Intermittent speedo fault

[Will Thompson]

Hi Guys

Many threads on here regarding this matter but no definitive answers and people with different symptoms ie not working at all.
Now 4/6 months ago my auto box packed in and I had a manual put in, now everything works as it should except my speedo now has an intermittent fault that for example when doing 50mph the speedo will show 75 then all of a sudden the speedo will drop off back to normal but this may take 5 mins or even an hour to do, my odo works fine my rpm gauge works fine. Now my power steering pump as been leaking and same with my transfer case so there has been a lot of oil everywhere so i don't know if this has gone in the speed sensor and given me the fault or is that not possible? what i cant get my head around is why its only intermittent surly nothing should work. I have seen people checking the ground wire at the back on the intake and i cant see any broken wires there.
Any advice would be greatly appreciated.
This a 1hz jap import btw if that makes any difference what so ever.

 

[leonard_nemoy]

The tachometer needle will sometimes jump a little on mine and even read off by a few hundred rpms, it only happens to me when I am driving fast on the interstate on a very windy day. I think it has to be a loose wire somewhere moving in a strong breeze.

 

[Woofythewolf]

Remember it's not necessarily a broken wire, mine was a loose bolt holding the wire. (so tugging on it would made it seem like a good connection)

Normally it worked, but when the engine hit specific RPMs it would vibrate just right where it was completely losing connection at that frequency and, losing the ground generated a signal of a different frequency that mixed with the real one, resulting in pretty high readings on the ODO.

The problem could be worse on a diesel I think because it vibrates more, and the lower RPMs would result in a lower displayed reading.



For the sensor itself, it's hard to say. If it's the same as the autobox sensor (a sealed rotary encoder), then drowning it in oil wouldn't hurt anything.

If it's an inductive pickup sensor, then oil with metal shavings/powder would leave the metal on the magnetic tip and weaken/make the signal unpredictable. (that would on the internal side though, so I don't think that could be it).

 

[Will Thompson]

The ground connection is solid behind the intake but had some oil and grease etc around there, I have given the ground point a rub down and clean. I have stripped this all back as far as i can and there are no loose wires as far as i can see. I have taken it for a drive... same old doesn't work properly but everything else is working. left it running for 5 minutes gone back again for a drive and it works fine the car hasn't even got up to running temp......

 

[Will Thompson]

i have been reading this thread: #1 Speed Sensor Tests OK - Pics I am a little confused about how many wires you should have going to the ground...

 

[panamacruiser]

The automatic has the speed sensor the manual has a cable type...that being said, check ground or add an extra

 

[Will Thompson]

The automatic has the speed sensor the manual has a cable type...that being said, check ground or add an extra

all lc's 93+ have an electronic sensor manual or auto as far as i can gather? and you say add an extra ground from what i have read there was originally 3 wires i all ready have 4 ?

Remember it's not necessarily a broken wire, mine was a loose bolt holding the wire. (so tugging on it would made it seem like a good connection)

Normally it worked, but when the engine hit specific RPMs it would vibrate just right where it was completely losing connection at that frequency and, losing the ground generated a signal of a different frequency that mixed with the real one, resulting in pretty high readings on the ODO.

The problem could be worse on a diesel I think because it vibrates more, and the lower RPMs would result in a lower displayed reading.



For the sensor itself, it's hard to say. If it's the same as the autobox sensor (a sealed rotary encoder), then drowning it in oil wouldn't hurt anything.

If it's an inductive pickup sensor, then oil with metal shavings/powder would leave the metal on the magnetic tip and weaken/make the signal unpredictable. (that would on the internal side though, so I don't think that could be it).

Surly if your talking about higher readings on the mph gauge why is my odo working fine even though my clock isn't working properly surly it should be racking up more km's ? but its not i have had it on the gps and 1km is 1km. I am going to try and test the actual sensor and see if that's the problem, then i am at a serious dead end.

 

[Will Thompson]

Found the problem. Nothing to do with the sensor or the ground, pulled the clocks apart and a lot of burnt out and broken track, soldered a small wire across and it’s all good fingers crossed, probably only be a temp fix until I get the time to order a new clock. But for the time doing as long as it holds it can stay.

 

[Will Thompson]

I am back at square one with this, now i obviously know the fault. So this gauge was originally in KM's as its an import but its had an overlay put on it, i have found some new KM ones but there fairly pricey, my question is if i get a UK spec cluster from a wrecker will this all work and talk as it should ? or should i just buy a new original one and have it how it should be?