraying some carb cleaner around the intake/throttle body gasket while it's running. It would tell you if it's a vaccum leak. I'm no expert, but it kinda sounds like a vaccum leak.

MY next step would be to replace the fuel filter.

-- Edited by firehawk at 22:34, 2009-01-23

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threeEs99
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Its your TPS. I'll bet my Jeep on it. They are around $70.00 or $40.0 at junk yard for the whole throtle body. Spend money on TPS first, not the tune up. Unless you have noticed any cracks in cap. Moisture gets into TPS and destroys it. I've had this problem twice. Once in my YJ and once in my XJ. You can also check it with a DVOM, sorry dont know perameters(sp) off hand.
-- Edited by threeEs99 at 00:00, 2009-01-24

-- Edited by threeEs99 at 00:01, 2009-01-24

-- Edited by threeEs99 at 00:03, 2009-01-24

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99 sport.
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04 wj (w/3 car seats too)
DD duty for the lady  
LEAD_NOT_FOLLOW
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I've got the TPS info on the tech page; http://www.greatlakesxj.com/tech/TPS.html


It's on the top of the list to check. I plan on messing around with it this afternoon after Maitlyn's Upwards B-Ball Game. Will report back later...

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mvusse
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Except for the rough idle, it sounds a lot like what mine as doing. Mine was a fuel delivery problem from a plugged sock on the fuel pump. The pump was also incredibly loud. New sock, pump is quiet and truck runs good again.

It is also possible the timing is off, but I wouldn't know how as it's not adjustable. At least it's not on the older (90 down) ones. Don't know much about the newer (91 up) ones yet, as I just got my 94 XJ earlier this week.

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LEAD_NOT_FOLLOW
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I don't think it's the fuel pump, nor do I think I have a vaccume leak.

Replaced plugs, wires, and the cap today. Cap physically looked OK untill I pulled it off. One of the prongs fell compleatly out and looked like it wasn't making any contact. So I'm hoping that I found the problem.

While doing that, I manage to bust the heater control valve (yeah for bitter cold!). Local supply store said they had it in stock, drove across town to find out they don't. Nobody else has one locally. They say they'll have me one by 6PM tonight, we'll see...

So untill I get the new heater control valve in I can't start it.

Havn't messed with TPS yet, figured I'd see if plugs/wires/cap solved the problem first.

Will update later tonight...

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mvusse
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If you're talking about the vacuum controlled heater control valve under the hood, just take it out, splice the hoses together with whatever you have laying around and stick a golf T in the vacuum line. The valve is not needed.

Heater temperature is controlled by a door that directs airflow through and deflects air around the heater core. I have not noticed any ill effects from having the valve disabled, even in summer.

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mvusse wrote:
If you're talking about the vacuum controlled heater control valve under the hood, just take it out, splice the hoses together with whatever you have laying around and stick a golf T in the vacuum line. The valve is not needed.


Heater temperature is controlled by a door that directs airflow through and deflects air around the heater core. I have not noticed any ill effects from having the valve disabled, even in summer.

Renix and HO valves are different. It's a vital item on the 91-97 HO motor. In 98 they did away with it and changed the way the hoses were ran.

Plus not having coolant run threw the heater core in the summer months I only hope helps preserve the life of it. Swapping out a heater core in the XJ/MJ is not a fun job. So $20 in my opinion is money well spent to replace it.

 



-- Edited by LEAD_NOT_FOLLOW at 16:13, 2009-01-24

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threeEs99
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Have you pluued any codes? Usually a code pops up for a faulty TPS. Dont know if you can do so on yours, but cycling the key used to get codes on my 95 YJ.

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Got it put back together tonight before it got to dark out.

Drove it around the block and not doing it. Will mess with it further tomorrow, but as it stands now looks like the plugs/wires/cap have solved the issue. We'll see once I get it on the highway on the way to church in the morning...

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xjryder
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Your headlight fluid might be low , check your conooter valve , J/K

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threeEs99
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Inspect your muffler bearings and be sure to do all final torques with a metric liquid wrench.
Call the local parts store and ask cleark for pricing on a 1968 VW bug, water pump and theromistat.

-- Edited by threeEs99 at 15:42, 2009-01-25

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99 sport.
rust bucket, DD, 3 car seats
04 wj (w/3 car seats too)
DD duty for the lady  
LEAD_NOT_FOLLOW
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threeEs99 wrote:
Its your TPS. I'll bet my Jeep on it.
I'll expect your XJ sitting in my driveway no later than Tuesday by Noon. You've got the address.... evileye


Looks like plugs/wires/cap solved the issue. Plugs didn't look to bad, wires looked ok, cap didn't look the best however. No cracks or anything, but one of the terminals was loose and coroded (sp?) really bad. Anyways, runs like a champ again.

 



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threeEs99
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We didn't shake on it. You can drive it at Haspin though. Maybe show me how to really use it. From your discription it sounded exactly what I've experianced a couple times. I was close on condition of cap. Maybe you should do more maintance on your vehicles. LOL

-- Edited by threeEs99 at 09:53, 2009-01-26

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99 sport.
rust bucket, DD, 3 car seats
04 wj (w/3 car seats too)
DD duty for the lady  
LEAD_NOT_FOLLOW
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threeEs99 wrote:
You can drive it at Haspin though. Maybe show me how to really use it.
I'm gonna hold you to it; the saying your coming to Winterfest part... biggrin

 



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