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JesusIsLord
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Discussion Starter · #1 ·
Hi Guys, I've been working on a few ideas about what would be the cause of this problem. My '99 Discovery 4.0 has had an intermittent problem with stumbling and sometimes stalling but it only occured either at stops or starts. With this in mind and looking on this and other sites for possible fixes I replaced the stepper motor among other things.

Last week I took a quick 5hr trip to Ft.Lauderdale and noticed that along the way at appx. 75MPH it would loose power and stumble for about 10 seconds or so and then pick up speed again. This happened about 3 times during my return trip. When I got back I did a little more research and found that this particular pattern also occurs when the Vehicle Speed Sensor is going bad. Now before I go out and spend the $100 to have one sent to me I'd like the forums 2 cents on this fix.

Does this sound like a possible solution? Thanks for your input.:buttrock:

BTW this is what I've done so far:

New Magnacore 8mm plug wires
New plugs (Bosch Platinum) I know about the controversy here...
Cleaned PCV oil separator
New Stepper Motor
 

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Former LR tech, Albany NY
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2,437 Posts
Do you have any codes. It should throw a code.

Also check fuel pressure. it should remain constant at 40 psi. Turn the car off and check to see the fuel pressure doesnt drop.

It should stay around 34 psi.

If it drops you got a problem
 

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Beezel, although I respect the fact that you work at a dealer and probably know more about fixing rovers in your pinky than I do in my whole arm, but when mine did this, it didn't throw a code. Based upon the fact that he didn't mention a code being thrown and it was happening intermitently, I think it might be a simplier fix like the fuel filter. Also, if he hasn't changed it in a while, it is a good idea to do that anyway. IMHO, of course.
 

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When it's dark out side, pop the hood and see if the plug wires are arcing to metal brackets around the engine. It takes a minute for your eyes to adjust, but just stare at the wires for a few minutes in total darknes.

But, I put my money on carbon build up.....

Do you get a check engine light after a long trip? Does it reset after severl starts? Do you get a mis-fire code?
 

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Premium Member
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roverX said:
Ooooooo...never thought of a carbon build-up. Good call Dan. Nothing some BG44K can't cure...
If you are goit to use the 44K, buy their 3 pack, 44K for the fuel, their t/b cleaner and their induction cleaner. After cleaning the induction cleaner, turn off the engine and let it sit for 1/2 hour, then drive the crap out of it.
Good luck.
Mike J.
 

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131 Posts
Speed Sensor symptoms

For what it is worth, I have a 97 Disco. Shortly after I bought it, I'd be driving along and at random, it would loose power. I replaced the fuel pump since it was a common problem and the Disco had about 100, 000 miles on it. The problem continued. I replaced the speed sensor and all was fine. (Replacing the speed sensor requires some contortion to get your arm up around the exhaust, over and down and with thumb and forefinger trying to fit and turn a hex screw which goes in at an angle...just so you'll know...)

Hey...if I didn't love this vehicle.......I don't know what it is about them. Maybe like Everest...its the challenge.
 

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Hank said:
When it's dark out side, pop the hood and see if the plug wires are arcing to metal brackets around the engine. It takes a minute for your eyes to adjust, but just stare at the wires for a few minutes in total darknes.

But, I put my money on carbon build up.....

Do you get a check engine light after a long trip? Does it reset after severl starts? Do you get a mis-fire code?
yeah i always take a windex bottle full of water and spray around. If there is a grounding/arcing problem you'll see its acring around ALOT more than just by itself
 

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JesusIsLord
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185 Posts
Discussion Starter · #11 ·
These are all great suggestions. I'll try the fuel filter first as it's the most painless. I haven't replaced it and I'm not sure if the previous owner did. The plug wires are new and unless they are chaffing on some exposed metal I doubt they'll be arcing. I'll check tonight though just to be sure. As for the "check engine" light or any codes, there hasn't been and there isn't any... Just an intermittant problem that's got me scratching my head.

I've heard some comments on the Bosch Platinum plugs. Do they allow carbon buildup because they don't burn as hot as the NGKs? Just wondering. I've also seen in other posts that these engines do get carboned up pretty easy. I've only put 93 octane fuel in it since I bought it and the previous owner did the same to help combat this.

Thanks for all the replies. I'll keep you posted:D
 

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No, those plugs don't do that. I have 50,000 miles on my Bosch plugs. I last ran a bottle of 44K when I did the change out. I am getting ready to do it again just a maintenance.
 

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If it were a seppd sensor, his Speed-o would also go nuts when it's missing.

The 44K stuff won't help, either. This is an exhaust valve problem. Once the carbon is built up, the only cure is to remove the valves and either clean or replace them.

Strange your not getting a mis-fire code, though.
 

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Speed Sensor

When my speed sensor was going out, the speedometer acted fine. An easy way to determine if it is the problem is to unhook the wiring going to it. The speedometer will not work, or the odometer, but if you drive around for long enough and don't have the same problem, then it is the speed sensor going out. (it sends feedback to the fuel pump and is supposed to shut it off when there is an indication that the motor is running too fast...not technical jargon, but someone else might explain it better....in short...if the system senses things turning too fast, the fuel pump shuts off temporarily). It doesn't cost anything to unplug it unless you get a speeding ticket. :)
 

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JesusIsLord
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185 Posts
Discussion Starter · #18 ·
VSS (Vehicle Speed Sensor)

Hi Guys, I finally figured out the problem. My speedo started to fluctuate between 0-35mph at idle and it gave me a clue as to the cause. I ordered the VSS from Atlantic British ($108USD w/shipping) and installed it. I've been driving it for a couple of weeks now with no problems! Woohoo:buttrock:

Just wanted to let you all know. Thanks for the great tips:D
 

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stalling....

9dawgs said:
Hi Guys, I finally figured out the problem. My speedo started to fluctuate between 0-35mph at idle and it gave me a clue as to the cause. I ordered the VSS from Atlantic British ($108USD w/shipping) and installed it. I've been driving it for a couple of weeks now with no problems! Woohoo:buttrock:

Just wanted to let you all know. Thanks for the great tips:D
I have been having what seems to be the same problem. How hard was it to install the speed sensor, and can you give directions?

Thanks!.

I am basically stalling, but only when the car gets warm. If I can get it moving, it doesnt give me problems unless I stop and then durig idling...
 
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