Tech Help - 1994 YJ - Jerky, Sputtering Mess After Warm - JeepForum.com
 
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post #1 of 6 Old 08-24-2011, 10:19 PM Thread Starter
SkepticalChymst
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1994 YJ Wrangler 
 
Join Date: Jan 2011
Location: Scottsdale
Posts: 6
Tech Help - Fixed - 1994 YJ - Jerky, Sputtering Mess After Warm

** FIXED! YAY! **

The Fix

Dirty or Loose Wire Coupler from Power Distribution Center to Fuel Rail.

The Story

My Jeep has not been happy since the CK run. On the way home from it, right before I got to the highway it started acting up. It would sputter and buck when accelerating. At first it would only do it a little bit. But then after a while on the Highway it would do it more. If I stayed a constant speed it was fine. If I accelerated very slow through the gears it was fine. And I mean very slowly. If I tried to accelerate normally it would sputter and buck but would be fine once I got to whatever speed I chose to stay at.

I made it home ok but It continues to do this. But only after I have driven it for a while. the hotter it is outside the faster it seems to happen. I can make it to work in the morning without it doing it much. I can make it home but it does it more. I have a very short drive to work, about 1-2 miles or so.

Jeep Info
1994 Jeep Wrangler
4.0L I6
about 100k miles on it.
New Parts in Last 6 Months or less:
Fuel Pump, Fuel Filter, Battery, Spark Plugs Wires Rotor and Cap. Catalytic converter.

Symptoms Summary

Sputters and Bucks Under Heavy Load. Like Acceleration or using a higher gear then would be ideal. Like trying to re-accelerate from 4th gear after slowing down to like 20 MPH or so.
Does not exhibit symptoms when engine is cold and has been sitting overnight.
Exhibits symptoms much less after sitting in covered parking all day and Driving home.

Testing Done So Far
Visual Inspected Everything. Found nothing disconnected. Nothing broken.
Replaced Fuel Filter
Performed Fuel Pressure Test with engine off. 32 PSI - Normal
Performed Fuel Pressure Test with engine running at idle. 32 PSI - Normal
Performed Fuel Pressure Test with fuel pressure regulator vacuum line disconnected. 38 PSI - Normal
Checked Resistance on all fuel injectors. All within the normal range of 14.5-15.5 ohms.
Disconnected Oxygen Sensor - No change
Disconnected MAP (Manifold Absolute Pressure) Sensor - Jeep Ran Worse.
Checked Rotor and Cap. Its good. (6 months old or so.)
Checked all spark plug wires and spark plugs. They are good (6 months old or so.)
Air intake is not obstructed. Air filter is not new but is not overly dirty.
No Codes on OBD1 System. (Except normal 55 code)
Engine Runs Fine at Idle.
When its hot I can give it a little gas at idle and get it to do it but it goes away quickly as I give it more gas.

Things I Plan To Do Still
I've been told to test the MAP (Manifold Absolute Pressure) Sensor, TPS (Throttle Position Sensor), and Oxygen Sensor. But I have not had time yet.

Things I'm Assuming / Know Based on Testing
Fuel Filter is Good.
Fuel Pump is Good.

If anyone has any other ideas for me to try It would be greatly appreciated. Thanks for reading.


Last edited by SkepticalChymst; 08-25-2011 at 04:57 PM. Reason: Fixed
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post #2 of 6 Old 08-25-2011, 04:56 PM Thread Starter
SkepticalChymst
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1994 YJ Wrangler 
 
Join Date: Jan 2011
Location: Scottsdale
Posts: 6
By happy accident the problem was found! A friend of mine was poking around looking for issues while the engine was running and moved the power wire coupler that goes to the Fuel Rail out of the way and the engine died. Every time we would fiddle with that wire the engine would die or sputter. We pulled the connector apart, cleaned it and put it back together and now the problem is gone. I drove the jeep around today during the hottest part of the day and tried everything i could to make the problem come back. I even messed with the wire a bit to see if I could get it to do it again and I can't.
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post #3 of 6 Old 08-25-2011, 10:31 PM
oldtime_ironman
Web Wheeler
1991 YJ Wrangler 
 
Join Date: Dec 2010
Location: 14304 Niagara Falls
Posts: 2,537
Be sure to re-set the computer by disconnecting the battery for 5 mins. Unhooking sensors won't make any change because the computer is in "default" mode. Re-setting it forces it to re-learn what your setup actually is, and run with that.

I tend to be a jerking sputtery mess when I'm warm too.

.

Last edited by oldtime_ironman; 08-25-2011 at 10:33 PM. Reason: joke
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post #4 of 6 Old 08-26-2011, 06:08 AM
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit
Posts: 20,798
Thanks for posting this up. There are far too many threads that people dont post up the fix.
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post #5 of 6 Old 09-04-2011, 09:17 AM
blade81
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Join Date: Sep 2011
Location: new johnsonville
Posts: 1
I have a 94 wrangler that is doing exact same thing. Can u tell me where that wire harness is exactly please. Thanks
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post #6 of 6 Old 09-05-2011, 10:42 PM Thread Starter
SkepticalChymst
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1994 YJ Wrangler 
 
Join Date: Jan 2011
Location: Scottsdale
Posts: 6
These are not the best pics but here ya go. Its basically the connector that feeds power to the fuel rail.


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