Land Rover and Range Rover Forum banner
1 - 20 of 20 Posts

·
Registered
Joined
·
424 Posts
Discussion Starter · #1 ·
Well, my throttle problem has gotten worse, to teh point that I probably can't drive it until I fix it. I further diagnosed it today with a lot of driving.
Here's the symptoms:
It will let me drive at about 5mph (like 1/100th of pressing the pedal down)
Once you go past that point, the throttle cuts on and off repeatedly.
If you put it in neutral while rolling, same effect.
AS SOON AS YOU ROLL TO A COMPLETE STOP as in, the immediate point you go from 1mph to 0, the throttle comes back and acts normal while stopped. I tested this by rolling at 5mph, keeping the throttle at about half throttle, and it would sequentially stumble until I hit 0 then it went right to where it should be and held steady.

Any ideas?

Is there a speed sensor or something? This problem definately feels sounds and appears to be electrical. I was thinking some kind of road speed sensor of some sort.

Do these symptoms rule out the throttle potentiometer? Potentiometer sounds like it would have to do with the speed, but this seems like the spark is being cut off. It seems liek something that sends the signal to give spark, is not workign correctly.

If it helps any, I got goign about 30 down a hill, and it seemed to do the same, but longer pauses between fires.

Thanks for any help.
 

·
Registered
Joined
·
674 Posts
Devon - sounds like it is distributor related...have you swam any streams or large puddles lately???

1. Try a copious squirt of wd40 in the dizzy and see if it helps?
2. Replace your sparkplugs
3. Replace your leads
4. Replace your coil
5. Replace your points

Maybe in that order but not necassarily.

Good luck :drink1:
 

·
Registered
Joined
·
424 Posts
Discussion Starter · #6 ·
havent hit any big puddles really. And this has been going on since I got it.

BTW this is my 89.

If its the coil, that'd be a good thing, i have 2 or 3 others laying around, maybe I should try swapping them? But why would the sparkplugs, leads, coil, etc. act any different when the drivehsafts/wheels are moving, compared to at idle at a complete stop?
 

·
Registered
Joined
·
424 Posts
Discussion Starter · #7 ·
What about that box that is on teh speedoemeter cable , mounted to the chassis near the tranny. Is that a speed sensor? Does that send a signal to the ECU telling it that the car is rolling?
 

·
I'd love to be in the Rat Patrol
Joined
·
3,205 Posts
I like the idea about the throttle position sensor.
Did you swap it yet?
If that doesn't work start swapping the other stuff. One thing at a time. That way we will know what it was.

Is it hard to start?
 

·
Registered
Joined
·
674 Posts
You wrote: But why would the sparkplugs, leads, coil, etc. act any different when the drivehsafts/wheels are moving, compared to at idle at a complete stop?

Something to do with the load on the engine...mine did the same thing - changed the plugs and leads and it went away. I also noticed the same thing after fording a river the other day adn getting water blown into the dizzy from the fan.

:dunno: :dunno: :dunno: :dunno:
 

·
Registered
Joined
·
424 Posts
Discussion Starter · #10 ·
heres what im posting on other boardsnow , i did some work, and figured one thing that it is not, and am getting more and more stumped.

I think there should be some way to diagnose this better than throwing parts at it, as throwing parts gets expensive.

It seems like to me that it has to be a unit malfunctioning, a connection that is bad, or something. It doesn't seemto be a load issue, as it is fine throughout the throttle in neutral at a stop, and has the problem IN NEUTRAL while moving. That kiund of disqualifies a load issue. And the TPS really doesn't make sense because it tests fine (tested with ohmeter by book specs) and the TPS does NOT know anything about the vehicles speed.

Here's the post going to the other boards, if anyone has any info, hlep me out.

Well, this has got me stumped.

1989 Range Rover is the truck.
The trucks symtoms are these:
-If at a complete stop, throttle acts normal (in neutral or park.
-The throttle works fine in drive for about the first 50th of pedal movement, then any more throttle than that the engine cuts on and off repeatedly every second or so, very electrical, like its cutting out spark every so often.
-In neutral while rolling throttle acts teh same, cuts out anywhere past the first point.
-If you hold neutral at say half throttle, going about 5mph, it cuts on and off bouncing the rpm's every half second or so, and as soon as you come to a COMPLETE stop as in the second the wheels are not moving at all, the rpms jump up to where they should be and the throttle acts fine.
-So the symptoms seem to only be there when the truck is in motion.


What I've replaced and thought of:
- I just changed teh speedocable and the cruise tranducer.
-Speedometer does have a little wiggle to it at just about all speeds, but I assume that is teh speedometer gear that often gets worn.
- I don't see how it could be the throttle potentiometer, as that should have no idea if the truck is actually moving or not.
- I just talked to Les at RN on the phone, and he didn't have a clue, he said that the cruise speed tranducer (which I changed) is the only thing that really tells the ecu if its moving or not.

So, does anyone have any ideas or ever had this problem? i'm really stumped, and not sure how to diagnose any further?
 

·
Registered
Joined
·
60 Posts
My best guess would be, ground problem???...have you tried running a lead from battery to body yet. Check continuity from TPS connector to ECM.
 

·
Registered
Joined
·
60 Posts
BTW - my rover used to cut out whenever I turned on the headlights...I know where you're at. These critters are hard to troubleshoot and even harder to sit back and throw parts at.
 

·
I'd love to be in the Rat Patrol
Joined
·
3,205 Posts
This is the craziest thing I've ever tried to figure out.
Only moving? So you can rev the engine from idle to 2500 when your sitting still. But if your moving it cuts out? How full is the gas tank?

Are you willing to put it up on a lift? IF the front is raised where the fuel moves to the back of the tank, just like if you were moving, does it cut out? If so maybe the problem is with the tank or fuel pump? Hell I'm running out of things to guess.

It might be time for some divine intervention.
Maybe if we sacrifice a chicken or two things will get better?

 

·
Registered
Joined
·
424 Posts
Discussion Starter · #15 ·
Hehe thanks guys.

Again, fuel is at half, TPS i have checked and shouldn't make a difference whether i'm moving or not.
Grounds also don't make sense.

Maybe i'll try to take a video today of it...

It shouldnt be the shaking of anything, or sloshing of gas, or anything! Literally, ill be going 1mph, barely feels like moving, and roll to a stop, nothing abrupt at all, and as soon as the wheels stop its fine.

Okie, you are correct about the revving to 2500 thing. It doesn't seem to be a load issue because you can do it in neutral, the only thing I coudl think of is the cruise speed tranducer.

I checked the book, the test for the tranducer is 6 jumps to 12 volts per revolution of the wheel, so it sounds like perhaps its only getting like every 6th jump perhaps?

Otherwise, it's likely that my ecu is the problem. I'm going to do the test on the tranducer today, its either wiring or ecu I suppose?

Does anyone have a 3.9L ecu that I can borrow or buy to swap out and test it?
thanks.
 

·
Registered
Joined
·
60 Posts
Inertia seems to be the only common node of the symptoms you are describing. It may be worth giving the truck a good shake while it's running while sationary to see if the problem emerges....here is another sugestion (perhaps way out there but worth a try nonetheless) - take the filter can off the MAF, then blow some compressed air over the hotwire...see where I'm going with this?
 

·
Registered
Joined
·
424 Posts
Discussion Starter · #17 ·
Can you see the hotwire with the can off? I don't recall.

Another update.

Just took the plug off the ECU sprayed some contact cleaner over the connections wiggled it on and off a few times, then blew it dry with compressed air and put it back together. Took it for a ride, still seemed to be doing it at first, then it went away, like I said it would come and go for the past month and ever since I got it. It worked fine for like 5-10 min of driving, then it came back, but i could use half throttle or above, but anywhere below half throttle it would do it, and by the time i was getting bakc to my houjse it would only work at that very beginnign throttle position so i could go about 5mph.


One question I have no is that, is there any chance that the throttle potentiometer is ONLY used when the truck is moving, which is signaled by the cruise speed tranducer on the speedo cable?
 

·
Registered
Joined
·
60 Posts
TPS values are included whenever the engine is running...Bosch systems (what I am used to working on) have different fuel maps for idle postition, off idle, and full idle positions. Off idle is where the TPS values (along with MAF values) have the most bearing on spark and fuel timing. Not sure if this is exactly how the Lucas system works (probably something along the same lines).

Lonestarrover brought up a good point about wires, over time engine heat dys out and breaks down the wire insulation...then the inner wires usually start to oxidize and your ohmic values go through the roof. From what I've seen wires usually go to piss around the connections, at sharp bends, or at points where they have the opertunity to chaff on the engine, frame or bulkhead. Not that any of this makes bad wires easier to find. It's encouraging to hear that you were able to get your Rover to run better by fiddling with the ECM connector (probably a better signal from something). It may be worth cleaning out all engine bay connectors; put a little dielectric grease on them before snapping them back together.
 
1 - 20 of 20 Posts
Top