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The mkiv Supra Owners Club

Erratic Speedo


Mike_Mac

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I have just finished instaling a second-hand engine after my old one went belly-up.

 

The new engine was from a manual and I have swapped the loom from my old engine to this one, but am pretty sure all connectors were put on correctly. It runs and idles fine and seems good.

 

While I was waiting to source an engine I stripped and replaced my dash panels and fitted a UK speedo face. A quick test drive with the old engine in showed it to be reading correctly.

 

Now after installing the new engine my speedo is on the blink.

 

When driving it can jump from anything between 40-120 mph and can be made to do this when stationary by blipping the throttle. It seems to move almost proportionally to the amount of throttle. Occasionally it will read correctly, but will still jump around a bit when the throttle is applied. Yesterday it died completely and the odo stopped clocking the miles and lit up the master caution & engine management lights and caused the O/D light to flash. Today, however, it has begun working, but is still erratic. When it is working erratically the odo still records the km, so I don't think it's a dry solder problem with the odo.

 

I have removed my speedo converter thinking it had gone faulty and the problem remains unchanged. Reading the stored error codes gives 4-2, which seems to be no 1 speed sensor, but I can't understand how the speedo is reacting to the throttle. I have a feeling this code was logged when it died yesterday and the actual problem is something else.

 

Any ideas anyone?

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Can anyone point me to where the Speed sensor is, as my thinking so far is it's been disturbed during the swap.

 

EDIT: Found a picture, part number and wiring diagram, so as soon as I can get the car on a ramp I can check the connection and then order another sensor if needed. It can't be the wiring because the speedo still reads correctly at times, so it has to be sensor related.

 

The only other thing I can think of is the combination meter and I can borrow a J-Spec one to swap with if necessary.

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Chris - No TSD, or anything else fitted now - I returned the wiring to stock. Same behaviour both before and after removal. The ODO & Speedo now tend to stay dead rather than jump around.

 

I can't see the fault being in the speedo or ODO, as both will work fine at times. I think a connection in the feed from the no 1 speed sensor may be duff or loose, but I'm not too sure what route it takes before it reaches the dash.

 

There is also an occasional intermittant misfire which seems to occur once warm and happens all over the rev range. It will stagger for a while and then drive totally fine before doing it again later.

 

It's definitely not the plugs or connectors and I have a feeling it's an electrical connection on the loom, which may have been disturbed during the swap. I will check and tighten what I can get to tonight, but am not sure which connections and wires are relevent.

 

The annoying thing is the car drives great otherwise.

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