Hesitation under acceleration - Defender Source
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  #1  
Old June 18th, 2009, 10:55 AM
durangorover
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Chris Wherry
1995 D-90
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Hesitation under acceleration

I'm getting a hesitation when I'm accelerating. I feel it more in 3rd and 4th but it seems to be totally random. It's like it accelerates fine but will skip one beat in there somewhere. The issue doesn't happen or I haven't felt it when decelerating. The rpms don't change(drop) either. I can hear the change in the exhaust a little since I have the top off. I replaced the fuel filter and that didn't seem to do the trick. I've also just recently replaced the water pump, thermo, and belts. Don't know if that had anything to do with it. One of the belts is squeaky on start up though. It's like if you were walking along and someone grabbed the back of your shirt for a second. Any ideas?
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  #2  
Old June 18th, 2009, 11:15 AM
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John
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do the RPM's go up slightly?? clutch slipping??

tends to go in the upper gears first.
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  #3  
Old June 18th, 2009, 11:26 AM
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S. Smith
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Stupid as this sounds, check your driver's side motor mount. My RRC had a broken mount and I was getting odd vibrations from the drive train as well as wierd hiccups from the motor as a result of the motor torquing. Once it was fixed it is smooth again.

Worth a look.
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  #4  
Old June 18th, 2009, 12:39 PM
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Chris Snyder
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Throttle Position Sensor would be my guess. There may be a dead spot in it somewhere. You could test it.
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  #5  
Old June 18th, 2009, 05:29 PM
durangorover
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Chris Wherry
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Clutch isn't slipping and I'll look into the motor mount. I don't know about the throttle sensor. How can you check that?
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  #6  
Old June 18th, 2009, 05:33 PM
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Neil Steinhagen
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Could also be a cheap distributor cap or yours just needs replacing? How long since last plugs, wires, cap and rotor?
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  #7  
Old June 18th, 2009, 07:20 PM
durangorover
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Chris Wherry
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Plugs, wires, cap and rotor are all new and I just realized that I replaced the throttle positioning sensor last summer. I tested to see if it would happen if the car was neutral and revd the engine and it did not happen. I did have the exhaust replaced last year (from behind the cats) but didn't change the O2 sensors. Could this make a difference?
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Old June 18th, 2009, 10:44 PM
durangorover
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Chris Wherry
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Quote:
Originally Posted by durangorover
Plugs, wires, cap and rotor are all new and I just realized that I replaced the throttle positioning sensor last summer. I tested to see if it would happen if the car was neutral and revd the engine and it did not happen. I did have the exhaust replaced last year (from behind the cats) but didn't change the O2 sensors. Could this make a difference?
Sorry I was wrong. I didn't replace the TPS. I replaced the stepper motor. I see if I can get the TPS checked.
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  #9  
Old June 19th, 2009, 02:17 PM
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Hans Haase
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Silly as it sounds, check the vacuum line coming out of the distributor.

Then check your timing as well. Make sure it's advancing when you rev the engine too.

-Hans
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  #10  
Old June 24th, 2009, 10:29 AM
durangorover
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Chris Wherry
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Was out of town for a week so I just got to playing a little more with this issue. Got the TPS tested and it seems to be working just fine. I had some new o2 sensors that I haven't put on yet so I threw those on as well. Went for a test drive and my issue seems to be getting worse. Now its really bad around 2-3k rpm as well as it sounds like the exhaust is very restricted(banana in the tail pipe?). Almost backfired a couple times. Any thoughts? Thanks
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  #11  
Old June 24th, 2009, 11:00 AM
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S. Smith
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Bad plug wires? Sounds like it is misfiring any codes?
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  #12  
Old June 24th, 2009, 12:29 PM
durangorover
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Chris Wherry
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I have new wires, plugs, rotor, cap. As far as I know, no codes. To tell the truth, I've never seen my ECU light up at all. Never seen a code. I adjusted the base idle last fall because of a stalling issue at idle. The one thing I didn't do was check the timing. Could that be it?
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  #13  
Old June 24th, 2009, 12:38 PM
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Trying to backfire says timing to me.
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  #14  
Old June 24th, 2009, 02:03 PM
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Chris Snyder
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Did you ever fix the actual issue causing the stalling? Shouldn't have had to touch the base idle. That might be contributing to this problem.

I would check your timing as well. Maybe the distributor is loose.
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  #15  
Old June 24th, 2009, 02:15 PM
durangorover
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Chris Wherry
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Adjusting the base idle did help the stalling when coming to a stop issue for the most part. It's stalled once or twice since. I haven't adjusted the timing. I don't have a timing light nor do I know how to operate one. I'll check to see if the distributor is loose.
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  #16  
Old June 24th, 2009, 02:29 PM
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Chris Snyder
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Well yeah, it would but only by increasing the idle speed. You just covered up another issue.
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  #17  
Old June 24th, 2009, 07:17 PM
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I had the same problem. After lots of research, I replaced the alternator and the problem was fixed. The cause of the problem was a bad diode. Good luck.
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