Hi,
I have just registered and already requesting for assistance.
I am having issues with my electronic cluster speedometer intermittent reading and needle fluctuating on my 1994 MR2 SW20 with E153 gearbox.  I have tried process of elimination as follows:
1.  Wired individual wiring from electronic speed sensor at engine to cluster on dash (success)
2.  Electrical pulse test on speed sensor using multi-meter (success)
3.  Connected speed sensor to adapter and driven by battery drill, all appears correct at the cluster (success)
4.  Plastic gear on speed sensor at 30 - 35, in working condition (28mm diameter and 30 teeth) in question if diameter is correct.
5.  Inspected Vehicle Speed Pulse Generator Drive Gear (blue coloured plastic helical gear) using mirror and light via access hole for speed sensor assembly (appears to be serviceable as it is rotating and what appears to be no sign of wear or damage) 
6.  Installed speed sensor assembly to gearbox without electric sensor cover to observe rotation of shaft (intermittent rotation) with engine running in gear on stands)
I would kindly like to request for additional suggestions on other possible causes for speedometer not working.  Would I have to remove the whole engine and gearbox assembly to replace the Generator Drive Gear or is it manageable to be done whilst engine and gearbox assembly is still in the vehicle.  
Many thanks and have a great day.
Miyagi 
 
 

Possible the capacitors in the gauge are bad? They get old and leak or overheat. This is a known problem for speedos but more specific to the RPM or Tacho gauge.

Hello Miyagi,
    As a MK1 MR2 enthusiast and having had a speedometer issue myself not too long ago I thought I'd put forward an idea for you.
 
With what you have tested and verified to be working it's highly possible that the speedo cable to gearbox is possibly not connected correctly.
 
I had an issue with mine where the speedo was jumping around ever so slightly and what I found was the following
 
The connection to the gearbox must be installed with the speedo cable indenture nodule lining up with the connection in the gearbox other wise it will most certainly not work correctly.
 
If that's correct then check that you have installed the connection down firm and tight ALL the way.  Mine once managed to wind it's way loose.  Tightening it up and checking verified  it worked just fine.
 
Failing these 2 check points, I'd be pulling out the speedo cable to check that it's not fraying etc as this will most certainly give you mixed and intermittent results.  Sadly they can wear out, especially if not installed correctly.  On that note, be sure that your speedo cable is routed as per Toyota standard manufacture.  Failure to do so can also lead to strange Speedo issues.
 
Hope one of these fix it points works and that you have your MR2 working perfectly as it always should be.
 
Drive on and continue to enjoy your MR2 Miyagi,
Sean.
(Spaceresearcher)
 

Spaceresearcher
Hello Miyagi,
    As a MK1 MR2 enthusiast and having had a speedometer issue myself not too long ago I thought I'd put forward an idea for you.
 
With what you have tested and verified to be working it's highly possible that the speedo cable to gearbox is possibly not connected correctly.
 
I had an issue with mine where the speedo was jumping around ever so slightly and what I found was the following
 
The connection to the gearbox must be installed with the speedo cable indenture nodule lining up with the connection in the gearbox other wise it will most certainly not work correctly.
 
If that's correct then check that you have installed the connection down firm and tight ALL the way.  Mine once managed to wind it's way loose.  Tightening it up and checking verified  it worked just fine.
 
Failing these 2 check points, I'd be pulling out the speedo cable to check that it's not fraying etc as this will most certainly give you mixed and intermittent results.  Sadly they can wear out, especially if not installed correctly.  On that note, be sure that your speedo cable is routed as per Toyota standard manufacture.  Failure to do so can also lead to strange Speedo issues.
 
Hope one of these fix it points works and that you have your MR2 working perfectly as it always should be.
 
Drive on and continue to enjoy your MR2 Miyagi,
Sean.
(Spaceresearcher)
 

His is electronic so the cable doesn't exist. It has a sender on the Gearbox and uses purple or purple with white wires to send the signal to the gauge then back to the ECU.

If instrument checks out (smooth operation) when spinning speed sensor with drill then it really points toward the engagement of the speed sensor to the blue plastic drive gear located on the diff. Only needs the slightest distortion of a tooth on that drive gear to cause the speedo needle to flick. Does the flick change in frequency as the speed increases ?  Gearbox has to be completely disassembled to change the plastic drive gear.
It is unusual for this to happen on an electronic speedo setup as there is very little load to drive the speed sensor.
Also be very careful running it in gear while up on stands. One foot hovering over brake pedal !!
And if wheels are removed do put some nuts back on to keep brake discs from flapping about.
Let us know how you get on with it.

Gents,
 
I hope that I've use the correct area to reply as I can't locate a reply button for individual responses.
First and foremost I appreciate all your prompt replies.
 
GDII
Thankyou. Initial attempt to rectify speedometer issue was to replace all associated damaged capacitors by a very knowledgeable MR2 friend.  Unfortunately issue continued.
 
SPACERESEARCHER
Thankyou. I'm operating an electronic speed sensor so no mechanical cable.
 
FALCON
Thankyou.  The fluctuation of the needle is inconsistent and indication of speed is also incorrect.  I should have also  mentioned that the vehicle originally had a mechanical speed sensor which upon removing I found that the plastic gear sub-assembly on shaft was damaged.  Therefore I decided to replace it with a used serviceable electronic speed sensor plastic gear 30-35, hence installing individual wires (with much knowledgeable assistance from my MR2 friend).  Yes, totally agree regarding the little load to drive the speed sensor should it originally was electronic sensor (which unfortunately I overlooked to mentioned that it use to be a mechanical drive) so damage may have already been done to the Blue plastic drive gear.  I can only assume that removing the gearbox could not be achieved whilst in the vehicle.  I appreciate your concern regarding working safely as I can assure you that I have place additional rated stands beneath the vehicle and on level footings.
 
Many thanks and have a great day.

The old mechanical cable drive seizes (usually the angle drive) and overloads the plastic gears.
Probably damaged the plastic gear on the diff. Doesn't take much.
Gearbox can be removed with engine in car but it's possibly better to lower engine and gearbox down to floor.
Much easier for aligning gearbox into clutch when reassembling. Less likely to ruin a brand new clutch and have to redo the whole lot again.
Then the gearbox has to be completely dismantled to get to the plastic drive gear on the diff.
That's quite a significant job too.

Engine out = PITA, so just a couple of thoughts:
 
I have recently fitted a 7" Android head unit that apart from all the other stuff on it also has a good reliable installed GPS program, and while driving I mostly have that app running so I can use the speed indication on it.
IMO it is probably easier to read than the OEM speedo that I now hardly ever look at.
The GPS is more accurate anyway, important when setting my cruise control so as not to exceed the speed limit in strict enforcement areas.
 
Another cheap, and simple alternative to the OEM speedo might be one of the better 'heads up units' (HUD).

Falcon
 
Gearbox can be removed with engine in car but it's possibly better to lower engine and gearbox down to floor.
Much easier for aligning gearbox into clutch when reassembling. Less likely to ruin a brand new clutch and have to redo the whole lot again.
 

Doug, yes important not to do that.
I don't know whether it would work with a turbo box, but when I refitted my S54  box with the engine still in the car, to get the right alignment I maneuvered the gearbox so that one at a time I could fit 4  temporary mounting bolts from the gearbox to the engine that were slightly longer than stock. 
This allowed the correct alignment with the gap between mounting flanges of the gearbox and engine large enough so that the input shaft and clutch splines were not yet engaged. I then simply slid the gearbox along the bolts till the shaft went in. But even then of course aligning the clutch splines was still a PITA.
But what a wonderful feeling when those flanges go together and you can refit the stock bolts.

Reddtarga
Thankyou for your response and suggestions. I'm currently still working on the vehicle in preparation to get it registered and yes I've ask the question regarding the installation of a GPS speedometer device, unfortunately the reply was NO.  Should I have to remove the box to repair the speedometer drive gear I'll would much prefer not having to remove the whole motor and gearbox assembly.