3.9 Cuts out for short period of time - Defender Source
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  #1  
Old September 14th, 2014, 06:27 PM
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3.9 Cuts out for short period of time

Just recently my 3.9 will randomly stall/cut out almost completely for about 2 seconds and then come back to life.

Mostly when I am in 3rd gear running about 2500rpms.........it's like you pull your foot off the accelerator quickly for a second and then bam, it comes back to life. (what it feels like, not what actually happens).

Really crappy description, but hopefully you get the idea.

Any idea what it might be?
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  #2  
Old September 14th, 2014, 06:35 PM
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Sounds like the magnetic pic-up air gap is not right. Check spec.
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Old September 14th, 2014, 06:46 PM
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thinking horses not zebras ,., have you checked the air hoses ... the big plenum one can cause this if its loose.
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Old September 14th, 2014, 07:04 PM
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Third guess ignition switch intermittent failure
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I don't know about the brakes, only their unreliability.
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Old September 14th, 2014, 07:24 PM
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Ooo a wild guess thread, I'll play

Broken motor mount, pulling the coil wire tight, engine stalls and sits down, coil wire connections restored
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Old September 14th, 2014, 08:51 PM
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Quote:
Originally Posted by leastonce View Post
thinking horses not zebras ,., have you checked the air hoses ... the big plenum one can cause this if its loose.
Intake Hose?

Nope, tight.




No broken mounts or tight wires.


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Old September 14th, 2014, 09:12 PM
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Is the issue repeatable?

If it is then maybe you have a bad spot on your throttle position sensor.

Rover gauge would diagnose that nicely by a multimeter measuring the resistance would be a second option.
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Old September 14th, 2014, 09:20 PM
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Quote:
Originally Posted by leastonce View Post
Is the issue repeatable?

If it is then maybe you have a bad spot on your throttle position sensor.

Rover gauge would diagnose that nicely by a multimeter measuring the resistance would be a second option.
Random, but repeatable.


Just drove a 600 mile trip with no hiccups, then all of a sudden it started. Not every time I get into 3rd, but randomly repeatable.
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Old September 14th, 2014, 09:58 PM
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Any codes on the ECU?
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Soapy water / KY jelly, etc. is is basically a must. Yes, good idea to remove trim panels - only takes 5 more minutes to do so.
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Old September 14th, 2014, 10:06 PM
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Quote:
Originally Posted by leastonce View Post
Any codes on the ECU?
Not right now.

It had 48 on it which I think is Idle related..........the little sensor has been clogged up before. erratic idle, etc.....
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  #11  
Old September 14th, 2014, 10:12 PM
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On the air gap thought...it's a lot like point gap of old. There are worn out bearings involved here. That's normal for sure. If I remember right the spec on these is like .009-.014. That's pretty tight. Wide gap equals short dwell time an narrow is opposite. The swing or spec comes from known wobble. It makes a world of difference when you can hit the middle around .011. Easy to set but don't just check in one spot. Rotate the crank one turn or dist. A half turn. I've seen this random issue before. Good luck
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Old September 14th, 2014, 10:45 PM
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Bad ignition switch? (or is that just a Series problem?)
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Old September 15th, 2014, 01:47 AM
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Quote:
Originally Posted by Firemanshort View Post
Bad ignition switch? (or is that just a Series problem?)
Hey no stealing my guess, (post 4), I wanna win the prize!!!!!
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A friend of mine runs a land rover / range rover specialty repair shop. Based on his experience, they are capable of stopping anywhere, anytime, at any cost.

I don't know about the brakes, only their unreliability.
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Old September 15th, 2014, 10:54 AM
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Quote:
Originally Posted by Firemanshort View Post
Bad ignition switch? (or is that just a Series problem?)
It's just a GM problem ...
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Soapy water / KY jelly, etc. is is basically a must. Yes, good idea to remove trim panels - only takes 5 more minutes to do so.
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  #15  
Old September 15th, 2014, 12:03 PM
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Ignition module
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Old September 15th, 2014, 12:25 PM
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Hey these are all pretty good! All over the board. We'll figure out what it isn't long before figuring out what it is and where all the prize money goes.
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Old September 15th, 2014, 12:34 PM
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I'll vote for the wiring harness that goes to the fuel pump on its way out. Is it happening more and more often?
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  #18  
Old September 15th, 2014, 04:29 PM
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It has only happened like three or four times over the last couple of weeks.

Ignition module is easy enough to switch out I guess. This truck has an interesting ignition switch set up. It has a toggle switch that turns the truck "on" and then a start button. Not any kind of key switch. I suppose one of those could be bad but I kinda doubt it.
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  #19  
Old September 15th, 2014, 08:29 PM
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So I have had this scenario twice in my decade or two owning my truck. The first time was the ignition switch which you have ruled out. The second time was the alternator. Yep, alternator. You can search for the threads here, but the jist of it is that I had some A/C bleed into the wiring harness which throws off the fuel injectors when it gets to a specific amount/frequency/rpm. It was always RPM specific and I believe it was 2400 rpm or there abouts.

Zenier diode went bad. Fixed it and the problem has been solved since. Very difficult to find that cuprit...

So, worth checking. You can start by putting your multimeter on AC and seeing if you get anything, or take it to an autoparts store. Bench testing is best.

Just an idea---good luck.

(BTW, if it is warm enough to get really hot where you are, definitely take a look at your ignition module. If it hasn't gone bad, it will, and it usually manifests when it gets hot. This is one of the symptoms, as is staying stalled and not restarting for a few. At very least, relocate it if not already done so).
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  #20  
Old September 18th, 2014, 09:24 PM
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Small update.

I have not had any time to really screw with this thing, but it has gone from intermittent stallings/shutdown to completely cutting off.

I rolled the dice and drove it today to work just trying to see what all happened. Early when the truck was cold this morning sure enough I hit 3rd and it starting cutting out.

On the way home from work, same thing........hit 3rd and it lost power/cut out. Less than 1/8 mile later it stalled completely. I pulled over and it would turn over and start for less than 1 second and then shut down. I did this for about 15 times thinking I was going to have to say screw it and go get my trailer, but eventually it started, ran fine and I got home.

Anyway, I'll add that to the "story" and see what other ideas you all might have.
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